Balbir's Blog

Review: Sage Beginner's Guide (Fantastic Book on Sagemath)

2011-08-28T13:05:00.001+05:30

Sage Beginner's Guide is an introductory book for the Sage math software, an open source mathematics system. Sage is a free alternative to Mathematica, Maple, and Matlab. The book does a great job explaining the basics of Sage. Each chapter is well written with my favorite "Time for Action", that allows the reader to explore the software and understand the experiment in depth. It is a great way to explore how things work and completely in line with what the book says "learning by doing: less theory, more results".

The first chapter is a tour of "what can be done with Sage". The second chapter deals with installing Sage across a variety of platforms. Chapter three eases the user into the sage interface, it discusses how to use the CLI, the notebook interface and get help. Chapter four is all about python; the chapter does a great job introducing python: one of the best I've seen in a book. It arms the reader to work with Sage and python.

Chapter five focuses on vectors, matrices and linear algebra. Sage include numpy and the chapter covers numpy in good detail. Chapter six is my favorite. I love plotting graphs, the chapter discusses various types of plots. The chapter does a great job explaining Matplotlib. Chapter seven is all about symbolic mathematics: integrals, differentials, ODE's, solving equations, finding roots, Taylor series and more. Chapter eight is about solving problems numerically and for me this is the best chapter in the book. It covers a variety of topics -- finding roots, maxima and minima of functions, gradients, integration, discrete Fourier transforms, window functions, solving ODE's. linear programming, constrained optimization to probability. Chapters five to eight are the meat of the book and I expect all readers to keep referring back to these chapters time and again.

Chapter nine is about advanced python programming, but I was a little let down based on what I had seen in chapter four. The chapter covers OOP, modules, exception handling and unit testing. What I did not like was the way the code is formatted and occupies a majority of the contents of the chapter. Chapter ten is about my favorite tool, LaTeX, it covers integration of LaTeX and Sage. No mathematical software is complete unless one can build interactive workbooks and the author does a great job explaining how to go about that business with interactive graphics and good typesetting.

Given the capabilities of Sage, the book fails to cover some of the discrete mathematics aspects, like graph theory, combinatorics and cryptography. To be fair, the author does mention in the preface the focus is on calculus, ODE and linear algebra.

Sage is a beast with several projects integrated under a single umbrella. This book meets the goals it sets out to achieve and does so in an incredible manner with clear definition of chapter goals, good summaries and excellent examples. The breadth of coverage of topics is very good for an introductory book on Sage. If there is one book I could recommend on getting started with Sage, it would be this "Sage beginners guide"

Slingers - More Lasit's?

2011-05-13T23:25:00.000+05:30

In todays IPL match between Kings XI Punjab verus Kochi Tuskers, the Kochi blowers were seen imitating Lasit (Slinger) Malinga in their bowling action. Surprise, Surprise, is this going to become a trend soon?

Match fixing (WC 2011)

2011-04-30T19:38:00.000+05:30

I wonder if such controversies are created to make people believe that the losing team was too good for the opposition (winning team), but money got in the way.

Somehow, the WC 2011 win does not seem fixed, I remember seeing the joy on Mahela's face and the joy when the Srilankan's got to the half way mark. They thought they had won the match.

Allegations take away from the hard work of the players and glory. It sure is hard on players who are dedicated to the cause of their teams.

ATI driver 11.4 is out

2011-04-30T09:00:00.000+05:30

It is here works perfectly well with my Fedora 15, beta system. I hate moving away from the open source driver, but I've got to do so for thermal (probably) and speed reasons (6x). Mesa has some interesting changes, including support for direct3D, but for now it is time for me to experiment with OpenCL :)

Draft of Enumerative Combinatorics - volume I

2011-04-23T22:30:00.000+05:30

Richard P Stanley has the draft of the second edition available at http://www-math.mit.edu/~rstan/ec/ec1/. The book is a classic and highly recommended if you are interested in combinatorics. The book assumes advanced knowledge of mathematics (commutative integral domains, generating functions, etc). I am reading the first chapter and I've been ignoring some of the rigor to get the most from it.

Knuth's Earth Shaking Announcement

2011-03-18T23:24:00.000+05:30

I found the video here (http://river-valley.tv/tug-2010/an-earthshaking-announcement). It is quite awesome!! Earth shaking reminds me that I request all readers of this blog wish Japan all the very best as the country tries to cope with the enormous loss and devastation.

Kernel Mode Setting and Resolution

2011-02-23T18:45:00.000+05:30

The main pain of upgrading to rawhide on Fedora has always been -- "Hey, what about my proprietary graphics card support?". I've been bitten a few times. When I made the decision to buy a card, I chose ATI so that I can enjoy the benefits of a good open source driver.

Rawhide has moved to gnome 3, and gnome shell requires 3D graphics or falls back to the old style gnome. With kernel mode setting, there is sufficient support in the form of DRI/DRI2 and Mesa 3D to support OpenGL.

My main issue was getting the right resolution. Here is a well known way of solving the problem

Solution

Run the cvt(1) command, specify the resolution and refresh rate, it will output a set of mode lines. See http://www.arachnoid.com/modelines/ for a good tutorial on mode lines (NOTE: You might not need to do this if EDID works fine for you)
Modify /etc/X11/xorg.conf and add the following under the monitor section
Modeline "...." (whatever cvt output)
Option "PreferredMode" "Name of the mode used above"

This should get you going and help you come to the desired resolution

Solutions that did not work

Adding video=... at boot time
Disabling KMS, helps fix the resolution, but the correct 3D driver (mesa DRI) does not load, you are left to Software 3D emulation (that sucks)

Enjoy, I hope someday we'll get an open source driver for openCL :)

Distro Hopping

2011-01-26T13:05:00.001+05:30

After trying some more distros, I decided to move to debian part-time. I was surprised to see Linux Mint support debian (albeit only the "testing", also known as "Squeeze" release).

I am in love with the combination of mint and debian. The version of the kernel is still 2.6.32, but debian stability and support is rock solid. I'll slowly migrate to the experimental version when "Squeeze" is released.

The rich packaging and stability of debian with the front ending of the very best makes this a lovable distro.

I am posting some screenshots, enjoy!

Article on unmapped page control

2011-01-03T10:34:00.000+05:30

LWN.net published an article on the work I am doing, it is a great read, please see http://lwn.net/Articles/419713/

Happy New Year

2011-01-01T00:52:00.000+05:30

Here is a hearty wish for a happier 2011, may the new year bring more happiness, health and wealth.

I want to make more resolutions, even if I break them - my new year resolution :)

Internet struggle

2010-12-28T19:39:00.000+05:30

I've been taken back to my pre dsl days, thanks to the MTS MBlaze stick I recently acquired. The connection is best effort, speeds go down to a few bytes, forcing me to refresh a page at-least thrice before I can see it. All of this has made for a great vacation and bad experience. Sigh! I should have done much more research before acquiring a USB modem stick. I should probably move on to the 3G sticks available.

cgroup proposal for use in SLURM

2010-12-08T13:48:00.000+05:30

I came across the following slides about using cgroups with Slurm. Very exciting to see cgroups be used more widely. For those of you who missed it, there is also a long discussion on autogrouping using tty's.

FOSS.IN 2010 list of talks announced

2010-11-13T13:21:00.000+05:30

The final list is here http://foss.in/talks/final-list.html#more-1674

There are some very interesting talks, I am speaking on "Operating System Caches in a virtualized environment". Please do attend

Fedora 14 is out

2010-11-03T00:43:00.000+05:30

Get Fedora 14 from https://fedoraproject.org/get-fedora. The website has a great new look and feel, check out http://fedoraproject.org/.

Checkout some of the cool tools and features at http://fedoraproject.org/en/features/

libcgroup has been updated to 0.36.2, I'd recommend moving to 0.37 (it should be available soon)

I've been using Fedora for a long time and constantly since Fedora 11. I still remember seeing Fedora core 1 announced and Fedora core 2 shipped with the 2.6 kernel, wow! we've really come a long way! There is much more to cover.

libcgroup v0.37.rc released

2010-11-02T21:53:00.000+05:30

We just release libcgroup v0.37.rc after about five months of development. There are some really cool changes, lots of bug fixes

cgconfigparser supports quotes
lots of bug fixes for tools (cgget, lssubsys, etc)
cgsnapshot is a cool new tool!

The release is available from https://sourceforge.net/projects/libcg/files/

As usual the home page is at http://libcg.sourceforge.net/, the generated documentation is at http://libcg.sourceforge.net/html/index.html. The source code (git) is at http://libcg.git.sourceforge.net/git/gitweb.cgi?p=libcg/libcg;a=summary

Hack on!

Some cool feature of firefox 4

2010-10-24T23:49:00.001+05:30

firefox 4 is still under development, I've been testing it again now. A while back I tried it for its support of webgl, but I found gmail crashing and I submitted reports. I now see the new minefield (firefox 4) is quite awesome. What do I love about the new look

Group your tabs is a really cool feature
Refresh button has moved to the right
Book marking got a whole lot easier
When pointing to a hyperlinked item, the address bar shows what the URL of the linked item is (quite cool)
There is a new firefox sync in preferences to sync firefox across all devices
The web console looks interesting, but nothing to beat Chrome's developer tools

There are many more, these are what I could see from my first impression. I'll try and post some interesting screenshots. I've also heard that the firefox 4 javscript engine is now one of the fastest engines (really cool!)

