graduate hatI just graduated with a Bachelor of Science degree in Physics from the University of Latvia!

It took me 4 years to complete the studies. During these years I took more than 50 courses from physics, mathematics and computer science departments and my average grade was 9.1/10 (students in Latvia are graded from 1 up to 10, 10 being excellent, 9 being very good, ..., 4 being the lowest grade for passing a course. Anything below 4 means failure).

As I already mentioned in the about me page, I chose to study physics because I already had a broad understanding of various topics of computer science. Now I can proudly say that I understand a lot of physics as well.

Here is a picture of me with a diploma in my hands. :)

peteris krumins with a diploma at university of latvia

Here is another picture with all of us who graduated from University of Latvia with a B.Sc. degree in Physics in 2008. I'm right in the middle of the front row!

university of latvia physics graduates 2008

Talking about my future plans, I decided not to go to a graduate school just yet. I'll spend the next year or two hacking on whatever interests me the most and learn exactly what I have wanted (more mathematics and more computer science). It also means that I will be able to post more frequently here. :)

Thanks for reading my blog!

This article is part of the article series "Musical Geek Friday."
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richard stallman - gnu free software foundation - the free software songThis week on Musical Geek Friday - The Free Software Song!

The song is written and performed by the founder of Free Software Foundation and the most active free software advocate Richard Stallman (scroll down for a video of Mr. Stallman performing it himself).

Richard wrote this song at a filksinging session at a science fiction convention. He realized he had never written a filksong relating to free software, so he figured it was time he did. He remembered that he had never written a filksong using Bulgarian dance music, so he figured that would be a good thing to do for once. He chose Sadi Moma because it is not too fast or complicated, and is easy to sing.

Here it is - The Free Software Song!

[audio:http://www.catonmat.net/download/richard_stallman-free_software_song.mp3]

Download this song: the free software song.mp3 (musical geek friday #9)
Downloaded: 13673 times

Download lyrics: the free software song lyrics (musical geek friday #9)
Downloaded: 1725 times

Here is the lyrics of The Free Software Song:

Join us now and share the software;
You'll be free, hackers, you'll be free.
Join us now and share the software;
You'll be free, hackers, you'll be free.

Hoarders may get piles of money,
That is true, hackers, that is true.
But they cannot help their neighbors;
That's not good, hackers, that's not good.

When we have enough free software
At our call, hackers, at our call,
We'll throw out those dirty licenses
Ever more, hackers, ever more.

Join us now and share the software;
You'll be free, hackers, you'll be free.
Join us now and share the software;
You'll be free, hackers, you'll be free.

Here is Richard Stallman himself performing The Free Software Song:

The audio quality of this video is poor. Here is a much better version by a band with a hilarious title "The GNU/Stallmans":

Download "The Free Software Song"

Download this song: the free software song.mp3 (musical geek friday #9)
Downloaded: 13673 times

Download lyrics: the free software song lyrics (musical geek friday #9)
Downloaded: 1725 times

Click to listen:
[audio:http://www.catonmat.net/download/richard_stallman-free_software_song.mp3]

Have fun and until next geeky Friday! :)

shmoocon hacker hacking videosHere are more hacker videos (previous post was on Defcon videos). This time they are from Shmoocon hacker conference. They put out videos from 2006, 2007 and they are putting out videos from 2008 pretty soon.

Shmoocon, as they describe themselves, is an annual East coast hacker convention hell-bent on offering three days of an interesting atmosphere for demonstrating technology exploitation, inventive software & hardware solutions, and open discussions of critical infosec issues.

Here are the videos from Shmoocon 2006:

Here are the videos from Shmoocon 2007:

Here are the videos from Shmoocon 2008:

Enjoy and don't forget to comment on which videos you liked the best!

prime number problem of google treasure hunt 2008I just found out about Google's Treasure Hunt 2008. They say that "it's a puzzle contest designed to test yer problem-solving skills in computer science, networking, and low-level UNIX trivia."

Apparently I have missed the first three puzzles (first, second and third) but I'll give the fourth puzzle a shot.

The fourth problem is about prime numbers and it's formulated as following:

Find the smallest number that can be expressed as
the sum of 7 consecutive prime numbers,
the sum of 17 consecutive prime numbers,
the sum of 41 consecutive prime numbers,
the sum of 541 consecutive prime numbers,
and is itself a prime number.

For example, 41 is the smallest prime number that can be expressed as
the sum of 3 consecutive primes (11 + 13 + 17 = 41) and
the sum of 6 consecutive primes (2 + 3 + 5 + 7 + 11 + 13 = 41).

The Solution

I'll write how I got the solution as I go, so I'll mix the past and present tenses in this post. Sometimes I'll write what I am going to do and sometimes I'll write what I just did.

I have no desire to generate lists of prime numbers myself as it has been done infinitely many times already. I'll just use a publicly available list of prime numbers! Here is a list of first fifty million primes.

I'll use my Unix-fu to find the solution.

