Re: [AMBER] premed.MPI warning

From: Jason Swails <>
Date: Sun, 10 Jan 2016 11:43:33 -0500

I think it occurs because dihedral terms that are omitted in end-group (1-4) interactions have scaling factors set to 0. Since they are inverted upon reading, you get a divide by zero. Since they are never used, they have no effect.

The original explanation I heard was that this would immediately indicate whether there was a bug in excluding the 1-4s that should have been excluded.

I'm not sure if this has been adjusted, or when it was changed. But I know it used to behave that way.

All the best,

Jason M. Swails
Rutgers University
Postdoctoral Researcher
> On Jan 10, 2016, at 8:45 AM, David A Case <> wrote:
>> On Sun, Jan 10, 2016, George Tzotzos wrote:
>> Note: The following floating-point exceptions are signalling: IEEE_DIVIDE_BY_ZERO
> One would think you ought to be worried about this, but I've seen these and
> ignored them....never finding the origin.
> If you can create a short run that illustrates the problem, you could post the
> files and we will try to reproduce it.  (We'd need to know compiler details,
> etc.)  Alternatively, compile a debug version of whatever program it is you
> are running (sander? pmemd?) and see if that gives you more detailed
> information.
> ....dac
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Received on Sun Jan 10 2016 - 09:00:03 PST
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