Re: [ublas] thread safety of matrix multiplication

Subject: Re: [ublas] thread safety of matrix multiplication
From: Gunter Winkler (guwi17_at_[hidden])
Date: 2009-11-25 15:36:28

Am Wednesday 25 November 2009 schrieb James C. Sutherland:
> If I have a ublas matrix object, is it thread safe w.r.t. matvec
> operations?  In other words:
>
> typedef boost::numeric::ublas::compressed_matrix< double,
> boost::numeric::ublas::row_major > MatType;
>
> MatType mat;  // both threads use the same matrix object.
> VecType a1, b1, a2, b2;
>
> // ... assemble matrix and vectors ...
> //  ...
>
> // thread 1 code:
> axpy_prod( mat, a1, b1, true );
>
> // thread2 code:
> axpy_prod( mat, a2, b2, true );
>
> Should this be thread safe?  My observation is that it is NOT.  I am
> getting memory corruption somewhere.  

This is quite strange because axpy_prod only reads from the matrix and 
a1. The only write access is to b1. Can you try to build a small test 
program that shows the memory corruption?

> Also, it seems that axpy_prod is no longer included in the boost
> documentation (html) - is that function being deprecated in favor of
> the prod(...) functions?

axpy_prod is mentioned here: 
http://www.boost.org/doc/libs/1_41_0/libs/numeric/ublas/doc/operations_overview.htm#32products

However I agree, that the operations.hpp needs more documentation. 

mfg
Gunter