IO error running multiple walkers MPI

[Michael Jones]

Hello, I have been trying to run a walkers_mpi simulation on gromacs but am seeing:

File input/output error:
md_0_1.tpr

My plumed file is as follows:

ene: ENERGY
mc: ECV_MULTITHERMAL ARG=ene TEMP_MIN=270 TEMP_MAX=700
opes: OPES_EXPANDED ARG=mc.* PACE=500 WALKERS_MPI=ON

PRINT STRIDE=500 ARG=* FILE=COLVAR

I'm new to gromacs so the issue may lie there. I compiled with:

cmake -DGMX_BUILD_OWN_FFTW=ON -DGMX_MPI=ON -DGMX_GPU=CUDA

And my gromacs run command is below. If I do not specify the  -multidir flag then the simulation+plumed runs fine but without multiple walkers. 

mpirun -np 4 gmx_mpi mdrun -v -deffnm md_0_1 -plumed plumed.dat -multidir W_{1..4} 

I would appreciate any advice. Thank you.

-Mike

[Michele Invernizzi]

Hi Mike,

I think it should be just WALKERS_MPI and not WALKERS_MPI=ON, but this alone would give a different error.

I find the way gromacs deals with this -multidir option a little bit confusing, but I eventually have settled with using the following setup.

I usually place the plumed.dat file in the top folder, then the different tpr files (all with the same name) each in a separate subfolder. I run the simulation from the top folder, specifying -plumed ../plumed.dat, so that each of the walkers reads the same plumed file. 

I also add FILE=../DELTAFS to the OPES_EXPANDED line, to have the DELTAFS file in the top folder, otherwise by default it will be placed in W_1.

Hopefully this helps.

Best,

Michele

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[Michael Jones]

Great thank you it's working well!

For the record, this is full gromacs command, where each W_x directory contains the md_0.trp

mpirun -np 4 gmx_mpi mdrun -deffnm md_0 -plumed ../plumed.dat -multidir W_{1..4}