On my wish list, I have

Better download manager
Ability to do private and non-private browsing in parallel

Having fun with libvirt and qemu

2010-10-23T19:24:00.000+05:30

I've been having some fun dealing with libvirt and qemu. qemu is the basic hypervisor that creates a virtual environment for execution and libvirt is the overall management library. libvirt has several checks built in to valid qemu and every-time, qemu changes (major version), libvirt fails or the default configuration needs tweaking (XML file).

Both are great projects, it is interesting to understand their architecture (which of course is way deeper than this post :))

Cgroups in use

2010-10-22T08:56:00.002+05:30

I stumbled upon slides from the 2010 RedHat summit. Cgroups and Resource Management is introduced and mentioned.

There is also a great video on cgroups, really nice to see technology developed being exploited. The video is crisp and clear, do watch it now

Plumbers talk on memory cgroup

2010-10-22T08:20:00.000+05:30

There have been several talks on memory cgroups in the past, I just found out about a new one at Linux plumbers by Ying Han from google. If you are at plumbers, I'd recommend attending her session

Signal processing in sagemath

2010-10-17T12:03:00.000+05:30

I was experimenting with some tools for signal processing. The first tools that come to mind are opensource tools scilab and octave. I spent a day looking at the tools, the UI. I figured I could do definite integrals quite easily. Having spent the day and not having the made the progress I would have liked to, I turned to sagemath.

My first delight was to learn about piecewise functions. I decided to play with a square wave of time period 20.

I started with a function that looked like

f1(x) = 1
f2(x) = 0
f = Piecewise([[(0,10),f1],[(10,20),f2]])

Plotting the function with plot(f) showed

Which is exactly what I wanted. Piecewise class also supports a number of very useful functions related to fourier series.

One particularly useful one is a plot fourier series partial sum. The function shows how as we add more frequencies the fourier approximation to the original wave gets better

I started with

f.plot_fourier_series_partial_sum(5,10,-20, 20)

f.plot_fourier_series_partial_sum(15,10,-20, 20) gave me

f.plot_fourier_series_partial_sum(150,10,-20, 20) gave me

This looks like a good approximation to the wave we started with and almost looks like the signals I got on my oscilloscope during my engineering days :)

The next important thing was to get the sine and cosine coefficients

print "sine terms"
for j in range(0,21):
pretty_print(f.fourier_series_sine_coefficient(j, 10))
print "cosine terms"
for j in range(0,21):
pretty_print(f.fourier_series_cosine_coefficient(j, 10))

sine terms
0
2/pi
0
2/3/pi
0
2/5/pi
0
2/7/pi
0
2/9/pi
0
2/11/pi
0
2/13/pi
0
2/15/pi
0
2/17/pi
0
2/19/pi
0
cosine terms
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0

Overall, I had good day with sagemath. I need to experiment with some of the discrete functions. Keep tuned in, I'll try and keep you updated on how it goes.

OLS 2010 proceedings

2010-09-11T01:23:00.000+05:30

The draft proceedings are at http://www.linuxsymposium.org/LS_2010_Proceedings_Draft.pdf

I am quite excited about http://www.linuxplumbersconf.org/2010/ocw/events/LPC2010/proposals, but unfortunately I won't be able to attend this year. The other exciting event was KVM forum, I could not attend, but I am glad the proceedings are available http://www.linux-kvm.org/page/KVM_Forum_2010

Article in LFY

2010-09-10T23:28:00.000+05:30

In this months issue of Linux For You, here is the abstract - I hope to continue to adding to this series of articles.

Power Programming—Bitwise Tips and Tricks
If you are a seasoned programmer, these tips and tricks will seem very familiar, and are probably already part of your repertoire. If you’re a novice programmer or a student, they should help you experience an “Aha!” moment. Independent of what you currently do, these tips and tricks will remind you of the wonderful discoveries in computer science, and the brilliant men and women behind them.

Quote for the day

2010-08-02T23:51:00.000+05:30

The Art of Software Development is the tussle between being generic and specific. Generic at the time of writing and specific at the time of execution and vice-versa.

Balbir Singh

Quote for the day

2010-07-31T00:56:00.000+05:30

Todoing... The art of catching up with TODO's, but never finishing them!

Balbir Singh

Heading to OLS

2010-07-10T22:32:00.001+05:30

It is that time of the year again, I am heading out to Ottawa Linux Symposium (http://www.linuxsymposium.org/2010/schedule.php), I am giving a talk on Page and Slab cache control in a virtual environment. I also look forward to meeting Paul Turner, Ying Han both of google to discuss cgroups (scheduler and memory). This year again there are loads of interesting presentations from Phase Change Memory to virtFS and beyond.

If you are coming over, it'll be really nice to see you there

Things shook with pulseaudio

2010-06-13T01:34:00.001+05:30

I had a interesting night as I tried to watch the wonderful USA versus UK soccer world cup match and debug sound on my Fedora 13 box. I tried executing the following command "paplay -v /usr/share/sounds/KDE_Window_Close.wav" as my monitor and chair shook. I got off and it happened again.

My sleepy eyes told me something was not correct, my brain told me it is pulseaudio shaking the room with the sound, but my ears did not agree. Well I guess we'll know what happened in the morning, was it a quake, who won the soccer match and will pulse audio work as expected?

India Win Hockey Tournament

2010-05-17T00:26:00.000+05:30

India and South Korea were named joint winners after rains washed out the match. Good to see the changes in the Indian hockey team working well. Congratulations!!

Just as I write this, England have beaten Australia to win the World T20 world cup!

Wow! What a week of surprises. I wonder if the football world-cup will hold some interesting surprises as well.

Blog from a standalone client

2010-03-19T03:03:00.001+05:30

I am giving a shot at posting this blog entry from a standalone client. Like it very much, quite cool and awesome.

I also like that I can bold, italicize, underline, ~~increase~~ font size,

number items
Who is number two?

bullet them

bullets, like sub-bullets

So much more easily. There is also tables, pictures, etc, but I’ll get to them slowly.

Open source blows my mind again

2010-03-12T13:55:00.004+05:30

I wrote the configuration parser for libcg sometime back. Dhaval helped make significant improvements to it as well. At the time we wrote it, I had imagined we would probably create about 20 or so groups, but I planned ahead and "hard coded" the limit to create 1024 groups. How forward thinking of me :)

This morning I got a message in my inbox that said

"I'm using cgroups for lots and lots of users per server (2.000 or more).The problem is, I'm using one cgroup per user (for memory reasons)." See http://permalink.gmane.org/gmane.comp.lib.libcg.devel/1737

I was surprised to see that someone wanted to create so many cgroups, my first reaction was "Oh! my god" I hope we don't have a major bug in functionality or scalability.

I looked at the code and asked for counter that controls maximum number of groups to be scaled to something like 2048, hoping that the code would work, here is what I heard back.

"Yes!!! Thank you very much.. Its working now.. 37 thousand lines, 1400users (one cgroup for each user) :D Server is up and running now :D". See http://permalink.gmane.org/gmane.comp.lib.libcg.devel/1744

They use memory cgroups in their setup both hard and soft limits, so kudos for testing the whole solution. I never expected that we would be able to parse those many lines and support that sort of a configuration. This is where open source wins, I was able to provide a solution in seconds and I am hoping more feedback from the end users will help drive all the technology they use and I develop in the right direction. Had our software not worked well, we would have fixed it to enable the end user at the earliest.

Open Source blows my mind again and again!

Published an article in Linux For you

2010-01-22T21:14:00.004+05:30

You can see the abstract below

Developers
Introducing Kernel Samepage Merging
The motivation of KSM comes from the observation that on a large machine running several virtual machines (potentially running the same OS), there are a number of duplicate pages, each consuming a page of memory in the hypervisor.

The URL for the magazine is http://lfymag.com/currentissue.asp?id=13

Go rush and get the January 2010 copy, comments, feedback, criticism always appreciated!

