Re: [AMBER] AMBER 14 DPFP single energy calculations inconsistent

From: R.G. Mantell <>
Date: Mon, 26 Jan 2015 15:34:13 +0000

I'm not doing a full minimisation. I am using imin = 1, maxcyc = 0, ncyc
   = 0, so would hope to get the same energy if I ran this same
calculation using DPFP several times. Running five times I get: EGB
=-119080.5069, EGB = -119072.8449, EGB = -119079.8208, EGB =
-119076.1230, EGB = -119073.7929
If I do this same test with another system, I get the same EGB energy
every time.



On 2015-01-26 15:09, David A Case wrote:
> On Mon, Jan 26, 2015, R.G. Mantell wrote:
>> I am having some problems with pmemd.cuda_DPFP in AMBER 14 and also
>> seeing the same problems in AMBER 12 with DPDP and SPDP precision
>> models. I have some input for which a single energy calculation does
>> not
>> yield the same energy each time I run it. Looking at min.out, it seems
>> that it is the EGB component which gives a different value each time.
>> This does not occur when using SPFP or the CPU version of AMBER. I do
>> not see this problem when using input for other systems. I have tried
>> the calculation on a Tesla K20m GPU and a GeForce GTX TITAN Black GPU
>> using several different versions of the CUDA toolkit. I see the same
>> problem with both igb=1 and igb=2. The input which causes the problem
>> can be found here:
> Can you say how different the values are on each run? What you
> describe is
> exactly what should be expected: parallel runs (and all GPU runs are
> highly
> parallel) with DPDP or SPDP are not deterministic, whereas Amber's SPFP
> is.
> On the other hand, if you are seeing significant differences between
> runs for
> DPDP, that might indicate a bug that needs to be examined.
> ...thx...dac
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Received on Mon Jan 26 2015 - 08:00:03 PST
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