Re: [AMBER-Developers] ips.f::aips_sumrc() is not using nfftdim2 andnfftdim3

From: Mark Williamson <>
Date: Tue, 02 Feb 2010 14:47:43 -0800

Robert Duke wrote:
> Okay, be careful about dinking with nfft[123] vs nfftdim[123]. I have
> no idea whether this ips code is correct, but this nfft vs. nfftdim
> stuff has caused confusion before in the recip space code (notably, the
> guys doing the pmemd gpu port made some assumptions and renamed some
> stuff and majorly broke some code). I have not refreshed my memory by
> looking at code, but I vaguely remember that these two sets of variables
> exist due to use of half complex fft's in reciprocal space calcs, and
> you basically have to be able to treat different fft-related data
> structures as if they are dimensioned differently (I am sure that is as
> clear as mud - bottom line - don't dink with these variables unless you
> know what you are doing, and as far as I know, Mike Crowley, Tom Darden
> and I are the only folks who have done a lot with this stuff - though
> looks like ips folks waded into it a bit too...).
> Regards - Bob

Thanks Bob, I was not aware of this. It sounds quite esoteric; I assume
the motivation behind this was performance related? Are there any
documents expanding upon this?



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Received on Tue Feb 02 2010 - 15:00:02 PST
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