parallel optimizations based on number of memory controllers vs cpus

[Jay Norwood]

On Friday, 23 March 2012 at 13:56:09 UTC, Timon Gehr wrote:
> On program startup, do:
>
> ThreadPool.defaultPoolThreads(14); // or 13

Yes, thank you. I just tried adding that.  The gains aren't 
scaleable in this particular test, which is apparently dominated 
by cpu processing, but even here you can see incremental 
improvements at 13 vs 7 threads on all the numbers.  I'd probably 
have to identify operations that were being limited by memory 
accesses in order to see the type of gains stated in that other 
app.

  This is with default 7 threads

finished wcp_wcPointer! time: 98 ms
finished wcp_wcCtRegex! time: 1300 ms
finished wcp_wcRegex! time: 2946 ms
finished wcp_wcRegex2! time: 2687 ms
finished wcp_wcSlices! time: 157 ms
finished wcp_wcStdAscii! time: 225 ms


This is processing the same data with 1 thread

finished wcp_wcPointer! time: 188 ms
finished wcp_wcCtRegex! time: 2219 ms
finished wcp_wcRegex! time: 5951 ms
finished wcp_wcRegex2! time: 5502 ms
finished wcp_wcSlices! time: 318 ms
finished wcp_wcStdAscii! time: 446 ms

And this is processing the same data with 13 threads

finished wcp_wcPointer! time: 93 ms
finished wcp_wcCtRegex! time: 1110 ms
finished wcp_wcRegex! time: 2531 ms
finished wcp_wcRegex2! time: 2321 ms
finished wcp_wcSlices! time: 136 ms
finished wcp_wcStdAscii! time: 200 ms

These were from the tests uploaded at 
https://github.com/jnorwood/wc_test.

The only change in the program that is uploaded is to add the 
suggested
defaultPoolThreads(13) at the start of main;
at the start of main to change the ThreadPool default thread 
count.