Re: [AMBER] integer limit for nstlim

From: David A Case <>
Date: Wed, 9 Nov 2016 17:41:58 -0500

On Wed, Nov 09, 2016, Neale, Christopher Andrew wrote:

> As reported in this post:
> . pmemd fails for a
> number of steps larger than MAXINT (see below). I see the logic in
> Ross' reply, but I think it would be useful if amber detected this and
> gracefully exited with a notice that nstlim has to be less than MAXINT.
> $ grep nstlim
> nstlim=2500000000,
> $ pmemd -O -i -o MD1.out -p this.prmtop -c EM.rst -r MD1.rst -x MD1.mdcrd -inf -l MD1.log
> At line 639 of file mdin_ctrl_dat.F90 (unit = 5, file = '')
> Fortran runtime error: Integer overflow while reading item 0

This would be a lot harder than you (might) think to code. The reading of
namelists is done by code provided by the compiler writers, not by amber
developers. Different compilers vary a lot in the user-friendliness of their
error messages.

There are various approaches that could be taken to get a better error
message, but the message above is not all that bad, in my view: It points you
to the exact line in the code where the error occurs, and indicates that
it is an integer overflow. There are *lots* of other places where Amber
fails to make good checks for bad inputs, and fixing those should probably
have a higher priority.


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Received on Wed Nov 09 2016 - 15:00:02 PST
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