| Andrew Cooke | Contents | Latest | RSS | Twitter | Previous | Next

C[omp]ute

Welcome to my blog, which was once a mailing list of the same name and is still generated by mail. Please reply via the "comment" links.

Always interested in offers/projects/new ideas. Eclectic experience in fields like: numerical computing; Python web; Java enterprise; functional languages; GPGPU; SQL databases; etc. Based in Santiago, Chile; telecommute worldwide. CV; email.

Personal Projects

Lepl parser for Python.

Colorless Green.

Photography around Santiago.

SVG experiment.

Professional Portfolio

Calibration of seismometers.

Data access via web services.

Cache rewrite.

Extending OpenSSH.

C-ORM: docs, API.

Last 100 entries

UNUMS (Universal Number Format); MOOCs (Massive Open Online Courses); Interesting Looking Game; Euler's Theorem for Polynomials; Weeks 3-6; Reddit Comment; Differential Cryptanalysis For Dummies; Japanese Graphic Design; Books To Be Re-Read; And Today I Learned Bugs Need Clear Examples; Factoring a 67 bit prime in your head; Islamic Geometric Art; Useful Julia Backtraces from Tasks; Nothing, however, is lost with less discomfort than that which, when lost, cannot be missed; Article on Didion; Cost of Living by City; British Slavery; Derrida on Metaphor; African SciFi; Traits in Julia; Alternative Japanese Lit; Pulic Key as Address (Snow); Why Information Grows; The Blindness Of The Chilean Elite; Some Victoriagate Links; This Is Why I Left StackOverflow; New TLS Implementation; Maths for Physicists; How I Am 8; 1000 Word Philosophy; Cyberpunk Reading List; Detailed Discussion of Message Dispatch in ParserCombinator Library for Julia; FizzBuzz in Julia w Dependent Types; kokko - Design Shop in Osaka; Summary of Greece, Currently; LLVM and GPUs; See Also; Schoolgirl Groyps (Maths); Japanese Lit; Another Example - Modular Arithmetic; Music from United; Python 2 and 3 compatible alternative.; Read Agatha Christie for the Plot; A Constructive Look at TempleOS; Music Thread w Many Recommendations; Fixed Version; A Useful Julia Macro To Define Equality And Hash; k3b cdrom access, OpenSuse 13.1; Week 2; From outside, the UK looks less than stellar; Huge Fonts in VirtualBox; Keen - Complex Emergencies; The Fallen of World War II; Some Spanish Fiction; Calling C From Fortran 95; Bjork DJ Set; Z3 Example With Python; Week 1; Useful Guide To Starting With IJulia; UK Election + Media; Review: Reinventing Organizations; Inline Assembly With Julia / LLVM; Against the definition of types; Dumb Crypto Paper; The Search For Quasi-Periodicity...; Is There An Alternative To Processing?; CARDIAC (CARDboard Illustrative Aid to Computation); The Bolivian Case Against Chile At The Hague; Clear, Cogent Economic Arguments For Immigration; A Program To Say If I Am Working; Decent Cards For Ill People; New Photo; Luksic And Barrick Gold; President Bachelet's Speech; Baltimore Primer; libxml2 Parsing Stream; configure.ac Recipe For Library Path; The Davalos Affair For Idiots; Not The Onion: Google Fireside Chat w Kissinger; Bicycle Wheels, Inertia, and Energy; Another Tax Fraud; Google's Borg; A Verion That Redirects To Local HTTP Server; Spanish Accents For Idiots; Aluminium Cans; Advice on Spray Painting; Female View of Online Chat From a Male; UX Reading List; S4 Subgroups - Geometric Interpretation; Fucking Email; The SQM Affair For Idiots; Using Kolmogorov Complexity; Oblique Strategies in bash; Curses Tools; Markov Chain Monte Carlo Without all the Bullshit; Email Para Matias Godoy Mercado; The Penta Affair For Idiots; Example Code To Create numpy Array in C; Good Article on Bias in Graphic Design (NYTimes); Do You Backup github?; Data Mining Books

© 2006-2015 Andrew Cooke (site) / post authors (content).

Matlab on NVidia GPUs

From: andrew cooke <andrew@...>

Date: Sat, 17 Oct 2009 07:35:17 -0300

I can't find any notes of what used to exist, but there are now 2
companies - one appears to be offering freeware (but not yet on
Linux).

http://gp-you.org/index.php (free)

http://www.accelereyes.com/ (commercial)

Andrew

Calling OpenCL Directly

From: andrew cooke <andrew@...>

Date: Mon, 28 Dec 2009 21:21:53 -0300

Instead of using those libraries, I ended up writing OpenCL (which is
very similar to CUDA, but cross-platform) directly.  The final speedup
was a factor of 100.

The reason I didn't use the libraries is that I couldn't see how they
could work efficiently for our case.  There were two reasons for this.

First, I tried vectorizing the Matlab code so that it might use
multiple cores on the CPU.  This was a failure, which made me suspect
that the code didn't have the form necessary to be auto-parallelized
(in the very core of the loop is an indirection which makes things
non-trivial).

Second, I was dealing with large data sets and needed to have qute
detailed control over what data was moved onto the GPU at what time
(again related to the indirection).

The entire project (including rewriting code in plain C as well as in
OpenCL) was 1-2 months, and got a 100x speedup.  An awful lot of that
time was spent (1) reverse engineering the algorithm I was porting and
(2) learning the details of OpenCL/CUDA.  Knowing what I know now, I
could repeat the work in a week.

The 100x speedup sounds impressive, but plain C was 6x faster than
Matlab, so the GPU only adds another factor of 17.  This is, I think,
because of the indirection I discussed earlier - the memory accesses
cannot be coallesced, which makes the entire calculation memory bound
(although I have not yet profiled the app to check this).

On the other hand, the original code was running on a rather
expensive, new dual Xeon box.  The GPU was a sub-$200 generic card
from newegg.  So "speed per $" is over x1000....

Andrew

Matlab/OpenCL Cross Reference

From: andrew cooke <andrew@...>

Date: Mon, 28 Dec 2009 21:22:43 -0300

PS See http://www.acooke.org/cute/Experience0.html

Comment on this post