[dune-pdelab] Problems with MPI

[Dodwell, Timothy]

Dear All,


I am running the latest release of PDELab on a Mac OX 10.10.5. I am implementing a multilevel monte carlo algorithm which is wrapped around a general model (in this case linear elasticity which uses SEQ_CG_AMG_SSOR for the solver.)


All works well and is tested in series. I have now tried to simply parallelise a for loop which computes a number of independent samples (see below). getSample is a function which returns a quantity of interest from my model and nproc is the number of processors.


When I do this, all processors with rank from 0 to (nproc -2) return values of NaN. If I run the code on 1 processor all works ok.

Thanks in advance for your help!

Tim


int numSamples = N[L] / nproc + 1; // Compute number of samples on each processor (rounding up)


double * Ytmp = new double[numSamples];



double * Yroot = NULL;


if (rank == 0){ Yroot = new double[numSamples * nproc];    }



for (int i = 0; i < numSamples; i++){    Ytmp[i] = getSample(L,z);    }



MPI_Gather(Ytmp,numSamples,MPI_DOUBLE,Yroot,numSamples,MPI_DOUBLE,0,MPI_COMM_WORLD);



Dr Tim Dodwell

Lecturer in Engineering Mathematics

Rm 221 - Harrison Building

College of Engineering, Mathematics & Physical Sciences

University of Exeter

Exeter

Devon

EX4 4PY


mail: t.dodwell(at)exeter.ac.uk

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