Re: [AMBER] ERROR: nfft1 must be in the range of 6 to 512!

From: David A Case <>
Date: Thu, 8 Jun 2017 11:15:55 -0400

On Thu, Jun 08, 2017, Andreas Tosstorff wrote:
> I am running an umbrella sampling simulation and only for some windows I
> am coming across this nfft error (ERROR: nfft1 must be in the range
> of 6 to 512!...see below).

This is a rather arbitrary limit in the pmemd code. You can change
it by modifying the "gridhi" parameter in mdin_ewald_dat.F90 (in
$AMBERHOME/src/pmemd/src), then re-compiling. I've changed this to 1024
for large systems, and haven't seen any problems; but you should certainly
run some short simulations to look carefully for any problems after making
the change. (In particular, see what values of nfft1,2,3 you are getting.)

> Total vdw box size: 81.892 79.440 143.995 angstroms.

It's odd that you would get this error with such a relatively small system.
Is your volume changing a lot from these initial values? You can avoid
the exact stoppage by updating gridhi, but I'm concerned that something else
is wrong, especially related to the periodic box size.


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Received on Thu Jun 08 2017 - 08:30:04 PDT
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