std.parallelism: Request for Review

[Russel Winder]

David,

On Sun, 2011-02-27 at 10:40 -0500, dsimcha wrote:

> I realized the obvious kludge and "fixed" this.  Now, all benchmarks 
> take a --nCpu command line argument that allows you to set the number of 
> cores manually.  This is an absolute must if running on 64.  If you 
> don't set this, the default is whatever core.cpuid.coresPerCPU returns, 
> and on 64 bit this will always be 1.

I agree it is sad to have had to do this, core.cpuid.coresPerCPU should
be fixed and fixed asap.  In the interim using "--nCpu 8" with the
64-bit build on Ubuntu Maverick, I get:


        ========  euclidean  ============
        Serial reduce:  1154 milliseconds.
        Parallel reduce with 8 cores:  266 milliseconds.
        
        ========  matrixInversion  ============
        Inverted a 256 x 256 matrix serially in 62 milliseconds.
        Inverted a 256 x 256 matrix using 8 cores in 88 milliseconds.
        
        ========  millionSqrt  ============
        Parallel benchmarks being done with 8 cores.
        Did serial millionSqrt in 957 milliseconds.
        Did parallel foreach millionSqrt in 212 milliseconds.
        Did parallel map millionSqrt in 164 milliseconds.
        
        ========  parallelSort  ============
        Serial quick sort:  4548 milliseconds.
        Parallel quick sort:  1502 milliseconds.
        
        ========  pi  ============
        Calculated pi = 3.141596556 in 172 milliseconds serially.
        Calculated pi = 3.141596794 in 41 milliseconds using 8 cores.
        
        ========  pipelining  ============
        Did serial string -> float, euclid in 2047 milliseconds.
        Did parallel string -> float, euclid with 8 cores in 1756 milliseconds.


I get the feeling that the pi calculation is showing that the perhaps
the computations are too short to show proper scaling?

-- 
Russel.
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Dr Russel Winder      t: +44 20 7585 2200   voip: sip:russel.winder at ekiga.net
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