[petsc-users] VecDot usage in parallel

[Zafer Leylek]

I have recently started using petsc and have little experience with parallel programming.

I am having problem with the following section of my code:

        KSPGetPC(ksp,&pc);
        PCSetType(pc,PCCHOLESKY);
        PCFactorSetMatSolverPackage(pc,MATSOLVERMUMPS);
        PCFactorSetUpMatSolverPackage(pc);
        PCFactorGetMatrix(pc,&L);
        MatMumpsSetIcntl(L,7,2);
        MatMumpsSetCntl(L,1,0.0);
        MatMumpsSetIcntl(L,33,1);
        KSPSetUp(ksp);
        KSPSolve(ksp, y, alpha);

        VecDot(y, alpha, &sigma);

when I run it using a single processor (mpiexec -np 1 ....) I get the correct answer, when I run using 2 processors I get sigma = 4*sigma and so on.

How can I solve this problem??

ZL


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