Hi all,

I'm having some trouble running simulations with increasing number of CPUs. What parameters should I modify to make sure that the simulation would run with a specific number of processors? Or, having access to a large number of processors, how to select the number of CPUs to request?

Besides this, should the PP/PME reported by grompp always fall in the range 0.25-0.33? What if it is lower (e.g., 0.16)?

I'm attaching an mdrun logfile of a failed run.

Thanks for suggestions,
Pablo

--
Pablo Englebienne, PhD
Institute of Complex Molecular Systems (ICMS)
Eindhoven University of Technology, TU/e
PO Box 513, HG -1.26
5600 MB Eindhoven, The Netherlands
Tel +31 40 247 5349

Log file opened on Mon Nov  2 18:23:16 2009
Host: node052  pid: 22760  nodeid: 0  nnodes:  16
The Gromacs distribution was built Thu Oct 29 14:19:59 CET 2009 by
pengle...@st-hpc-main (Linux 2.6.18-128.7.1.el5 x86_64)


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++++ PLEASE READ AND CITE THE FOLLOWING REFERENCE ++++
B. Hess and C. Kutzner and D. van der Spoel and E. Lindahl
GROMACS 4: Algorithms for highly efficient, load-balanced, and scalable
molecular simulation
J. Chem. Theory Comput. 4 (2008) pp. 435-447
-------- -------- --- Thank You --- -------- --------


++++ PLEASE READ AND CITE THE FOLLOWING REFERENCE ++++
D. van der Spoel, E. Lindahl, B. Hess, G. Groenhof, A. E. Mark and H. J. C.
Berendsen
GROMACS: Fast, Flexible and Free
J. Comp. Chem. 26 (2005) pp. 1701-1719
-------- -------- --- Thank You --- -------- --------


++++ PLEASE READ AND CITE THE FOLLOWING REFERENCE ++++
E. Lindahl and B. Hess and D. van der Spoel
GROMACS 3.0: A package for molecular simulation and trajectory analysis
J. Mol. Mod. 7 (2001) pp. 306-317
-------- -------- --- Thank You --- -------- --------


++++ PLEASE READ AND CITE THE FOLLOWING REFERENCE ++++
H. J. C. Berendsen, D. van der Spoel and R. van Drunen
GROMACS: A message-passing parallel molecular dynamics implementation
Comp. Phys. Comm. 91 (1995) pp. 43-56
-------- -------- --- Thank You --- -------- --------

