[gmx-developers] Gromacs 4.6.3: Problems in replica exchange: wrongly exchange if temperatures of replicas are not in ascent order

[Shirts, Michael (mrs5pt)]

Thanks for the report!  I'll try to take a look at it today (or if not,
tomorrow -- at a conference today, but have available time on a long layover
tomorrow).  That may not be the right fix below. I'll see if I can replicate
it, but please upload your files to the redmine issue below -- it may very
well occur only under certain conditions.

Best,
~~~~~~~~~~~~
Michael Shirts
Assistant Professor
Department of Chemical Engineering
University of Virginia
michael.shirts at virginia.edu
(434)-243-1821


> From: David van der Spoel <spoel at xray.bmc.uu.se>
> Reply-To: Discussion list for GROMACS development <gmx-developers at gromacs.org>
> Date: Thu, 7 Nov 2013 08:17:59 +0100
> To: Discussion list for GROMACS development <gmx-developers at gromacs.org>
> Subject: Re: [gmx-developers] Gromacs 4.6.3: Problems in replica exchange:
> wrongly exchange if temperatures of replicas are not in ascent order
> 
> On 2013-11-07 00:09, Tianwu Zang wrote:
>> I found that when doing replica exchange, serious problems will
>> happen if temperatures of replicas are not in ascent order. For example,
>> the temperature of replica 1 is 500K while the one in replica 2 is 300K,
>> then even if the exchange request is denied(as shown in the log file),
>> two copies are still exchanged.
>> I suggest to modify line 1258~1259:
>> 
>> if( destinations[i] != i)
>>    bAnyReplicaExchanged = TRUE;
>> 
>> into
>> 
>> if( destinations[i] != re->ind[i])
>>    bAnyReplicaExchanged = TRUE;
>> 
>> because if temperatures of replicas are not in ascent order, re->ind[i]
>> is not equal to i, while in line 978, destinations[i] are initialized as
>> re->ind[i].
> Redmine issue created.
> http://redmine.gromacs.org/issues/1377
> 
> Could you please upload example files?
> 
> -- 
> David van der Spoel, Ph.D., Professor of Biology
> Dept. of Cell & Molec. Biol., Uppsala University.
> Box 596, 75124 Uppsala, Sweden. Phone: +46184714205.
> spoel at xray.bmc.uu.se    http://folding.bmc.uu.se
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