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

From: David A Case <>
Date: Mon, 26 Jan 2015 10:09:27 -0500

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.


AMBER mailing list
Received on Mon Jan 26 2015 - 07:30:02 PST
Custom Search