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-   -   Purpose of the -parallel parameter (http://www.cfd-online.com/Forums/openfoam-solving/99234-purpose-parallel-parameter.html)

GerhardHolzinger March 29, 2012 04:17

Purpose of the -parallel parameter
 
Hello,

I am running a parallel job and I forgot the -parallel parameter, so my command to start the simulation looked like this

mpirun -np 4 twoPhaseEulerFoam

The simulation runs and the system monitor tells me that there are in fact 4 processes running. The only difference to a normal parallel run is, that in the processor* folders there is only a 0 and a constant folder.
The computed time steps are stored in the case directory.

Can anyone describe what exactly happens if I omit the -parallel parameter?
I guess storing the field-information every time step requires some time, but running reconstructPar after the computation also does.

niklas March 29, 2012 04:26

without -parallel the processors will run the same job (in serial)

try running 'mpirun -np 4 ls'

it will run the same ls-command 4 times, on each processor.

GerhardHolzinger March 29, 2012 05:56

Thanks

your example is very enlightening


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