[ViennaCL-devel] Computing A += prod(B,C)

[Philippe T. <phi...@gm...>]

Hello everybody !

I'll inaugurate this mailing list with a little question.
I have not seen any kernel for computing the operation A += prod(B,C) .
Does this mean that this operation is done doing :

tmp = prod(B,C)
a+=tmp

?

For computing the multi_matrix ( project i'm working on, matrix composed of
multiple handles, to solve the CL_MAX_ALLOCABLE_MEMORY and the multi
devices issue), I need to do several updates of this kind, in a block
layout. For a 2*2 block layout :

C(0,0).clear();
=>
C(0,0) += prod( A(0,0), B(0,0) )
=>
C(0,0) += prod( A(0,1), B(1,0) )

C(0,1).clear();
=>
C(0,1) += prod( A(0,0), B(0,1) )
=>
C(0,1) += prod( A(0,1), B(1,1) )

...
...

This "sort-of-rank-1-update approach" is a special case of the SUMMA
Algorithm (OpenCL doing the memory transfers in the back ground, for now at
least) and seems to be efficient from a memory point of view. Using another
approach would lead to both a huge memory consumption and significant
memory transfers...

Is there any way of doing so in ViennaCL ?

Best regards !
Phil