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Old   June 19, 2020, 09:24
Default scatterList
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David Andersson
Join Date: Oct 2019
Posts: 46
Rep Power: 4
sippanspojk is on a distinguished road
Hi foamers,
I need help with scatterList because it is not doing what I want it to do. Below you see my code where I construct a list of size nProcs() on my master processor and then I scatter that list in hope to "deconstruct" the list and provide one chunk of the list to each processor, however that is not how it is working.

I run the case on two processors for the sake of easy while troubleshooting my code. I print the size of the list chunks before and after scattering to see how it changes and this is what it gives me:

Code:
Before scatter
[1] ESWLforField[0].size() = 0
[1] ESWLforField[1].size() = 0
[0] ESWLforField[0].size() = 248
[0] ESWLforField[1].size() = 104
After scatter
[0] ESWLforField[0].size() = 248
[0] ESWLforField[1].size() = 104
[1] ESWLforField[0].size() = 248
[1] ESWLforField[1].size() = 0
However, what I expected after scattering was:
Code:
[0] ESWLforField[0].size() = 248
[0] ESWLforField[1].size() = 104
[1] ESWLforField[0].size() = 0
[1] ESWLforField[1].size() = 104
what am I doing wrong here?

I would be very grateful if someone could help me out here.
Thanks,
David

SOLVED: I am now using listCombineScatter() instead of scatterList() and then it works fine.


Code:
if(Pstream::parRun()){
    Foam::List<Foam::List<scalar>> ESWLforField(Pstream::nProcs());
    if (Pstream::master()){
        for(int iProc=0; iProc<Pstream::nProcs(); iProc++){
            ESWLforField[iProc].setSize(nFacesPerProc[iProc],0.0);
        }

        int i = 0;
        for(int iProc=0; iProc<Pstream::nProcs(); iProc++){
            for(int iFace=0; iFace<nFacesPerProc[iProc]; iFace++){
                ESWLforField[iProc][iFace] = ESWLVec[i];
                i++;
            }
        }
    }

    Info << "Before scatter" << endl;
    Pout << "ESWLforField[0].size() = " << ESWLforField[0].size() << endl;
    Pout << "ESWLforField[1].size() = " << ESWLforField[1].size() << endl;

    Pstream::listCombineScatter(ESWLforField);

    Info << "After scatter" << endl;
    Pout << "ESWLforField[0].size() = " << ESWLforField[0].size() << endl;
    Pout << "ESWLforField[1].size() = " << ESWLforField[1].size() << endl;

Last edited by sippanspojk; June 24, 2020 at 09:35.
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