FOSS.IN 2009 was great

2010-01-22T20:42:00.002+05:30

I am delinquent in reporting about my FOSS.IN experience this year. Nevertheless, better late than never! My summary goes, the good, the awesome, the excellent and the let-downs. For the photo stream check out "foss.in/2009" tag on flickr

The let-downs

There were very good talks, I spoke as well (see http://foss.in/2009/schedules/talkdetailspub.php?talkid=15), but I was surprised to see people who had never contributed code, presenting, even though that is something that FOSS.IN was trying to move away from.
Atul stepped down as the organizer or key-organizer of FOSS.IN. We've had some interesting discussions on the mailing list, I'll certainly miss those
Stalls - the stalls from Nokia and some of the student stalls were awesome, I was hoping to see some key innovative work happening
Goody bag - I did not get my goody bag, I asked early and I was told to come at the end, but I was told they ran out :( I missed out on the mug I admire soooooo much
FOSS.IN almost seeming like FOSS.DE (we need a stronger rotation policy :), just kidding on this one)

The good

I loved the spirit of FOSS.IN
Loved the environment and speaking to the volunteers
Pulseaudio, I typically and still to some extent don't like Pulseaudio, but the technology and the architecture I learnt from the learned, seem very impressive
The hobby electronics group and their project

The excellent

The workouts were excellent, the BoFS and many workouts had more focus
The rock music by the Raghu Dixit Project
Met some free lancers using Linux, they did not have stalls, but their projects sounded very exciting
The participants were serious about what they wanted to work on, which is very exciting to see
Networking and spending time with people

The awesome

The food arrangement, Hallimane

Hmmm.. Did I just put my neck out and at the same time be lazy? BTW, I wrote my Linux For You article while attending the conference :)

Some photos from FOSS.IN 2009 (more to come)

2009-12-06T13:33:00.002+05:30

I've not yet had the time to sit down and write a report and my experience, but here are some photos

From James Morris at Flickr

From Kishore Bhargava at Flickr

The entire set that Kishore has can be accessed here

Thought for the day in Hindi

2009-12-06T11:22:00.000+05:30

जो याद नहीं उसे भोल गए हम
जिसे भूल गए उसका नहीं गम!

Gops views on Mumbai 26/11

2009-11-27T18:52:00.002+05:30

Well worth a read! We've had lot of heros, lets remember and pray for them, the victims and their families and that such things don't repeat themselves anywhere in the world.

Smooth upgrade to F12

2009-11-20T19:01:00.002+05:30

My first post after the upgrade. The upgrade sailed through smoothly and I got back the packages I had to uninstall. The first issue I faced was the nomodeset issue. X would not recognize any resolution beyond "800x600", I had to pass nomodeset as kernel boot parameter to get my original resolution back.

I was also happy to see my back for resource counter scalability included in F12
(run rpm -q --changelog kernel | less)
* Mon Oct 12 2009 Kyle McMartin 2.6.31.4-75.rc2
- improve-resource-counter-scalability.patch: Fix scalability issues
on big machines, requested by prarit.

I am all set to sail, kudos to those who helped make Fedora and especially the upgrade path so smooth.

Upgrade Journey to Fedora 12

2009-11-18T22:47:00.003+05:30

After reading the ever so useful YumUpgradeFaq, I've started upgrading my system from F11 to F12. I had some scarifies to make along the way, I had to remove about 100 of my favourite RPMS, so that the upgrade starts

yum finally told me...

Transaction Summary

=======================

Install 238 Package(s)

Upgrade 4512 Package(s)

Remove 4 Package(s)

Reinstall 0 Package(s)

Downgrade 0 Package(s)

Total download size: 5.0 G

Is this ok [y/N]:

Wish me luck!

Fedora 12 is out

2009-11-18T07:09:00.005+05:30

I use Fedora on my desktop, now more than ever. I am currently well setup on Fedora 11, with 3D graphics (yeah, I can get Secondlife, google earth, etc to work with great speed) setup. Setting up 3D graphics was not easy (but that should be another blog entry. I also have my favourite sound system ALSA setup. I could never get used to Pulseaudio or get it to work the way I like. I am still trying to get webgl to work on my browser. The features in Fedora 12 are too tempting and of course I am already using some of the latest features via rawhide.

I guess its time to plunge into Fedora 12! Do take a look at the release tour of Fedora 12.

Thought for the day (Hindi)

2009-11-17T20:27:00.002+05:30

मैं अकेला ही चला था जानिब-ऐ-मंजिल मगर, लोग साथ आते गए और कारवाँ बंता गया

मजरूह सुल्तानपुरी

Great Knock Dravid!

2009-11-17T00:59:00.002+05:30

(From: cricket.yahoo.com)

Todays knock by Dravid's got to be the best I've remembered from anyone in a long long time. I've witnessed the record breaking knock with Laxman to help India win against Australia in India, the 200 odd to help India win against Australia in Australia.

I loved this one because of the determination and absolutely wonderful confident stroke play. This knock also got Dravid in the 11,000+ squad (only the 5th cricketer to have that honour). Bravo on the six, the quality of shots and the confidence. Keep the aggression coming Dravid! I love it!

Interesting memory cgroup controller links

2009-11-16T21:35:00.003+05:30

Here are some interesting links on memory cgroup that I found online (NOTE: I've not referred to my own papers)

NOTE: This is just a partial list of references.

Bangalore book fair 2009

2009-11-10T23:54:00.000+05:30

The Bangalore Book Fair has started today at Palace grounds and I happened to visit today. With close to 330 stalls, I was awed by all the books and publications present. I had two clear priorities

Technical books
Childrens books

On the technical front, I purchased

It was really nice to see a good number of exciting books for children, I even managed to find some interesting gifts for children I know.

I'd highly recommend visiting the fair, the last day is November 15th

Thought for the day

2009-11-08T21:25:00.002+05:30

Happiness is when what we think, what we say and what we do are in complete harmony

Mahatma Gandhi

Arguing about OS'es

2009-11-08T12:12:00.006+05:30

Gopal and I argued about Linux, Windows and browsing (nothing out of the ordinary though, we kill time in arguments and we've mastered that art). I thought I'd share what the stats look like for visitors on my blog. If you are worried about being profiled, don't worry, no personal information is stored by me! The data is from sitemeter and blogspot (If you are too concerned, you can start using the "Private browsing" or Incognito Windows)

Browser Share

Operating system share

FOSS.IN first shortlist

2009-11-08T12:04:00.003+05:30

The shortlisted talks, workouts, project of the day, etc are announced. This year seems to be quite interesting with several kernel talks selected. I am looking forward to the Pulseaudio, security, S.M.A.R.T., kernel, gnome, GSM/Telecom, Haskell talks. I wish to attend them all assuming there will be no conflicts :)

Exponentiation

2009-11-08T09:36:00.010+05:30

There are several well known exponentiation algorithms, but this one caught my eye, specifically due to its application in the Rabin-Miller primality test. Here is the math, the algorithm will follow later

Let the problem be rewritten as raise x to the power n. Let us convert n to binary

Where b0, b1, b2.. bk is the binary representation. Now lets rewrite x to the power n as

This in turn is equal to

The trick is to note that we need to compute even powers of x and determine b0, b1, .. bk. A simple trick is to, check if b0 is odd or even, if it is odd, multiply the current temporary value with x, if it is even, skip b0, but keep squaring the current exponent. Note we keep shifting n right, so that b1, b2,.. ,bk move to position b0 eventually.

Here is the algorithm from Sahni's textbook

def exponent(x, n):
 m = n
 expx = x
 power = 1

 while (m > 0):
     while ((m % 2) == 0):
         expx = expx * expx
         m = m >> 1

     m = m - 1
     power = power * expx

 return power

FOSS.IN posters are out

2009-11-02T12:39:00.002+05:30

This is some of the best creative work I've seen (in terms of conference posters and getting the message out). All of this is released under CC. Excellent work guys! I am reproducing them below, the original post is at Posters! Posters! We need them, crave them

A consumer complains

2009-10-30T12:28:00.001+05:30

I recently bought a new laptop and the display went bad in less than 15 days. I eventually got it back with the LCD replaced, but my experience at the customer service was horrible and I complained. Here is the letter I wrote, I am hoping that [company] will wake up and take notice. Customer service offered elsewhere (outside India) seems to be much more superior with value for customers.

My experience with [company] today was one of the worst I've had with any product support. I visited [service center] to repair my 15 day old laptop, the display had stopped working. I found that the front desk person opened my laptop without using any static protection mechanism, which I escalated all the way to [somename] (Customer Service Head). I asked for a letter of apology for not following prescribed procedure. [somename] told me it is a human error and I need to ignore it and stop interfering with how [company] service people work (I as a customer was going beyond my boundaries and interfering with their day to day work). After my complaint, the other people started doing the right thing, the local manager said that his employees were tired and just had lunch (hence the error). If [company] can void my warranty (even for opening my laptop, even though I did not (just hypothetically)), why is it OK for [company] service people to *NOT HANDLE* my laptop carefully.

Clearly I am very disappointed and want to see justice done in this matter. All I want so far is a letter of apology for not handling my product and a guarantee that their action has not damaged my laptop

Do you have any experiences to share? Consumer rights are taken for granted and I wish we could be more empowered to take stronger action.

FOSS.IN 2009 coming your way

2009-10-26T00:27:00.003+05:30

I know this is last minute, but the CFP is due tomorrow (so please make full use of the last day to submit proposals). The event has unfortunately moved out of IISc (my favourite venue for the event and given the proximity to my house, my favourite visiting place as well). Nevertheless, the organizers are very helpful/cheerful people and I get to meet a lot of local FOSS people, apart from the regular visitors. Make sure you attend the event if you are in town or make plans to come down to attend it.

Finite Automate - solution part I

2009-10-23T19:48:00.005+05:30

In my previous post "Finite Automata", I had posted two interesting exercises from well know texts. This post has their graphical solutions

Question 1 was

Given a binary stream, can we develop a finite automata to calculate the binary number modulo 5?

