add mpi communicator option to mumps solver interface

src/Algorithm/LinearSolvers/IpMumpsSolverInterface.cpp

@@ -97,13 +97,11 @@ MumpsSolverInterface::MumpsSolverInterface()
    mumps_->job = -1; //initialize mumps
    mumps_->par = 1; //working host for sequential version
    mumps_->sym = 2; //general symmetric matrix
-   mumps_->comm_fortran = USE_COMM_WORLD;
 
 #ifndef IPOPT_MUMPS_NOMUTEX
    const std::lock_guard<std::mutex> lock(mumps_call_mutex);
 #endif
 
-   mumps_c(mumps_);
    mumps_->icntl[2] = 0;  // global info stream
    mumps_->icntl[3] = 0;  // print level
    mumps_ptr_ = (void*) mumps_;
@@ -180,6 +178,11 @@ void MumpsSolverInterface::RegisterOptions(
       "Threshold to consider a pivot at zero in detection of linearly dependent constraints with MUMPS.",
       0.0,
       "This is CNTL(3) in MUMPS.", true);
+   roptions->AddIntegerOption(
+      "mumps_mpi_communicator",
+      "MPI communicator used for matrix operations",
+      USE_COMM_WORLD,
+      "This sets the MPI communicator. MPI_COMM_WORLD is the default. Any other value should be the return value from MPI_Comm_c2f");
 }
 
 /// give name of MUMPS with version info
@@ -217,13 +220,24 @@ bool MumpsSolverInterface::InitializeImpl(
    options.GetIntegerValue("mumps_scaling", mumps_scaling_, prefix);
    options.GetNumericValue("mumps_dep_tol", mumps_dep_tol_, prefix);
 
+   MUMPS_STRUC_C* mumps_ = static_cast<MUMPS_STRUC_C*>(mumps_ptr_);
+
+#ifndef IPOPT_MUMPS_NOMUTEX
+   const std::lock_guard<std::mutex> lock(mumps_call_mutex);
+#endif
+
+   Index mpi_comm;
+   options.GetIntegerValue("mumps_mpi_communicator", mpi_comm, prefix);
+   mumps_->comm_fortran = static_cast<int>(mpi_comm);
+
+   mumps_c(mumps_);
+
    // Reset all private data
    initialized_ = false;
    pivtol_changed_ = false;
    refactorize_ = false;
    have_symbolic_factorization_ = false;
 
-   MUMPS_STRUC_C* mumps_ = static_cast<MUMPS_STRUC_C*>(mumps_ptr_);
    if( !warm_start_same_structure_ )
    {
       mumps_->n = 0;