Re: octave 64-bit and multi-threading

[Dmitri A. Sergatskov]

On Mon, Jul 20, 2015 at 2:37 PM, Grothausmann, Roman Dr. <address@hidden> wrote:

Dear mailing list members,


Using instructions from
https://www.gnu.org/software/octave/doc/interpreter/Compiling-Octave-with-64_002dbit-Indexing.html
I managed to compile octave-4.0.0 with --enable-64 using a 64-bit atlas library under debian.
The test
a = zeros (1024*1024*1024*3, 1, 'int8');
works.
I was also able to load 10GB units with fread and do some computations with it successfully.

According to
http://stackoverflow.com/questions/11889118/get-gnu-octave-to-work-with-a-multicore-processor-multithreading
octave should be multi-threaded when using a self-compiled atlas lib.
However the test

tic
bigMatrixA = rand(3000000,80);
bigMatrixB = rand(80,30);
bigMatrixC = bigMatrixA * bigMatrixB;
toc
disp("done");

takes 4.8s with the debian default octave (3.8.2 32-bit)
and 7.1s with my self-compiled octave (4.0.0 64-bit)

Is it slower because it is now 64-bit?
Are there better test for multi-threading in octave?

​Run top in a separate terminal and see if octave process takes more than 100%.

(while running your test).

Compiling optimized atlas is tricky. For one thing make sure you have disabled
CPU throttling.

 

Thanks for any help or hints
Roman

​Dmitri.
--
​