Here is the graphical solution of the problem, one can simulate an input stream of 0's and 1's and verify the correctness

The start state is represented using a triangle and the accept state is represented by double boundary node. In this case both the start and accept state is "1".

Question 2 was

Can we develop a finite automata that can validate the addition of two streams of binary numbers? Does such a finite automata exist?

There is one simplification we need to make to validate our results. For a given input of the form

0 1 1 <- Input1
0 0 1 <- Input2
1 0 0 <- Output

We need to present the string to the automata in the form [1 0 0][0 0 1][0 1 1]. We split the input and output into groups of threes, the last bit (MSB) represents the output. So for example, it says 1+1 is 0 and that is carried over and for the next input 1+0+ 1 (carry) is 0 and1 is carried over again. For the final input 0+0+1(carry) is 1. Hence this language is accepted by the finite automate.

Here is the graphical representation of the solution. In the next blog on FA, I'll discuss the techniques behind these solutions (which are probably very obvious to the reader of this blog anyway)

NOTE: states 7 and 8 are no good, but they are still shown here. Again, 3 is the start state and 3 and 4 are the accept states. The solution can be verified using two inputs and the output in the format specified above

Finite Automata (post one of many to come)

2009-10-23T02:23:00.002+05:30

Oh! Gosh I can see it already, this is going to be a long post. Here is a brief background, I recently found my copy of Michael Sipser's Introduction to the Theory of Computation lying around. I found that is was rather nice to read (compared to some of the earlier texts I had been reading) and on finishing the first chapter stumbled upon some interesting problems posed in different forms in Sipser's, Ullman's and Papadimitriou's book.

I am going to cover some interesting aspects of Automata in this blog entry

The exercises in this blog entry to provoke some thought
Their solutions and representation in the next blog entry
A software to help solve/validate some of the solutions to the exercises

The exercises I am going to cover are

Given a binary stream, can we develop a finite automata to calculate the binary number modulo 5?
Can we develop a finite automata that can validate the addition of two streams of binary numbers? Does such a finite automata exist?

Now that you have some food for thought, come back here and check to see what I did with these problems/exercises at little later in the next blog post

Thought for the day

2009-10-03T17:47:00.002+05:30

I satisfy myself by saying, "My every attempt at failing to solve a problem and learning from it, is equivalent to Edison trying a new filament" :)

Balbir Singh

Thought for the day

2009-08-21T19:55:00.002+05:30

Be willing to be questioned till the right thought emerges and be willing to question till the right answer emerges

Balbir Singh

Feeling insecure - thoughts on SELinux

2009-08-19T01:38:00.000+05:30

I've decided to run Fedora on my main desktop and enable other distros via virtualization. Yes, too many good solutions to ignore and I paid for the hardware. Anyway, this is not an entry about virtualization, but on SELinux. Fedora enables SELinux by default and I was left to live with the consequences. To try and make sure I get the same five star security on my desktop that enterprise applications get, I decided not to add selinux=0 to the boot command prompt.

I thought I could learn it, wouldn't I be an inferior being if I could not? What does it say about my go-getter attitude? My first encounter with SELinux was when I tried to get ~user/public_html enabled via the Apache Web Server. After I had followed the documentation, I still could not get a seemingly easy feature to work. I dig the web and without knowing too much, I learn about a certain context httpd_user_context_t and use a certain tool and it worked!!!

I had a grin on my face for a few days, I was going to be able to work with SELinux. My next surprise came when I tried to install some software and setroubleshootd very gently pointed me to the cause of the security violation while installing the software and what I could do to fix it (gee, an automated tool, no more worries). My next encouter occurred when I tried to install mediawiki with math enabled (yeah.. I decided to save paper and take notes on the wiki with TeX enabled, but that is a different story). Again, no matter how well I followed the guidelines, I could not get texvc to work :(

Remember to look at /var/log/audit files as root and run audit2allow to get some useful hints with SELinux. SELinux comes with a set of rich GUI tools, be sure to use them as you walk through the seemingly friendly maze of SELinux

I found some help on the mediawiki site that gave me instructions on how to setup SELinux and mediawiki together. To my surprise, I found quite a few software vendors providing additional instructions for setup when SELinux is enabled.

The feeling of being miserable at SELinux set in, I had to now read up and understand the architecture or forgo my new found security infrastructure. Today, I came across a very interesting web page (the wikipedia entry for SELinux),

“...given the threat models and capabilities of the adversaries involved, that's probably appropriate... But that’s not necessarily appropriate for all users. SELINUX is so horrible to use, that after wasting a large amount of time enabling it and then watching all of my applications die a horrible death since they didn't have the appropriate hand-crafted security policy, caused me to swear off of it. For me, given my threat model and how much my time is worth, life is too short for SELinux.” — Theodore Ts’o

You can only imagine how relieved I was to see this quote

Life is too short for SELinux

I was not alone, others hated it and found it hard to use as well. How pathetic can such happiness be, but I was overjoyed, excited to say the least.

My path forward is to continue to use SELinux, but be less tolerant of its idiosyncrasies. I am working my way through the documentation, but very slowly. I've learnt that my new best friend is "Z". Add "Z" to existing commands in Fedora and magically it shows SELinux information that can be a life saviour at times.

Search engine, BIOS updates and a waste of time

2009-07-26T01:02:00.002+05:30

I am not quite sure how, but the default search engine on my Windows partition changed to "Ask". I was looking for BIOS updates as a possible workaround to some 3D graphic issues I was observing. The search showed a wrong version of the BIOS and board and I (being me) ran the .exe express update only to realize that I've managed to erase out my Intel Management Agent firmware. The BIOS worked, but I could no longer read the temperature and voltage from the motherboard sensors.

After this blunder, the regular express or ISO based mechanism of BIOS update refused to work. Thanks to the recovery BIOS mechanism on my Intel board, I removed the jumper pins (see manual for your BIOS), put in the CD with .bio file burnt on it.

NOTE:

.bio is the recover BIOS. Burning
.bio from Windows burner created a UDF filesystem on the CD, which the failed to work.

I had to force a iso9660 file format from my Linux partition and recover. After the recovery BIOS update, I put back the jumper pins and got back to normal work. My Intel 3D graphics problem on Linux is not yet completely gone, but I do hope to debug it more and not hear back (update BIOS) when I ask for help

In summary, stop believing your search results if you want to be productive :)

No.. I've not given up blogging

2009-06-08T22:12:00.002+05:30

Just too busy collecting stuff to write about. Many interesting things, many learning's, mistakes and successes. Watch out, something might be coming soon.

I've got a twitter home as well, but twitter is like a light snack and blogging is like a full meal.

Negative Binomial Coefficient

2008-12-25T14:25:00.013+05:30

While reading through a book on probability and calculating the expectation of geometric series, I came across an interesting sum
We know that if then the sum converges to

Coming from the other side and using binomial theorem we getwhich expands to

Which leads to an interesting conclusion

I got maxima to verify this by calling the binomial function for various combinations of -1 and n. I am a little confused about the interpretation of the meaning though

Usually nC2 is used to imply from "n" objects, choose 2 at a time. nC2 gives us the number of total such combinations. What does -1Cn mean? What are the other proofs for -1Cn?

MUST READ: The Last Lecture

2008-12-20T20:40:00.003+05:30

I first heard of the book when I was traveling to a conference with a colleague who wanted to read the book, but wanted to find the best place to buy it. He briefly mentioned what the book was about, which I quickly forgot. I saw it again at several places, until I finally bought it from Strand bookshop in Bangalore. The most famous quote from the book is

“We cannot change the cards we are dealt, just how we play the hand.”
--Randy Pausch

This is one of the few books that I've had several people in my family read partially and love it (they are waiting to finish the full book). The book is about childhood dreams, how to achieve them and also goes a step further and talks about how to help others achieve their dreams.

The book is spectacularly well written, when you begin feel sad for Randy (the Author), there is a twist that will make you feel proud of the way Randy handled himself. The book is about positivity, about never giving up, about believing in humanity, in being true, about family values, about the good in the world, with sometimes what cannot be controlled and must be accepted.

Don't pick this book up as a pity book for Randy, you'll be left pitying yourself after reading everything that Randy did and how he lived his life, leaving us pondering if we've made the best use of our time. Randy focuses on family values, his students, his mentors, his family and there is not a single negative sentiment that he passes on to the readers.

If you are feeling depressed or need something good and small to read, something to boost your moral, to rebuild faith, to appreciate life and the people around you, you must read "The Last Lecture"

Dhoni's belief in Dravid

2008-12-19T11:35:00.002+05:30

I like Dhoni's attitude, he said two important things

Demoting him will put pressure on him, since 3 or 4 wickets would have fallen when he comes in
He is a good player, who needs some time in the middle

That is again a sign of good captaincy. Dravid, wake up, shake up, cricket calls!

