Re: [boost] Re: matrix library ?

From: Pierre Aubert (pierre.aubert_at_[hidden])
Date: 2001-03-28 04:56:38

lums_at_[hidden] writes:

> --- In boost_at_y..., boost_at_s... wrote:
> 
> > > 
> > > Yes and No.  It also affects how algorithms are written and at 
> some
> > > extent, their efficiency.
> > > 
> 
> > 
> > actually one should provide both storage formats.
> > Art least I'm confronted with (dense, rather large) matrix 
> > multiplications of the form A_i * B_i, where A_i always appear on 
> > the left, and B_i appears on the right. 
> > So using different storage layouts, I can increase performance
> > since no strides appear.

Using ATLAS or one of the cited sources below, you will increase
performances by a factor of 4 to 5 even on a pentiumII, this factor
increase on better processors of course.

> 
> For dense time dense the storage layout of the original matrices is 
> somewhat irrelevant for performance issues.  By performing 
> appropriate blocking and re-arranging for optimal layout within the 
> working blocks, one can get optimal performance for any original 
> layout.  ATLAS, PhiPAC, optimized BLAS, and MTL all do this AFAIK.

> That is, yes, layout is important, but only in the working blocks.  
> Any original storage format can be copied to a good orientation in 
> the working blocks within the mat-mult algorithm.

-- 
Pierre F. Aubert                          pierre.aubert(at)echo.fr
http://pierre(dot)aubert(dot)free(dot)fr  pierre.aubert(at)free.fr