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Summary

Clang compiler errors with MPI_AllReduce (-Wtype-safety)

Steps to reproduce

-- The C compiler identification is Clang 9.0.1
-- The CXX compiler identification is Clang 9.0.1
-- Check for working C compiler: /opt/local/bin/mpicc-mpich-clang90

Relevant logs and/or screenshots

src/Algorithms/ParallelSliceTracker.cpp:291:41: error: argument type
      'bool *' doesn't match specified 'MPI' type tag that requires 'int *' [-Werror,-Wtype-safety]
            MPI_Allreduce(MPI_IN_PLACE, &globalEOL_m, 1, MPI_INT, MPI_LAND, Ippl::getComm());
                                        ^~~~~~~~~~~~     ~~~~~~~

src/Algorithms/bet/EnvelopeBunch.cpp:1458:33: error: argument type
      'size_t *' (aka 'unsigned long *') doesn't match specified 'MPI' type tag that requires 'long *'
      [-Werror,-Wtype-safety]
    MPI_Allreduce(MPI_IN_PLACE, &count, 1, MPI_LONG, MPI_SUM, Ippl::getComm());
                                ^~~~~~     ~~~~~~~~

3. some more similar to 2.

Possible fixes

https://gitlab.psi.ch/OPAL/src/blob/4868efe8cf31c3646c49387a293852acf215c2bb/src/Algorithms/ParallelSliceTracker.cpp#L291

MPI_Allreduce(MPI_IN_PLACE, &globalEOL_m, 1, MPI_INT, MPI_LAND, Ippl::getComm());

globalEOL_m is a boolean and this doesn't combine properly with MPI_INT.

Instead, the commented out line above:

reduce(&globalEOL_m, &globalEOL_m + 1, &globalEOL_m, OpBitwiseAndAssign());

compiles fine.

@kraus: there is a similar line in ParallelTTracker.cpp. Is that line correct in this case as well?

https://gitlab.psi.ch/OPAL/src/blob/4868efe8cf31c3646c49387a293852acf215c2bb/src/Algorithms/bet/EnvelopeBunch.cpp#L1458

MPI_Allreduce(MPI_IN_PLACE, &count, 1, MPI_LONG, MPI_SUM, Ippl::getComm());

should rather be:

MPI_Allreduce(MPI_IN_PLACE, &count, 1, MPI_UNSIGNED_LONG, MPI_SUM, Ippl::getComm());