FOSS.IN (part 2)

2008-12-16T18:58:00.003+05:30

In continuation from FOSS.IN (part I)

Photo by Sony Phil

The first keynote was from Harald Welte. The keynote was about embedded devices, manufacturers and proprietary Linux trees and their complete ignorance or lack of enthusiasm to contribute upstream. The presentation had information about how vendors were still using old obsolete Linux trees, which had several security flaws and the fixes were not being provided to users. The last keynote was from Kalyan Verma. Unlike the first keynote that lacked a single illustration, this one was full of award winning pictures, FOSS principles applied to other professions and life and also about the environment. How a cup of tea is playing its part in hurting the environment and the stress that we as humans and our requirements is putting on nature. Kalyan also spoke about his previous job as a security expert at Yahoo. He spoke about how cryptography makes no sense and there were obvious security flaws in most implementations. I disagree with Kalyan on some of the things he said about cryptography (like it makes no sense). I think what Kalyan was alluding to, but failed to say was that, security is only as good as the weakest link (a fact known to almost all programmers by now).

Kalyan mentioned that putting up his photographs under creative commons has gone a long way in helping his career. Since the pictures were free to download, they were shared under creative commons, which lead to newer opportunities and work. He went on to say, Pictures are a remarkable form of art. The more you look at them, the more you admire them, which is why sharing his pictures brought in more work and money.

Do check his photographs, they are really cool! James has a good coverage of his keynote as well.

The FOSS.IN team put out a video documentary covering their aspiration for their event and what was achieved. I'd say with FOSS.IN 2008, we've headed in the right direction, probably lost a few people along the way, but we are headed in the right direction. A technical event such as FOSS.IN should focus on contributions and try to encourage and build the mind share for it. Such a direction requires time and patience and also a lot of will power from both attendees and the organizers. We had a drastic change in sponsors this year, but we had them nevertheless, without whom such a large scale operation is hard to carry out.

The food, lunch and snacks were excellent, again James covered it well with photographs and other photographs marked foss.in on flickr. Here are some more memories from FOSS.IN 2008

Photo by Sony Phil

Photo by James Morris

From mdemon

From Sony Phil, photograph from the libcgroup workout

Lagrange's interpretation in python

2008-12-07T00:31:00.009+05:30

I've been reading up on Fast Fourier Transform (FFT) from several books on algorithms that I have, TCLR, Tamassia, Sahni, Numerical Recipes, a big set of DSP books. Several of these books focus on interpolation before touching upon the subject of FFT. My favourite book so far for numerical algorithms is R.W. Hamming's Numerical Methods for Scientists and Engineers, Second Edition, Dover publication. Chapter 14, touches upon this topic. I love his explanation and illustration of interpolation versus extrapolation. Thinking along that subject, I decided to do some implementation of my own for interpolation. Sahni (Computer algorithms in C++) has an understandable implementation of the algorithm. The biggest drawback was implementing my own polynomial class. This is where, I think Python scores. I found that SciPy implements a polynomial class.

Here is the code for interpolation

def lagrange(x):
tmp = scipy.poly1d([0])
result=scipy.poly1d([0])

for i in x.keys():
 numerator=scipy.poly1d([1])
 denom = 1.0
 for j in x.keys():
  if (i != j):
   tmp = scipy.poly1d([1,-j])
   numerator = numerator * tmp
   denom = denom * (i - j)
 tmp = (numerator/denom) * x.get(i)
 result = result + tmp

return result

input = {0:5, 1:10, 2:21}
print lagrange(input)

NOTE: Blogger keeps messing up my indentation, I am yet to figure out why.

Sahni's input for the example is {0:1, 1:10, 2:21} and I was surprised to see my program return a different output. Fixing the input, showed the correct results. That reminds me, somebody please ask Sahni to start maintaining useful errata for his books. I searched on the web and found nothing useful.

Running the same algorithm on y = log(x) and input = {1:0, 2:0.3010, 3:0.4771, 4:0.6021}, gave me 00.0123 x^3 - 0.1362 x^2 + 0.6236 x - 0.4997, which corresponds to the cubical approximation of log x (R W Hamming, page 233).

FOSS.IN 2008 Report (Part I)

2008-12-05T22:27:00.006+05:30

FOSS.IN was an event I usually attended, last year I co-presented and this year presented and held a workshop at. I've been meaning to display promotional content on my blog

But... I could not :(

Anyway, the story is not over, even though foss.in for 2008 is. The promos show clearly what the organizers had in mind. I must admit that the organizers make me nervous with the schedule, with selected talks being announced about three weeks before the final event, when I was on vacation. The schedule and slides can be found here. I presented on control groups and organized a workout for libcgroup. Both were well received with significant queries at the end of the talk and good workout participation. We got several patches posted during the workout and after. The workout plan and updates are here.

One of the things we did well this year, was the kernel hacker day at foss.in and followed it up with a successful workout. We had a good number of people come and talk to us about the kernel, their intention to contribute and the issues they face. We admittedly had a plan 9 fan, apart from Christoph Hellwig. There were lightening talks and I spoke about my ideas on building a threaded RB tree for Linux.

Kernel Hacker Gathering (Photo by James Morris as seen on flickr)

There are some fun photos, that several people took. Kushal from Fedora took some very nice ones. He was kind enough to photograph all women and leave me out. Needless to say Kushal, you owe me a T-shirt and I want it now! James Morris, did a good job of taking photographs as well.

(Photo by James Morris as seen on flickr)

(Photo by James Morris as seen on flickr)

One thing that did catch my attention was my T-Shirt with my name on it. I love the T-Shirt and hope it stops choking me, when I wear it, someday :)

Speaker T-Shirts (Thanks, well done guys!!)

I was caught working, I could show the code if needed!

You can find James' photo set here.

Lets step back, the event began with a video from team FOSS.IN

Atul has always been a good speaker, he began by explaining the motivation for the change this year and ate an Apple on the stage, claiming that it was only low hanging fruit in the conference and he ate it :) Unfortunately for Atul, we provided other low hanging fruits to developers and allowed people to contribute, even if the contribution was trivial. In the longer run, as foss.in proceeds year and year, I think we'll find the low hanging fruits disappear as the developers mature and our contributions mature.

I'll update on the keynotes, the other speakers and more interesting stuff in part II, stay tuned.

Having a bad day?

2008-11-18T20:29:00.003+05:30

Have you ever had a feeling of a bad day. Days that you wish would either bring some good news or just end or if possible never started. We'll such days are definitely hidden in every month, every year and in our life. Believe it or not, one will strike it when you least expect it. One needs to learn to get through such days and even fight day. Fight back a day? Yes, it is possible

Be nice and assertive to the most annoying people around you
Don't show on your face that you are annoyed, wear a smile
Remember bad days can end quickly if you are positive and will last for ever if your attitude is negative
Learn from your bad days, analyze to see what you could have done differently to make them end faster
Help others around you have a good day, even if you are having a bad day (of course not at your own cost)

Fight back and take bad days away from your life. Remember life is too short to have bad days in them.

Bank of San Serriffe (with branches in Blefuscu and Elbonia on the planet Pincus)

2008-11-07T16:19:00.003+05:30

Knuth has decided to stop sending personal checks, due to his discovery of a financial fiasco. I've have one hexadecimal dollar in the bank. The list of all people who have money in the bank can be found here.

Time out, take a break, Dravid!

2008-11-06T12:38:00.002+05:30

(Photo from http://content-usa.cricinfo.com/indvaus2008/content/current/player/28114.html)

Dravid's dismal form continues in test cricket. He is already out of the one-day squad. When Dravid resigned as captain, he did so to focus on his batting. Unfortunately, Royal Challengers did not work for him (despite his good innings towards the end, when the challenge was already over). His test cricket form has also gone bad. I think it is time to hand Dravid the Ganguly treatment. Drop him from the squad and get him to make a comeback. This is the same thing he and Chappel did to Ganguly and it seemed to work well. I don't want to rule out Dravid for the future, but he seems to be holding up a place that he needs to deserve again. He has a lot of cricket left in him. Seeing his mates Ganguly and Anil must make him nervous, but he should look at Tendulkar for inspiration.

The best way to get back to form is to play domestic cricket and make a good comeback. I hope Dravid will realize that a break is in his favour and the selectors will hand him one.

The world economy, history and more

2008-10-11T19:04:00.002+05:30

Looking through the great depression in the stock market reminds me of the 2001-2002 days, when the web commerce bubble burst and a recession was on our hands. Are we looking at a recession, we'll from my point of view and many others we are already in it; in fact we are in a worse state. I usually don't talk about the economy, but this time I am very worried

1. Look at India's IIP numbers
2. There is a liquidity crunch (banks are not even lending to each other)
3. Unlike last time, we are in a state where need a huge financial bail out

My brother sent an interesting SMS, which read something like

If my bank returns my cheque quoting "Lack of Funds" as the reason. I won't know if the funds were lacking in my account or in the bank

I do believe in the principle that "Money is hardly ever destroyed", why do I say that?

Wealth is usually created, as we find new resources, work harder, make new products or provide new services
In general money passes hands and is never destroyed
Wealth is sometimes destroyed, when we are hit by natural disasters that cause a loss in property, for example

Assuming that my principle holds, in the sub-prime crisis who made money? Where did the money change hands? Did the rich get richer and the poor get poorer? Did we boost our living standard to a higher standard than should have been?

