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Multithreaded external routines for IDL/WinNT



Stein Vidar's good advice to Remy Indebetouw about a multiprocessing external
routine on IDL/SGI, namely "Why not just try it?", gave me the nudge to act
like a proper IDL explorer and "just try it" on WinNT.

And indeed it works!
(BTW, sorry Remy, I don't know anything about doing this on IRIX.)

Here's a small example, icluding C source (plus 3-liner .DEF file!), IDL test
program, and binary .DLL:  ftp://demsyd.syd.dem.csiro.au/pub/idl/emmex.zip
I've done some testing on my dual PII/300 and in the pointless but
CPU-intensive calculation I'm doing in the test program, the benefit of using
2 CPUs instead of 1 actually hits the ideal 2*!

My apologies if this is old hat to any IDL users out there (BTW, where WERE
you - why couldn't we tease a response out of you?), but this was news to me,
and it's been pretty satisfying to be able to max out (from IDL) both of the
CPUs that have just been keeping my office warm these last few months.	I'd
always thought along the lines of:  "It can't be done ... IDL won't be having
with threads ... Runtime-libraries will fight", etc, but it doesn't appear to
be the case at all, at least on NT.  Actually, when Steven Johnson pointed
out that FFTW could go multithreaded I started wondering about this stuff. 
(BTW, thanks for being tactful, Steven.  I haven't done the benchmark for
Intel MKL vs FFTW, but after having looked at the FFTW web page and benchmark
results more closely, I've got a mild but growing unease that my posting
along the lines of "Hey, if you want fast FFT why not check out the Intel
MKL" might turn out to be reminiscent, somehow, of a line from a Johnny Bravo
cartoon;  goes something like this...  Johnny to a group of feminist
activists: "Gee, I didn't know that chicks like to vote."  :-)


Peter Mason

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