Using IPstream and OPstream
 

Hello cfd-online community,
my name is Roman I'm new to this forum; right now I'm working on my Master thesis which involves some parallel programming in OpenFoam. I'm used to program with MPI but struggling a little bit with the Pstream lib. My problem is the following I just try to exchange some fields between the processes but when running the code bellow a deadlock occurs. So the idea is, if we have 4 processes, process 0 receives from process 3 and sends to process 1, process 1 recieves from process 0 and sends to process 2 and so on... With MPI I could just use MPI_Sendrecv_replace. Would be nice if someone could give me a hint or maybe a samplecode where OPstream and IPstream is used.

Thanks in advance.

Roman

const int nProcs = UPstream::nProcs();

const int sendToProc = (Pstream::UPstream::myProcNo() + 1) % nProcs;
const int recFromProc = (Pstream::UPstream::myProcNo() + nProcs - 1) % nProcs;
vectorField cellNeighCenters = cellCenters;
vectorField jV = J*cellVolumes;

Field<vector> recvBuffer(J.size());

for( int i = 0; i < nProcs;i++ )
{

//////////
....
.... Some computations
....
/////////

if ( Pstream::UPstream::myProcNo() % 2 == 0 )
{

OPstream sendStream
(
Pstream::blocking,
sendToProc,
sizeof(jV)
);

sendStream << jV << endl;
sendStream << cellNeighCenters << endl;

IPstream recieveStream
(
Pstream::blocking,
recFromProc,
sizeof(jV)
);

recieveStream >> recvBuffer;
jV = recvBuffer;

recieveStream >> recvBuffer;
cellNeighCenters = recvBuffer;
}
else
{
IPstream recieveStream
(
Pstream::blocking,
recFromProc,
sizeof(jV)
);

recieveStream >> recvBuffer;
jV = recvBuffer;

recieveStream >> recvBuffer;
cellNeighCenters = recvBuffer;

OPstream sendStream
(
Pstream::blocking,
sendToProc,
sizeof(jV)
);

sendStream << jV << endl;
sendStream << cellNeighCenters << endl;
}
}