In retrospective from the 2001 recession, web based commerce emerged back stronger and better. The technology, the pricing and the users matured (there were no more freebies for just signing up, BTW, I missed out on all of those :( ). What can expect to see as we come out of this recession? Will banks and insurance, investment companies be smarter? Will there be new regulations to make sure we don't hit such a crisis again?

Looking at the stock market, this is the third slump I've seen and been bitten by, the other two were

Harshad Mehta's stock scam (I was very small/young then, but I understood what was going on)
2001 recession

History has taught me to be optimistic and know that we will come out of the bad times, the only thing to do is be patient, be positive and know that these things take a long time to recover, but they eventually do (or else we are doomed anyway, so what choice do I have, but to be optimistic :) ). Such times, test survival and like nature will choose the fittest to survive and learn from the mistakes of those who didn't survive the recession.

It is a cycle and we've hit the negative part of the cycle, the positives should be around somewhere, I hope we turn around quickly. Let's hope and pray that we quickly recover back from this situation and become stronger.

kernel summit 2008 photo on LWN.net

2008-09-23T10:18:00.003+05:30

For those who have not seen it yet, it is at http://lwn.net/images/conf/lpc-ks-2008/ks-group.jpg

A thumbnail from LWN.net is included below. There were other photographers hired by Linux Foundation, waiting for them to post their photos and compare :)

Why I have not blogged in a while

2008-09-06T00:26:00.002+05:30

Work and family life have kept me occupied. I just returned from OLS in July and I am currently at the airport lounge waiting to board my flight to Portland to attend the Kernel Summit. After the kernel summit, I go on to attend Plumbers Conference. I expect both events to be very exciting and it is a great opportunity for me to catch up with old friends around Portland.

I am not carrying a camera this time around, I intend to buy a good cheap camera, that can obsolete itself without making me worry about spending too much money on it. Conferences are usually a great time to get a lot of work done, lets see what this trip does to my productivity :)

Quote of the day

2008-07-14T19:20:00.001+05:30

"Genius may have its limitations, but stupidity is not thus handicapped"

Elbert Hubbard

Fedora 9 and packaging

2008-05-27T19:01:00.002+05:30

I ran into a weird issue with Fedora 9 today. Just before leaving home, I shut my laptop lid and headed out. In my auto rickshaw on Bangalore roads, I found my bag heating up. To my surprise, I found that the laptop failed to suspend. When I tried again, I saw a popup that said

Hibernate request refused, the package manager prevented the hibernate operation since it was in the middle on an uninterruptible operation or something similar. I had to manually kill all the packagekit processes and yum before I got the laptop to resume.

I should start filing the BUGS I find into bugzilla soon.

Upgraded to Fedora 9

2008-05-16T10:56:00.002+05:30

I eventually took the plunge, upgraded to Fedora 9, the day it was released. What makes my desktop very interesting is that I have an "Nvidia" video card. I upgraded from Fedora Core 8 to Fedora 9. Notice the word core is gone in 9, that's because the core and extras repositories were merged in this release.

I often ask myself, why did I upgrade so quickly - as an after thought. The answer is that I like to try new stuff, I am excited by change, new features, the possibility of getting something better quickly. I think that's the open source philosophy as well "Release early, Release often"

The new features do come at a cost though. I had to spend a few hours trying to bring up my X. Nvidia is not supported as an in kernel driver, there is a proprietary driver for it. Here's what I tried

I used the VESA driver, but I was not happy about the missing graphics acceleration and open GL support
I tried the nvdia driver from livna, but that had other problems - including complaints about ABI not matching. I tried the trick of starting X with -ignoreABI and setting the option in xorg.conf
I wanted to try the driver directly from nvidia, but the kernel compile failed. I got patches from nvidia for 2.6.25 and ran into the same ABI issue. Ignoring ABI was not an option, since the shared library module for the nvidia driver uses a symbol that is now missing with the new X that comes bundled with Fedora 9

Disappointed, I went back to step 1 and I'll wait for the solution to come by or take a shot at a good solution myself. Downgrading X is not a good option, so I am going to hold on to that thought.

While configuring the X server, I remembered my first X install (Slackware, around 1999 or 2000). It came with a utility called xf86config, that asked a set of questions and generated a XFree86 configuration file, with a warning that getting the vertical and horizontal frequencies incorrect could fry the video card. Life is much better with Fedora 9, but not all that easy.

Although, I am beginning to like Fedora better than Ubuntu, Fedora's GUI package management sucks. Yumex is the closest thing it has for sane package management, the gnome based pirut, pacakgeit, etc all leave a user wondering what is going on in the background. I would highly recommend installing yumex and using it as the package manager

Fedora 9 comes with a bunch of kernel features - cgroups, cpu controller, cpu accounting controller and the namespace controller. I had a hand in some of these controllers, but unfortunately the memory controller has been disabled.

Fedora 9 comes bundled with FireFox 3 beta 5 (same as Ubuntu Hardy), FireFox 3 seems pretty cool in terms of user friendliness and stability. Downloading updates can be quite painful, unless you happen to know a very good and fast mirror. Most of the times I've tried to download updates, I get an error stating that the mirror is down or "no such file or directory" or "too many users". I guess that is expected since the whole Linux world is trying to get their hands on Fedora 9.

I found printing to be friendlier and more intuitive. I got errors correctly, stating that my printer was running low on ink or there was a paper jam. The print UI seemed quite robust and stable.

I tried KDE4, only to be a little disappointed. KDE4 on Fedora 9 is definitely much better than it is on kubuntu. Settings are well integrated and one has control over KDE4, unlike kubuntu where the controls are still for KDE3. The reason, I was disppointed with KDE was the interactiveness and latency in terms of response. The new UI is flashy, but most of my widgets failed to work (the comic widget and the dictionary widget, for example). The rendering of gtk based applications is quite poor. Most GUI on Linux seems to use the gtk widget library and some use Qt4. Firefox, eclipse, emacs, etc do not look very nice under KDE. These are still early days for KDE4, I hope it will mature soon into something I would want to use.

OpenOffice 2.4 was pleasantly surprising. As always, they seemed to have improved integration with documents and the generated pdf's look really nice. Usability is much nicer and so is the rendering and interactiveness. I would like to give them a thumbs up for this release. The major difference I saw with respect to Ubuntu's Hardy release was that there was no Sun Logo embedded in the splash screen of OpenOffice. I need to see why Hardy has the Sun Logo embedded.

I am glad to see (this was some time back as well) that Adobe and Google now have Fedora yum repositories, which is a very good sign. I wish nvidia would provide similar repositories.

I've just started using Fedora 9, I'll blog more on it, as I experiment and play with it.

Knuth's recent interview

2008-04-27T09:21:00.002+05:30

Andrew Binstock recently interviewed Knuth. I would highly recommend reading the interview. It was really sad to find out that Knuth has been diagnosed with Prostate Cancer, but here are some my favourite quotations from the interview

"The success of open source code is perhaps the only thing in the computer field that hasn’t surprised me during the past several decades. But it still hasn’t reached its full potential; I believe that open-source programs will begin to be completely dominant as the economy moves more and more from products towards services, and as more and more volunteers arise to improve the code

For example, open-source code can produce thousands of binaries, tuned perfectly to the configurations of individual users, whereas commercial software usually will exist in only a few versions. A generic binary executable file must include things like inefficient "sync" instructions that are totally inappropriate for many installations; such wastage goes away when the source code is highly configurable. This should be a huge win for open source.

Yet I think that a few programs, such as Adobe Photoshop, will always be superior to competitors like the Gimp—for some reason, I really don’t know why! I’m quite willing to pay good money for really good software, if I believe that it has been produced by the best programmers."

"I might as well flame a bit about my personal unhappiness with the current trend toward multicore architecture. To me, it looks more or less like the hardware designers have run out of ideas, and that they’re trying to pass the blame for the future demise of Moore’s Law to the software writers by giving us machines that work faster only on a few key benchmarks! I won’t be surprised at all if the whole multithreading idea turns out to be a flop, worse than the "Titanium" approach that was supposed to be so terrific—until it turned out that the wished-for compilers were basically impossible to write."

"The machine I use today has dual processors. I get to use them both only when I’m running two independent jobs at the same time; that’s nice, but it happens only a few minutes every week. If I had four processors, or eight, or more, I still wouldn’t be any better off, considering the kind of work I do—even though I’m using my computer almost every day during most of the day.

So why should I be so happy about the future that hardware vendors promise? They think a magic bullet will come along to make multicores speed up my kind of work; I think it’s a pipe dream. (No—that’s the wrong metaphor! "Pipelines" actually work for me, but threads don’t. Maybe the word I want is "bubble.") From the opposite point of view, I do grant that web browsing probably will get better with multicores"

"On a positive note, I’ve been pleased to discover that the conventions of CWEB are already standard equipment within preinstalled software such as Makefiles, when I get off-the-shelf Linux these days."

