[gmx-users] REMD problem

Justin A. Lemkul jalemkul at vt.edu
Wed Sep 28 23:20:42 CEST 2011



Liu, Liang wrote:
> Yes, they are updated like:
> ...
> Replica exchange at step 5700 time 11.4
> Repl ex  0    1 x  2    3 x  4    5 x  6    7    8    9 x 10   11 x 12   
> 13   14   15 x 16   17 x 18   19 x 20   21 x 22   23   24   25 x 26   27 
>   28   29 x 30   31   32   33 x 34   35   36   37 x 38   39   40   41 x 
> 42   43 x 44   45 x 46   47   48   49
> Repl pr        1.0       1.0       1.0       .00       1.0       1.0     
>   .00       1.0       1.0       1.0       1.0       .00       1.0       
> .00       1.0       .00       1.0       .00       .46       .00       
> 1.0       .78       1.0       .00
> 
> Replica exchange at step 5750 time 11.5
> Repl 0 <-> 1  dE = -7.583e+00
> Repl ex  0 x  1    2    3    4 x  5    6 x  7    8 x  9   10 x 11   12 x 
> 13   14 x 15   16 x 17   18 x 19   20   21   22   23   24 x 25   26   27 
>   28 x 29   30   31   32 x 33   34   35   36   37   38   39   40 x 41   
> 42 x 43   44   45   46   47   48   49
> Repl pr   1.0       .00       1.0       1.0       1.0       1.0       
> 1.0       1.0       1.0       1.0       .48       .11       1.0       
> .00       1.0       .00       1.0       .00       .00       .01       
> 1.0       1.0       .00       .01       .01
> 
>            Step           Time         Lambda
>            5800       11.60000        0.00000
> 
>    Energies (kJ/mol)
>           Angle    Proper Dih.  Improper Dih.          LJ-14     Coulomb-14
>     9.69806e+02    1.32207e+03    3.34938e+01    4.93171e+02   -3.91111e+03
>         LJ (SR)  Disper. corr.   Coulomb (SR)   Coul. recip. Position Rest.
>     3.14374e+04   -6.42258e+02   -1.88529e+05   -2.01604e+04    0.00000e+00
>       Potential    Kinetic En.   Total Energy  Conserved En.    Temperature
>    -1.78987e+05    4.57462e+04   -1.33240e+05    1.23302e+10    5.62201e+02
>  Pres. DC (bar) Pressure (bar)   Constr. rmsd
>    -2.12803e+02   -5.47109e+02    2.21484e-05
> ...
> 

Perhaps someone else can offer an explanation.  It should not be possible to run 
multiple replicas on a single processor.  Also note that your exchange 
probability is extremely high; you're likely not obtaining meaningful sampling.

-Justin

> On Wed, Sep 28, 2011 at 4:08 PM, Justin A. Lemkul <jalemkul at vt.edu 
> <mailto:jalemkul at vt.edu>> wrote:
> 
> 
> 
>     Liu, Liang wrote:
> 
>         Thanks. currently what I see is the program runs very slowly,
>         but get .log file for all the 50 replicas, does this mean all of
>         them are running?
> 
> 
>     Are the log files being updated, or do they all simply contain a
>     fatal error message that there are insufficient nodes?  I cannot
>     think of a reason why 50 simulations could possibly run on 2 processors.
> 
>     -Justin
> 
>         On Wed, Sep 28, 2011 at 3:41 PM, Justin A. Lemkul
>         <jalemkul at vt.edu <mailto:jalemkul at vt.edu>
>         <mailto:jalemkul at vt.edu <mailto:jalemkul at vt.edu>>> wrote:
> 
> 
> 
>            Liu, Liang wrote:
> 
>                Well, although this makes sense, why all the 50 replicas are
>                running when I run "mpirun
>                      -np 50 mdrun_mpi -s md.tpr -multi 50 -replex 50" on
>         my own
>                computer with only 2 cores?
> 
> 
>            I can offer no explanation for this behavior, but I expect that
>            either not all of them are actually running, or at the very least
>            you will get horribly slow performance.
> 
> 
>                By the way, would you please show me where I can find the
>                reasonable replex number information in the literature?
>          I did
>                not find it in the link you posted and the manual either.
> 
> 
>            A few minutes of real literature searching will be far more
>         valuable
>            than some random person on the Internet giving you a value
>         that you
>            blindly use ;)
> 
>            -Justin
> 
>                Thanks.
> 
> 
>                --         Best,
>                Liang Liu
> 
> 
>            --     ==============================____==========
> 
>            Justin A. Lemkul
>            Ph.D. Candidate
>            ICTAS Doctoral Scholar
>            MILES-IGERT Trainee
>            Department of Biochemistry
>            Virginia Tech
>            Blacksburg, VA
>            jalemkul[at]vt.edu <http://vt.edu> <http://vt.edu> | (540)
>         231-9080 <tel:%28540%29%20231-9080>
>            <tel:%28540%29%20231-9080>
> 
>            http://www.bevanlab.biochem.____vt.edu/Pages/Personal/justin
>         <http://vt.edu/Pages/Personal/justin>
>            <http://www.bevanlab.biochem.__vt.edu/Pages/Personal/justin
>         <http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin>>
> 
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>         -- 
>         Best,
>         Liang Liu
> 
> 
>     -- 
>     ==============================__==========
> 
>     Justin A. Lemkul
>     Ph.D. Candidate
>     ICTAS Doctoral Scholar
>     MILES-IGERT Trainee
>     Department of Biochemistry
>     Virginia Tech
>     Blacksburg, VA
>     jalemkul[at]vt.edu <http://vt.edu> | (540) 231-9080
>     <tel:%28540%29%20231-9080>
>     http://www.bevanlab.biochem.__vt.edu/Pages/Personal/justin
>     <http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin>
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> 
> -- 
> Best,
> Liang Liu

-- 
========================================

Justin A. Lemkul
Ph.D. Candidate
ICTAS Doctoral Scholar
MILES-IGERT Trainee
Department of Biochemistry
Virginia Tech
Blacksburg, VA
jalemkul[at]vt.edu | (540) 231-9080
http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin

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