[gmx-users] REMD problem

Mark Abraham Mark.Abraham at anu.edu.au
Thu Sep 29 01:38:31 CEST 2011


On 29/09/2011 7:20 AM, Justin A. Lemkul wrote:
>
>
> 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.

If the MPI configuration allows physical processors to be 
over-allocated, then GROMACS is none the wiser.

Mark

>
> -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
>




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