[gmx-users] problem with mdrun performing replica exchange MD

[Berk Hess]

You need to supply the -np option.
In Gromacs 3.3 you don't need to set the -multi option,
and -multi does not take an argument.
If you use the CVS head branch, you need to set -np and -multi
both with an argument.

Berk.

>From: "OZGE ENGIN" <OZENGIN at KU.EDU.TR>
>Reply-To: Discussion list for GROMACS users <gmx-users at gromacs.org>
>To: gmx-users at gromacs.org
>Subject: Re: RE: [gmx-users] problem with mdrun performing replica exchange 
>MD
>Date: Fri, 23 Nov 2007 11:44:47 +0200
>
>Hi Berk,
>
>I indicated the number of replicas with -multi option. In additon, I have 
>compiled Gromacs with MPI support.
>
>I used the following command line:
>
>mdrun -s simul0.tpr -multi 16 -reseed -1 -replex 2500
>
>-----Original Message-----
>From: "Berk Hess" <gmx3 at hotmail.com>
>To: gmx-users at gromacs.org
>Date: Fri, 23 Nov 2007 10:36:57 +0100
>Subject: RE: [gmx-users] problem with mdrun performing replica exchange MD
>
>
>
>
> >From: "OZGE ENGIN" <OZENGIN at KU.EDU.TR>
> >Reply-To: Discussion list for GROMACS users <gmx-users at gromacs.org>
> >To: gmx-users at gromacs.org
> >Subject: [gmx-users] problem with mdrun performing replica exchange MD
> >Date: Fri, 23 Nov 2007 11:30:53 +0200
> >
> >Hi All,
> >
> >I am performing replica exchange molecular dynamics simulation(REMD). I
> >have 16 replicas each of which has a peptide with different conformation.
> >After obtaining .tpr files (at desired temperatures) for each replicas, I
> >loaded them via mdrun, but I got the following error:
> >
> >Fatal error:
> >Nothing to exchange with only one replica
> >-------------------------------------------
> >
> >Why?
>
>I guess there are two possibilities.
>Or you did not use the -np option of mdrun to set the number of replicas,
>or you have not compiled Gromacs with MPI support.
>
>Berk.
>
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