| 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.

Last 100 entries

Retiring Essentialism; Poorest in UK, Poorest in N Europe; I Want To Be A Redneck!; Reverse Racism; The Lost Art Of Nomography; IBM Data Center (Photo); Interesting Account Of Gamma Hack; The Most Interesting Audiophile In The World; How did the first world war actually end?; Ky - Restaurant Santiago; The Black Dork Lives!; The UN Requires Unaninmous Decisions; LPIR - Steganography in Practice; How I Am 6; Clear Explanation of Verizon / Level 3 / Netflix; Teenage Girls; Formalising NSA Attacks; Switching Brakes (Tektro Hydraulic); Naim NAP 100 (Power Amp); AKG 550 First Impressions; Facebook manipulates emotions (no really); Map Reduce "No Longer Used" At Google; Removing RAID metadata; New Bike (Good Bike Shop, Santiago Chile); Removing APE Tags in Linux; Compiling Python 3.0 With GCC 4.8; Maven is Amazing; Generating Docs from a GitHub Wiki; Modular Shelves; Bash Best Practices; Good Emergency Gasfiter (Santiago, Chile); Readings in Recent Architecture; Roger Casement; Integrated Information Theory (Or Not); Possibly undefined macro AC_ENABLE_SHARED; Update on Charges; Sunburst Visualisation; Spectral Embeddings (Distances -> Coordinates); Introduction to Causality; Filtering To Help Colour-Blindness; ASUS 1015E-DS02 Too; Ready Player One; Writing Clear, Fast Julia Code; List of LatAm Novels; Running (for women); Building a Jenkins Plugin and a Jar (for Command Line use); Headphone Test Recordings; Causal Consistency; The Quest for Randomness; Chat Wars; Real-life Financial Co Without ACID Database...; Flexible Muscle-Based Locomotion for Bipedal Creatures; SQL Performance Explained; The Little Manual of API Design; Multiple Word Sizes; CRC - Next Steps; FizzBuzz; Update on CRCs; Decent Links / Discussion Community; Automated Reasoning About LLVM Optimizations and Undefined Behavior; A Painless Guide To CRC Error Detection Algorithms; Tests in Julia; Dave Eggers: what's so funny about peace, love and Starship?; Cello - High Level C Programming; autoreconf needs tar; Will Self Goes To Heathrow; Top 5 BioInformatics Papers; Vasovagal Response; Good Food in Vina; Chilean Drug Criminals Use Subsitution Cipher; Adrenaline; Stiglitz on the Impact of Technology; Why Not; How I Am 5; Lenovo X240 OpenSuse 13.1; NSA and GCHQ - Psychological Trolls; Finite Fields in Julia (Defining Your Own Number Type); Julian Assange; Starting Qemu on OpenSuse; Noisy GAs/TMs; Venezuela; Reinstalling GRUB with EFI; Instructions For Disabling KDE Indexing; Evolving Speakers; Changing Salt Size in Simple Crypt 3.0.0; Logarithmic Map (Moved); More Info; Words Found in Voynich Manuscript; An Inventory Of 3D Space-Filling Curves; Foxes Using Magnetic Fields To Hunt; 5 Rounds RC5 No Rotation; JP Morgan and Madoff; Ori - Secure, Distributed File System; Physical Unclonable Functions (PUFs); Prejudice on Reddit; Recursion OK; Optimizing Julia Code; Cash Handouts in Brazil; Couple Nice Music Videos; It Also Works!; Adaptive Plaintext

© 2006-2013 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