adds debug printout

cpp/particles/p2p/p2p_distr_mpi.hpp

@@ -291,6 +291,7 @@ public:
 
         // Some processes might not be involved
         if(nb_processes_involved <= my_rank){
+            DEBUG_MSG("warning: nb_processes_involved <= my_rank, and this process is exiting p2p_distr_mpi::compute_distr now.\nHowever, there is a check below which calls an MPI_Gather over MPI_COMM_WORLD.\n");
             return;
         }
 
@@ -492,10 +493,14 @@ public:
             if(descriptor.isRecv == false){
                 whatNext.emplace_back(std::pair<Action,int>{NOTHING_TODO, -1});
                 mpiRequests.emplace_back();
-                AssertMpi(MPI_Isend(const_cast<partsize_t*>(&descriptor.nbParticlesToExchange),
-                                    1, particles_utils::GetMpiType(partsize_t()),
-                                    descriptor.destProc, TAG_NB_PARTICLES,
-                                    current_com, &mpiRequests.back()));
+                AssertMpi(MPI_Isend(
+                            const_cast<partsize_t*>(&descriptor.nbParticlesToExchange),
+                            1,
+                            particles_utils::GetMpiType(partsize_t()),
+                            descriptor.destProc,
+                            TAG_NB_PARTICLES,
+                            current_com,
+                            &mpiRequests.back()));
 #ifndef NDEBUG // Just for assertion
                 willsend[descriptor.destProc] += 1;
 #endif
@@ -581,6 +586,9 @@ public:
 
                 for(int idxproc = 0 ; idxproc < nb_processes_involved ; ++idxproc){
                     for(int idxtest = 0 ; idxtest < nb_processes_involved ; ++idxtest){
+                        DEBUG_MSG("p2p_distr_mpi::compute_distribution, comparing willsendall(%d, %d)=%d with willrecvall(%d, %d) = %d\n",
+                                idxproc, idxtest, willsendall[idxproc*nb_processes_involved + idxtest],
+                                idxtest, idxproc, willrecvall[idxtest*nb_processes_involved + idxproc]);
                         assert(willsendall[idxproc*nb_processes_involved + idxtest]
                                 == willrecvall[idxtest*nb_processes_involved + idxproc]);
                     }