"I currently use Ubuntu Linux, on a standalone laptop—it has no Internet connection. I occasionally carry flash memory drives between this machine and the Macs that I use for network surfing and graphics; but I trust my family jewels only to Linux. Incidentally, with Linux I much prefer the keyboard focus that I can get with classic FVWM to the GNOME and KDE environments that other people seem to like better. To each his own."

"let me just say that almost everything I’ve ever heard associated with the term "extreme programming" sounds like exactly the wrong way to go...with one exception. The exception is the idea of working in teams and reading each other’s code. That idea is crucial, and it might even mask out all the terrible aspects of extreme programming that alarm me."

"I also must confess to a strong bias against the fashion for reusable code. To me, "re-editable code" is much, much better than an untouchable black box or toolkit. I could go on and on about this. If you’re totally convinced that reusable code is wonderful, I probably won’t be able to sway you anyway, but you’ll never convince me that reusable code isn’t mostly a menace."

Atomic access

2008-04-12T20:32:00.004+05:30

I was involved in a set of emails exchanged about per CPU data and atomic access. The argument was basically this

"If you access 64 bit data on a 32 bit machine, what part of the access is atomic?". One would assume that with per-CPU data, it is safe to read the data from a different CPU". The answer lies hidden in the processor architecture. Several RISC architectures require certain types of data to be aligned to specific boundaries (this in turn ensures that the access is atomic). Usually processor manuals suggest that data that is contained within a single cache line is likely to be fetched atomically. Ideally, it is recommended that the data be aligned to the boundary of it's size, so that access is atomic. To explain that further

16 bit data be aligned to a 16 bit boundary
32 bit data be aligned to a 32 bit boundary
64 bit data be aligned to a 64 bit boundary

So the next time you think of atomic access, data sizes, per CPU data, look at your processor manual and determine if the data needs to be protected when accessed from a different CPU.

RSS feed is fixed

2008-04-02T22:34:00.001+05:30

The RSS feed has been changed to export full content instead of the earlier partial content. The blog should be easier and more fun to read with an RSS reader now.

Feeling left out of the software world

2008-04-02T21:06:00.002+05:30

It seems to me that there is a hard barrier between the software development world and the systems programming world. I feel left out of the developments in software that have taken the world over. Agile/Lean programming, EJB, J2EE, .NET, .NET Remoting, JSP, JSTL, Web containers, EJB, MVC, Spring, OpenID, SSO, Indigo, WCF, WPF, Aspect Oriented Programming, Web services, CSS, XML, XSLT, XQuery, ADO, LINQ, AJAX, RSS, RDF, etc. are keywords I hear everyday from my other friends everyday and wonder where I've been while the world has been changing so dramatically?

In retrospect, I've been working on concepts that were quite well understood in the 60's and 70's - Virtualization, Resource Management, Processes, Threads, etc. Concurrency is very interesting, specially due to multi-core now being ubiquitous. My TODO list looks very dull - Python, Algorithms, Architecture of so and so processor, etc.

It seems like there is a hard barrier that prevents people stuck in systems from working in the layer above. I feel left and cut-out from the innovation in the application space. While, I am still finishing up on the basic design patterns, the world has already moved on to domain specific patterns. I do feel lost, but there is hope. Hope that someday, I'll take a look on the other side, where the grass seems greener; jump the fence; make sense of the new world; the world that seems to be moving at a rapid pace.

Doing my time outside of systems programming

2008-03-19T17:58:00.002+05:30

I spend a lot of time doing systems programming. As humbly as possible I don't claim to be an expert at it. While there is a lot of learning to be done on the systems side, the applications side also drags me to it. I feel I should do my time with them, it's their fair due that I owe them; to understand them better and to appreciate them.

I've just started reading Web Services Essentials. I finished chapter 1, it seemed quite well written and was easily understandable. Unfortunately, the websites listed in the book are no longer accessible. That is quite understandable given that the book was written in 2002.

The other favourite book these days is "C# Precisely". It's a well written compact book. The book consists of 30 sections and you get the feeling that you are learning C# with the least possible time investment. I look forward to putting Mono through the C# precisely test

There are also some other things on my plate that I hope to finish up quickly. I suspect that going through this exercise will give me more debating power to argue for/against technology with my friends and colleagues and also help me appreciate what lies on the other side.

Ups and Downs from India's Australian Cricket Tour

2008-03-15T08:51:00.002+05:30

An Indian Fan's view of the ups and downs

Up

India did well without their seniors in the ODIs
Tendulkar helped India win two finals
Dhoni led from the front
Harbhajan Singh managed to dodge charges leveled against him without evidence
India let Brag Hogg go, even though he used abusive words against the Indian captain
Bad umpiring was penalized. Steve Bucknor got his well deserved punishment for bad umpiring (long due, he seemed biased against India)
Hayden was reprimanded for denigrating an Indian player
Australian public criticized the spirit of the Australian Cricket team for unfair play

Down

Adam Gilchrist, a well respected cricketer retired
Michael Clarke got away, even though he tackled Tendulkar in the finals
Symonds seemed out of form
Ricky Ponting seemed out of form
Australian players got away by claiming catches that they really failed to hold on to
Australian media for looking foolish after every charge they leveled against the Indian team players were waved off

Linux 2.6.25-rc1 (new features)

2008-02-14T10:04:00.003+05:30

I am extremely glad to see 2.6.25-rc1, specially due to some of the new features that I've added.

A list of features is mentioned in the LWN article about the merge window for 2.6.25-rc1. This includes the memory controller (now called memory resource controller). Check out http://lwn.net/Articles/268937/ as well. We also got fake NUMA nodes for PowerPC and many other small fixes.

I have a new favorite website for git changelogs http://tree.celinuxforum.org/gitstat/index.php

Check out some of the cool graphs from that website

Linux.conf.au (presentations available)

2008-02-04T12:22:00.000+05:30

Check out http://linux.conf.au/programme/presentations

They also have the talks in .spx format, wonderful!

Bhaskara's proof of the pythagoras's theorem

2008-02-03T10:35:00.000+05:30

Bhaskara's Proof

Bhaskara's proof (1114 AD) of the theorem follows from the figure

So simple, elegant and beautiful. I wish I was aware of this proof as a student

Favourite Quote for the Day

2008-01-09T12:57:00.000+05:30

Loosely speaking we can think of automata, grammar and computability as the study of what can be done by computers in principle, while complexity addresses what can be done in practice.

Peter Linz

Crazy mathematics

2008-01-07T20:02:00.000+05:30

As I was shifting my books from one location to another, I found a big heap of books, I had not even started reading or looked at in detail. Being me, I got distracted by them and decided to at-least give them a chance to fulfill their destiny (to be read cover to cover by their owners or the friends of the owners).

I started with Tom Apostol's Mathematical Analysis. It is a wonderfully terse book and I found myself struggling by the time I reached the topic on "Point Set Topology". I had been through a quick journey of the past - real and complex numbers, sets and cardinality, prime numbers and many more things.

I also ran into the famous Cauchy-Schwarz inequality. I remember having proved the inequality in the exercise of Don Knuth's Art of computer programming volume I, but by now I had forgotten it all -- the sum manipulation, the whole of chapter 1 as hiding somewhere in my memory and seeking it was a hard/impossible task. This time, I found myself taking the help of a symbolic computation package - maxima. My dialog was as follows

(%i2) expand((a1^2 + a2^2)*(b1^2 + b2^2));
(%o2) a2^2*b2^2+a1^2*b2^2+a2^2*b1^2+a1^2*b1^2
(%i4) expand((a1b1 + a2b2)^2);
(%o4) a2b2^2+2*a1b1*a2b2+a1b1^2

(%i31) (a1^2 + a2^2)*(b1^2 + b2^2) - ((a1b1 + a2b2)^2);
(%o31) (a2^2+a1^2)*(b2^2+b1^2)-(a2b2+a1b1)^2
(%i32) expand(%);
(%o32) a2^2*b2^2+a1^2*b2^2+a2^2*b1^2+a1^2*b1^2-a2b2^2-2*a1b1*a2b2-a1b1^2

To cut the long output short, I ended up with Lagrange's inequality.

This is just a small part of the mathematics I have to (re)learn, there is also graph theory, game theory, probability theory, Markov chains and theory of computation.

All the mathematics is very exciting, but time consuming. I have loads of other information to read and digest. Let's see where all this I need to learn this crazy math attitude takes me.

Have a fantastic new year 2008

2008-01-01T09:28:00.000+05:30

It's that time again, a year has gone by, brought happiness and sad moments, but it's gone! Remember to change the year in your dates, make new year resolutions, start afresh, be more positive, thankful and happy that we have a new chance to do/make things right.

HAVE A GREAT NEW YEAR and make every day count

Rusting Knowledge

2007-12-29T19:14:00.000+05:30

Over a period of time, it seems like a layer of dust covers your deep understanding and knowledge of a subject matter, where in once I was considered an expert. My knowledge is rusting and it's time to re-read some old classics and books I used to learn the subject matter from.

I've been trying to learn C#, Python, etc, but I realize that I need to revisit my C skills and my C99 knowledge base again. In summary, knowledge rusts over a period of time, specially the items not practiced very often.

