[concurrency-interest] forkjoin matrix multiply

David J. Biesack David.Biesack at sas.com
Wed Jan 30 13:35:24 EST 2008


> Date: Tue, 29 Jan 2008 16:43:36 -0500
> From: "Tim Peierls" <tim at peierls.net>
> Subject: Re: [concurrency-interest] forkjoin matrix multiply
> 
> On Jan 29, 2008 4:28 PM, Mark Thornton <mthornton at optrak.co.uk> wrote:
> 
> > Joe Bowbeer wrote:
> > > If so, would it be beneficial for us to look inside jama.Matrix, with
> > > the goal of enabling its implementors to parallelize its operations
> > > (using forkjoin tools) in a straightforward manner?
> > >
> > I think high performance matrix multiply is usually done with the matrix
> > divided into tiles or blocks, such that a couple of tiles fit neatly
> > into the processor cache. This technique is applied for each cache level
> > (blocks within blocks ...). While the forkJoin tools can help, I'm not
> > sure how the parallel array mechanisms help here.
> 
> Agreed. I think David's example is mainly about comparing a
> ThreadPoolExecutor design to a ForkJoin design, not just in performance but
> in succinctness. I don't think it was intended as a serious example of doing
> high-performance matrix multiplication.
> 
> --tim

Most definitely. The examples merely show how to take an existing sequential algorithm and apply ForkJoin to it.

Developing more realistic examples can help refine the API as well; Doug is already considering some additions/enhancements spawned by writing this example (IndexedProcedure; ParallelIntRange). Framework design requires lots of use cases; Matrix Multiply is simply a well understood case. 

Please try more examples and add them to the wiki at http://artisans-serverintellect-com.si-eioswww6.com/default.asp?W32

-- 
David J. Biesack     SAS Institute Inc.
(919) 531-7771       SAS Campus Drive
http://www.sas.com   Cary, NC 27513



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