Is it possible to change processor dimensions when read restart a file?

Submitted by J_Wang on Wed, 09/12/2012 - 19:30

Dear all,

I'm trying to change the processor size after I save the result from a serial version of LIGGGHTS and want to run the parallel version to continue the results. I define the prossessor dimensions before the read_restart comand but it shows an warning and error message as:

WARNING: Restart file used different 3d processor grid
orthogonal box = (-0.00106955 -0.00106955 -6.95546e-05) to (0.00106955 0.00106955 0.00206955)
ERROR: Bad grid of processors

Is it possible to change processor size when read restart a file? Would anyone give me some tips?

Best wishes

J.Wang

Forums:

tapsab | Wed, 09/12/2012 - 21:40

Its possible. I have done simulations where the first step used a single processor and after restart I would do the second step in parallel using multiple processors. I get the warning that you did but not the error. So I am guessing its just a matter of you providing the wrong processor grid. Maybe you want to try to just provide the total processors you want to use (not the processor dimensions) and let liggghts decide the grid to see if you still get the error.

ckloss's picture

ckloss | Sun, 09/16/2012 - 23:33

Hi,
as tapsab wrote, this is possible. The warning indicates possible round-off errors when re-starting with a different grid.
The error simply says that the processor grid as defined in the "processors" command does not match the #procs used for the mpirun command

Cheers, Christoph