Ok, I've cleaned up the Mlucas 2.6 source code and I think we're
ready to take a crack at a C version. The revised source (which
also includes a fix for a bug which David Willmore brought to
my attention - don't worry, it can only cause the code to quit
unexpectedly when it starts a new exponent as part of a multi-exponent
range test - any actual test results should be fine) is at
ftp://209.133.33.182/pub/mayer/Mlucas_2.6c.f90.gz
and Alpha and MIPS executables are also available in the .../pub/mayer/bin
directory at the above site. 2.6c also has some slightly improved memory
management - it's 5-10% faster on my Alpha 21064 and 21164 than 2.6b was.
With v2.5, Gord Palameta was
able (using an automated translator and subsequent manual work) to
get a decent C version in a remarkably short time; Brian Beuning
also created one, but we never did any head-to-head comparisons of
the two resulting codes.
This time, I'd like to keep some coherency to any such effort, so once
I see who offers to help, we can discuss how distribute the labor. Of course
anyone is free to go it alone, but I will ask Conrad Curry, who maintains
the GIMPS "other available source code" page to only post a link to a C
version if it gets my stamp of approval.
Potential benefits of an Mlucas.c:
1) Will run on any Unix platform; no special compiler should be needed
(though we need to find the best C compiler for each platform);
2) Will make it easier to interface with the eventual PrimeNet for Unix;
3) Will make it easier to interface with Peter Montgomery's Mfactor code;
4) Will allow us to try neat tricks like inlining cache-bypassing stores
(if the architecture supports such an operation) which might really
help speed the code on systems with small caches.
With that said, are there any volunteers? I'll of course be around to help
explain what-this-and-that in the F90 code means, but will be putting most
of my near-term effort into a P-1 factorer geared for large exponents.
Cheers,
Ernst
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