First I noticed that the primes are zipped and split into chunks of million primes per file. The file names are like "primes1.zip", ... "primes50.zip".

A quick loop from 1 to 50 and wget gets all these files to my hard drive:

$ for i in $(seq 50); do wget "http://primes.utm.edu/lists/small/millions/primes$i.zip"; done

Next, I unzip all these files, and remove those zips to save space:

$ for i in $(seq 50); do unzip "primes$i.zip" && rm -f "primes$i.zip"; done

After doing that and looking at what I got, I realized that they were in some strange format, 8 primes per line, space padded and with some text on the first two lines. Here is an example how the first five lines look in primes1.txt file:

                 The First 1,000,000 Primes (from primes.utm.edu)

         2         3         5         7        11        13        17        19
        23        29        31        37        41        43        47        53
        59        61        67        71        73        79        83        89

I want all my primes to be in one file and one prime per line so I can extract N-th prime by looking at that line.
I used the following command to merge all the files into a single file:

for i in $(seq 50); do (awk 'BEGIN { OFS="\n" } NR > 2 {print $1,$2,$3,$4,$5,$6,$7,$8}' primes$i.txt >> primes.txt) && rm -f primes$i.txt; done

A quick verification that I did not lose any primes:

$ wc -l primes.txt
50000000 primes.txt

Now I'll create four files which contain sums of 7, 17, 41 and 541 consecutive primes, not exceeding the biggest prime in primes.txt file. I did that with the following AWK one-liner:

$ last=$(tail -1 primes.txt)
$ for N in 7 17 41 541
  do
   awk 'BEGIN { prev[0] = 0 } NR < '$N' {prev[NR] = $1; sum += $1 } NR >= '$N' { psum += prev[NR-'$N']; delete prev[NR-'$N']; prev[NR] = $1; sum += $1; if (sum - psum > '$last') { exit } printf "%d\n", sum - psum }' primes.txt > primes$N.txt
  done

The command created primes7.txt, primes17.txt, primes 41.txt and primes541.txt files. These files contain sums of prime numbers and just some of them are primes.

The solution, if it exists in the given data set, is the intersect of all these files. If there are multiple items in the intersect, the smallest should be chosen and checked if it really was a prime.

$ sort -nm primes541.txt primes41.txt | uniq -d | sort -nm primes17.txt - | uniq -d | sort -nm primes7.txt - | uniq -d
7830239
$ grep -m1 7830239 primes.txt
7830239

We have found the solution! It's 7830239!

I submitted the answer and after a few minutes it was confirmed to be correct! Awesome!

Your question: [7, 17, 41, 541]
Your answer: 7830239
Time received: 2008-06-06 23:33:26.268414 UTC

Correct answer: 7830239
Your answer was: Correct

Now leave a comment and tell me how you solved this problem!

This article is part of the article series "Musical Geek Friday."
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the bill gates song, photo from microsoft 1983This week on Musical Geek Friday - The Bill Gates Song!

I found this song while watching a TED Talk on good vs. bad software interfaces called "When It Comes to Tech, Simplicity Sells" (scroll to the bottom to view this talk). To funny things up the speaker, David Pogue, bursted into a few songs, one of them being a song about Bill Gates.

David Pogue is the personal-technology columnist for the New York Times. Each week, he contributes a print column, an online column and an online video. His daily blog, "Pogue's Posts," is the Times's most popular blog.

So, here it is! The Bill Gates Song:

[audio:http://www.catonmat.net/download/david_pogue-bill_gates_song.mp3]

Download this song: the bill gates song.mp3 (musical geek friday #8)
Downloaded: 92762 times

Download lyrics: the bill gates song lyrics (musical geek friday #8)
Downloaded: 3174 times

Here is the lyrics of The Bill Gates Song:

I've been a geek forever,
And I wrote the very first DOS.
I put my software and IBM together,
I got profit, and they got the loss!
I write the code that makes the whole world run,
I'm gettin' royalties from everyone.
Sometimes it's garbage, but the press is snowed,
You buy the box, I sell the code.

Every software company
Is doing Microsoft's R&D.
You can't keep a good idea down these days.
Even Windows is a hack
We kinda based loosely on the Mac.
So it's big, so it's slow,
You've got nowhere to go!
I'm not doing it for praise!

I write the code that fits the world today,
Big mediocrity in every way.
We've entered planet domination mode,
You'll have no choice, you'll buy my code.
I am Bill Gates, and I write the code!

Here is the TED Talk with the song. The talk includes another two songs about Steve Jobs and technical support nightmare.

Direct link: http://www.ted.com/index.php/talks/view/id/7

Download "The Bill Gates Song"

Download this song: the bill gates song.mp3 (musical geek friday #8)
Downloaded: 92762 times

Download lyrics: the bill gates song lyrics (musical geek friday #8)
Downloaded: 3174

Click to listen:
[audio:http://www.catonmat.net/download/david_pogue-bill_gates_song.mp3]

Have fun and until next geeky Friday! :)