[petsc-users] Some papers for additive schwarz and blocked jacobi?

Jed Brown jed at 59A2.org
Mon Jun 6 10:22:55 CDT 2011

2011/6/6 Dürrwang, Jürgen <Juergen.Duerrwang at iosb.fraunhofer.de>

> 1.Load Matrix which should be solve to CPU and GPU
> 2.Decompose in blocks, so on each block an ILU(0) can run in
> “parallel”.              : CPU
> 3.Loop until tolerance is reached
> 4.Solve each block in parallel to get an preconditioner
>                                                : CPU
> 5.Solve CG with preconditioner to break down iteration number
>                 :GPU

Step 5 is not all on the GPU. You do a matrix multiple and a dot product on
the GPU, then move the vector over to the CPU, put the pieces on different
cores, solve, put it back on the GPU.

> 6.End loop
> There are about 4 copies between CPU /GPU per step, but that isn’t a
> problem

You have a copy each way *per CG iteration*. I think it is a problem.
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