parameters of the run:
   integrator           = md
   nsteps               = 50000
   init_step            = 0
   ns_type              = Grid
   nstlist              = 5
   ndelta               = 2
   nstcomm              = 1
   comm_mode            = Linear
   nstlog               = 1000
   nstxout              = 1000
   nstvout              = 1000
   nstfout              = 0
   nstenergy            = 1000
   nstxtcout            = 0
   init_t               = 0
   delta_t              = 0.002
   xtcprec              = 1000
   nkx                  = 40
   nky                  = 40
   nkz                  = 40
   pme_order            = 4
   ewald_rtol           = 1e-05
   ewald_geometry       = 0
   epsilon_surface      = 0
   optimize_fft         = FALSE
   ePBC                 = xyz
   bPeriodicMols        = FALSE
   bContinuation        = TRUE
   bShakeSOR            = FALSE
   etc                  = V-rescale
   epc                  = Parrinello-Rahman
   epctype              = Isotropic
   tau_p                = 5
   ref_p (3x3):
      ref_p[    0]={ 1.00000e+00,  0.00000e+00,  0.00000e+00}
      ref_p[    1]={ 0.00000e+00,  1.00000e+00,  0.00000e+00}
      ref_p[    2]={ 0.00000e+00,  0.00000e+00,  1.00000e+00}
   compress (3x3):
      compress[    0]={ 1.00000e-04,  0.00000e+00,  0.00000e+00}
      compress[    1]={ 0.00000e+00,  1.00000e-04,  0.00000e+00}
      compress[    2]={ 0.00000e+00,  0.00000e+00,  1.00000e-04}
   refcoord_scaling     = No
   posres_com (3):
      posres_com[0]= 0.00000e+00
      posres_com[1]= 0.00000e+00
      posres_com[2]= 0.00000e+00
   posres_comB (3):
      posres_comB[0]= 0.00000e+00
      posres_comB[1]= 0.00000e+00
      posres_comB[2]= 0.00000e+00
   andersen_seed        = 815131
   rlist                = 1.4
   rtpi                 = 0.05
   coulombtype          = PME
   rcoulomb_switch      = 0
   rcoulomb             = 1.4
   vdwtype              = Cut-off
   rvdw_switch          = 0
   rvdw                 = 1.4
   epsilon_r            = 1
   epsilon_rf           = 1
   tabext               = 1
   implicit_solvent     = No
   gb_algorithm         = Still
   gb_epsilon_solvent   = 80
   nstgbradii           = 1
   rgbradii             = 2
   gb_saltconc          = 0
   gb_obc_alpha         = 1
   gb_obc_beta          = 0.8
   gb_obc_gamma         = 4.85
   sa_surface_tension   = 2.092
   DispCorr             = EnerPres
   free_energy          = no
   init_lambda          = 0
   sc_alpha             = 0
   sc_power             = 0
   sc_sigma             = 0.3
   delta_lambda         = 0
   nwall                = 0
   wall_type            = 9-3
   wall_atomtype[0]     = -1
   wall_atomtype[1]     = -1
   wall_density[0]      = 0
   wall_density[1]      = 0
   wall_ewald_zfac      = 3
   pull                 = no
   disre                = No
   disre_weighting      = Conservative
   disre_mixed          = FALSE
   dr_fc                = 1000
   dr_tau               = 0
   nstdisreout          = 100
   orires_fc            = 0
   orires_tau           = 0
   nstorireout          = 100
   dihre-fc             = 1000
   em_stepsize          = 0.01
   em_tol               = 10
   niter                = 20
   fc_stepsize          = 0
   nstcgsteep           = 1000
   nbfgscorr            = 10
   ConstAlg             = Lincs
   shake_tol            = 0.0001
   lincs_order          = 4
   lincs_warnangle      = 30
   lincs_iter           = 1
   bd_fric              = 0
   ld_seed              = 1993
   cos_accel            = 0
   deform (3x3):
      deform[    0]={ 0.00000e+00,  0.00000e+00,  0.00000e+00}
      deform[    1]={ 0.00000e+00,  0.00000e+00,  0.00000e+00}
      deform[    2]={ 0.00000e+00,  0.00000e+00,  0.00000e+00}
   userint1             = 0
   userint2             = 0
   userint3             = 0
   userint4             = 0
   userreal1            = 0
   userreal2            = 0
   userreal3            = 0
   userreal4            = 0
grpopts:
   nrdf:     231.858     4661.14
   ref_t:         300         300
   tau_t:         0.1         0.1
anneal:          No          No
ann_npoints:           0           0
   acc:	           0           0           0
   nfreeze:           N           N           N
   energygrp_flags[  0]: 0
   efield-x:
      n = 0
   efield-xt:
      n = 0
   efield-y:
      n = 0
   efield-yt:
      n = 0
   efield-z:
      n = 0
   efield-zt:
      n = 0
   bQMMM                = FALSE
   QMconstraints        = 0
   QMMMscheme           = 0
   scalefactor          = 1
qm_opts:
   ngQM                 = 0

Initializing Domain Decomposition on 16 nodes
Dynamic load balancing: auto
Will sort the charge groups at every domain (re)decomposition
Initial maximum inter charge-group distances:
    two-body bonded interactions: 0.589 nm, LJ-14, atoms 65 87
  multi-body bonded interactions: 0.538 nm, G96Angle, atoms 62 65
Minimum cell size due to bonded interactions: 0.591 nm
Maximum distance for 5 constraints, at 120 deg. angles, all-trans: 0.765 nm
Estimated maximum distance required for P-LINCS: 0.765 nm
This distance will limit the DD cell size, you can override this with -rcon
Guess for relative PME load: 0.31
Will use 10 particle-particle and 6 PME only nodes
This is a guess, check the performance at the end of the log file
Using 6 separate PME nodes
Scaling the initial minimum size with 1/0.8 (option -dds) = 1.25
Optimizing the DD grid for 10 cells with a minimum initial size of 0.956 nm
The maximum allowed number of cells is: X 3 Y 3 Z 3

-------------------------------------------------------
Program mdrun_openmpi, VERSION 4.0.5
Source code file: domdec.c, line: 5873

Fatal error:
There is no domain decomposition for 10 nodes that is compatible with the given box and a minimum cell size of 0.95625 nm
Change the number of nodes or mdrun option -rcon or -dds or your LINCS settings
Look in the log file for details on the domain decomposition
-------------------------------------------------------

"If You Want Something Done You Have to Do It Yourself" (Highlander II)

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