Dear all,
I think we found a problem when using REMD together with GB and RESPA.
In the "initremd" step, the "force" routine is called only once due to the
return statement around row 985 in runmd.f. If nrespa > 1, nonsense potential
energies are then returned to "subrem". In our case, these energies were
large and positive and very similar, which leads to an almost random exchange
of replica in the first exchange step. This happens every time a remd is
re-started.
A solution may be to set irespa according to
!--------------------------------------------------------------
! ---Step 1b: Get the forces for the current coordinates:
!--------------------------------------------------------------
npbstep = nstep
iprint = 0
if( nstep == 0 .or. nstep+1 == nstlim ) iprint = 1
! TIME_force is started and stopped inside force
if( initremd ) then
irespa = 0
^^^^^^
end if
call force(xx,ix,ih,ipairs,x,f,ener(23),vir, &
xx(l96),xx(l97),xx(l98),xx(l99), qsetup,qpsander, &
do_list_update)
! Constant pH transition evaluation
if ((icnstph /= 0) .and. (mod(irespa,ntcnstph) == 0)) then
call cnstphendstep(ix(icpstinf),ix(icpresst),ix(icpptcnt), &
ix(icptrsct), xx(lcpene),xx(lcpcrg),xx(l190),xx(l15),ener(39), &
icpselres,icpselstat,cnstph_rand_gen)
call cnstphwrite(ix(icpresst),icpselres,ix(icptrsct))
end if
if( initremd ) then
irespa = 1
^^^^^^
end if
in runmd.f to get full energies calculated in the first step already. As I am
not that familiar with the remd implementation, would someone confirm this?
If it's fine I will send a patch.
Best regards
Holger
--
++++++++++++++++++++++++++++++++++++++++++++++++++
Dr. Holger Gohlke
Juniorprofessor fuer Molekulare Bioinformatik
J.W. Goethe-Universitaet
Fachbereich Biowissenschaften
Institut fuer Zellbiologie und Neurowissenschaft
Max-von-Laue-Str. 9
60438 Frankfurt/Main
Germany
Tel.: (+49) 69-798-29411; Fax: (+49) 69-798-29527
Email: gohlke.bioinformatik.uni-frankfurt.de
URL: http://mbilab.uni-frankfurt.de
++++++++++++++++++++++++++++++++++++++++++++++++++
Received on Sun Aug 26 2007 - 06:07:21 PDT