Get ready to clear away the dust from your rusting areas as well, as I explore well known areas and newer areas with a "I used to know, but forgot" perspective.

Digging out of history (longjmp is bad)

2007-12-24T04:14:00.000+05:30

I had this program written out a long time back, it shows why some constructs are valid, but do not apply well today. In the evolution of C++, we've left behind some holes

1 #include <stdio.h>
2 #include <setjmp.h>
3 #include <string.h>
4
5 class C {
6 private:
7         char *ptr;
8 public:
9         C (const char *name) {
10                 ptr = new char[strlen(name)+1];
11                 printf("constructed C\n");
12         }
13
14         ~C () {
15                 delete [] ptr;
16                 printf("destroyed C\n");
17         }
18 };
19
20 void funfunction(jmp_buf env)
21 {
22         C c("Hello");
23         /*
24          * Do something, at the end expect destructor to be
25          * called
26          */
27         longjmp(env, 1);
28 }
29
30 int main(void)
31 {
32         jmp_buf env;
33         int ret;
34
35         ret = setjmp(env);
36         if (ret) {
37                 printf("Looks like we jumped a long way\n");
38                 return ret;
39         }
40
41         funfunction(env);
42         return 0;
43 }

See if you can find the obvious problem with this code

Sounds in my life

2007-12-22T11:53:00.000+05:30

The gentle and shrill sounds in my everyday life, call my attention to them. In earlier days, the only sound that one would hear is of people talking to them, children playing on the street or a baby calling for Mama's attention.

Compare and contrast that with what we hear today; the sound of the TV, the microwave, radio, music player, sound of vehicles zooming on the street, vehicles blowing horns, the telephone, the cell phone trying to tell you someone wants to talk to you (even when you are in the restroom), this someone could be a pre-recorded sales call; the computer buzzing to tell you that someone is trying to reach you through instant chat, the courier person ringing the doorbell, the alarm-clock ringing on my cell phone

How am I supposed to listen to myself and others around me; with these distracting sounds calling for my attention. We have moved into a new era, where we need more sounds to tell us, that we are needed elsewhere. I need to filter these sounds, so that I can hear my heart-beat, the pin-drop and my those around me giggle and laugh.

Guess what OS Don Knuth runs?

2007-11-22T10:21:00.000+05:30

Check out http://www-cs-faculty.stanford.edu/~knuth/news.html

In the section "Wanted: A Name For High-Tech Grief" Knuth states and I quote

"I myself have often cried out for help to colleagues who have generously made house calls, in order to unwedge my highly customized Linux system"

We've known it for a while, looking at the customized fvwm2 configuration on Knuth's website, but it's good to see it in writing.

Some of you must be thinking, he has problems with Linux? We'll look at the keywords -- highly customized. Can't do that with other operating systems without hitting yourself in the head a few times or hitting your head against something. You don't hit yourself because your stupid, you do, because you brought the product :-)

Hmmm.... Now, if we can get everyone who has directly or in-directly been benefited from Knuth's work to run Linux, that would be a wonderful starting place. Of-course regular users are more than welcome to adopt and customize Linux.

Linux is a Trademark of Linus Torvalds

FOSS.IN delegate registration is open

2007-11-06T17:23:00.000+05:30

Register at http://foss.in/2007/register/delegates/

The fee structure has changed this year. Do read the details before registering. This year we have project days and the main conference

Talk at VTU

2007-11-03T07:13:00.000+05:30

I gave a talk on Introduction to Operating Systems via EDUSAT. The lecture was broadcast to several universities via satellite. I had no live audience, but it was fun to speak into a camera. The video has been stored/archived for students to see later.
Here's a link to the slides

New Code in the Linux Kernel

2007-11-03T06:51:00.000+05:30

I got some new code included into the mainline linux 2.6.24-rc1 kernel

cgroupstats - Is an infrastructure to allow sending control group statistics to user space using taskstats/genetlink
cpu_acct - CPU accounting subsystem for control groups

Worked on some other miscellaneous stuff as well. Overall, 2.6.24 was an interesting merge cycle, lots of new stuff went it. Check it out! Please do report regressions

A Quick Estimate

2007-11-03T00:45:00.000+05:30

I was trying to estimate how long it would take for a timer, measured in nano-seconds using 64 bits would take to roll over. Here's my quick estimate

It would take 2^64/10^9 seconds = 2^64/2^9*5^9

Approximating on all calculations

= 2^55/5^9

5^3 = 125 ~= 2^7
5^9 = 2^21

= 2^55/2^21

= 2^34 seconds

2^34 seconds = 2^34/86500 days ~= 2^34/80*2^10 = 2^24/2^6 days = 2^18 days

1 year = 365 days, 3 years ~= 2^10 days

That leaves us with 2^8 years * 3 years

= 256*3 years before the timer overflows

With a machine, usually one would expect at-least one reboot in 800 years, if so, we would be fine for a long time to come.

See I need no calculator :-)

FOSS.IN list of talks announced

2007-10-27T18:24:00.000+05:30

Check out http://foss.in/2007/shortlist.php

The list of talks looks really good and I know a lot of people presenting at FOSS.IN. I am co-presenting on one topic. I'd say this year FOSS.IN is going to rock, so make sure your there.

India vs Australia (quick analysis)

2007-10-08T18:43:00.000+05:30

India won the T20 world cup and became champions! The 50-50 games seem to be a different playing ground for the Indian Team. Have you been wondering why India did not fair so well, so far. Here's a quick layman analysis

India have not been batting first, in all the T20 matches we won, we batted first!
The team has changed and so have the rules. Instead of a powerplay for 20 overs with catch in fielders around, T20 has restrictions for just 4 overs. This makes a big difference to players like Sehwag and Gambhir, who I think are more suited to the field being well spread out (survive longer)

Here's some advice for the Indian Team (given that Dhoni reads cricinfo, you never know if he might read this blog as well :-) )

Convert the 50-50 match to a 20-20 match, by keeping wickets in hand till the 30th over
While batting second, get Dhoni in at #3, followed by Yuvraj at #4
Get Dravid to Open the batting while chasing
Tendulkar should come 4/5 down while chasing (when there is a mandatory ball change)
Don't ever get Yuvraj to Bowl :-)
While bowling first, attack aggressively, even if it means that more runs will be conceded

Memory Ordering (Recommended Reading)

2007-10-05T22:46:00.000+05:30

I just finished reading this wonderful report on memory ordering. I highly recommend reading it. If you have anything to do with multi-core, multi-processor, parallel programming, you'll find the paper very insightful.

Other good to read papers/articles on memory ordering from Paul Mckenney are

C++ Data-Dependency Ordering. May 2007.
Overview of Linux-Kernel Reference Counting. January 2007.
A simple and efficient memory model for weakly ordered architectures. Makes case for weakly ordered primitives in programming languages. Updated May 2007.

Doing the simple things first

2007-09-26T00:32:00.000+05:30

I've always been lost trying to understand and do the complex things. I just realized that I miss out on doing and enjoying the simple things in life. Note to self, remember this and change.

India are Twenty20 champs

2007-09-25T00:26:00.000+05:30

No one expected it, but secretly hoped for it; and it has happened. India are twenty 20 world cup champions. Boy, has this been a good time for sports. For those of you who do indeed know that hockey is our national game, spare a moment for this picture as well

Spare some time and visit http://www.bharatiyahockey.org/ and http://www.indianhockey.com/.

Now shifting back to twenty20, India beat Pakistan twice and the second win won us the cup. Both matches were close, nail biting (warning: watch your hygiene) finishes. Surprisingly, India got extremely lucky and batted first in almost all their encounters which they won. The statistics show a remarkable quality, that has been missing before, this was a true team effort. Everybody chipped in; in the batting department, we had contributions from Gautham Gambhir, Virendra Sehwag, Robin Uttapa, Yuvraj Singh, M. S. Dhoni, Rohit Sharma (who incidentally is yet to be dismissed in this form of the game). Karthik was a weak spot in the team, but boy did he keep well in the game against South Africa. In the bowling department, R. P. Singh, Irfan Pathan, Harbhajan Singh and Sreesanth were the key contributors.

India's fielding has been quite good, thanks to the absence of Saurav Ganguly, V.V.S. Laxman and Munaf Patel.

I am sure Dhoni is thinking मै तो युहीं चाला था बिना जाने मंज़िल मगर लोग आते गये और कारवाँ बंता गया |

Well done, keep up the good work boys!

Containers update - more photos

2007-09-11T22:58:00.000+05:30

The containers team - catching up in Cambridge

There is a containers update at http://community.livejournal.com/openvz/17964.html

More interesting math

2007-09-11T14:15:00.000+05:30

I came across the The Encyclopedia of Integer Sequences and the really interesting web site on Mathematical Constants. I am currently reading A Passion for Mathematics by Clifford A. Pickover .

Ramanujan's work online

2007-09-11T13:46:00.000+05:30

I found this interesting website containing works of Ramanujan.

Knuth finally sells out

2007-09-11T12:54:00.001+05:30

Really funny, I ran into it today.

Kernel summit 2007 group photo

2007-09-09T08:31:00.000+05:30

Posted at LWN.net