Do not check return values for MPI calls

The custom error handlers for each slave-master communicator will
handle errors in MPI_Recv() and MPI_Send() and eventually call
MPI_Abort(). So there is no need to check return values for these
MPI calls.

opm/simulators/flow/ReservoirCouplingMaster.cpp

@@ -150,7 +150,10 @@ receiveNextReportDateFromSlaves()
     if (this->comm_.rank() == 0) {
         for (unsigned int i = 0; i < num_slaves; i++) {
             double slave_next_report_time_offset; // Elapsed time from the beginning of the simulation
-            int result = MPI_Recv(
+            // NOTE: All slave-master communicators have set a custom error handler, which eventually
+            //   will call MPI_Abort() so there is no need to check the return value of any MPI_Recv()
+            //   or MPI_Send() calls.
+            MPI_Recv(
                 &slave_next_report_time_offset,
                 /*count=*/1,
                 /*datatype=*/MPI_DOUBLE,
@@ -159,9 +162,6 @@ receiveNextReportDateFromSlaves()
                 this->getSlaveComm(i),
                 MPI_STATUS_IGNORE
             );
-            if (result != MPI_SUCCESS) {
-                OPM_THROW(std::runtime_error, "Failed to receive next report date from slave process");
-            }
             this->slave_next_report_time_offsets_[i] = slave_next_report_time_offset;
             OpmLog::info(
                 fmt::format(

opm/simulators/flow/ReservoirCouplingSlave.cpp

@@ -48,6 +48,9 @@ ReservoirCouplingSlave(
     if (this->slave_master_comm_ == MPI_COMM_NULL) {
         OPM_THROW(std::runtime_error, "Slave process is not spawned by a master process");
     }
+    // NOTE: By installing a custom error handler for all slave-master communicators, which
+    //   eventually will call MPI_Abort(), there is no need to check the return value of any
+    //   MPI_Recv() or MPI_Send() calls as errors will be caught by the error handler.
     ReservoirCoupling::setErrhandler(this->slave_master_comm_, /*is_master=*/false);
 }
 
@@ -56,7 +59,10 @@ ReservoirCouplingSlave::
 receiveNextTimeStepFromMaster() {
     double timestep;
     if (this->comm_.rank() == 0) {
-        int result = MPI_Recv(
+        // NOTE: All slave-master communicators have set a custom error handler, which eventually
+        //   will call MPI_Abort() so there is no need to check the return value of any MPI_Recv()
+        //   or MPI_Send() calls.
+        MPI_Recv(
             &timestep,
             /*count=*/1,
             /*datatype=*/MPI_DOUBLE,
@@ -65,9 +71,6 @@ receiveNextTimeStepFromMaster() {
             this->slave_master_comm_,
             MPI_STATUS_IGNORE
         );
-        if (result != MPI_SUCCESS) {
-            OPM_THROW(std::runtime_error, "Failed to receive next time step from master");
-        }
         OpmLog::info(
             fmt::format("Slave rank 0 received next timestep {} from master.", timestep)
         );
@@ -84,7 +87,10 @@ receiveMasterGroupNamesFromMasterProcess() {
     std::vector<char> group_names;
     if (this->comm_.rank() == 0) {
         MPI_Aint asize = 0;
-        int result = MPI_Recv(
+        // NOTE: All slave-master communicators have set a custom error handler, which eventually
+        //   will call MPI_Abort() so there is no need to check the return value of any MPI_Recv()
+        //   or MPI_Send() calls.
+        MPI_Recv(
             &asize,
             /*count=*/1,
             /*datatype=*/MPI_AINT,
@@ -94,15 +100,11 @@ receiveMasterGroupNamesFromMasterProcess() {
             MPI_STATUS_IGNORE
         );
         OpmLog::info("Received master group names size from master process rank 0");
-        if (result != MPI_SUCCESS) {
-            OPM_THROW(std::runtime_error,
-                      "Failed to receive master group names (size) from master process");
-        }
         // NOTE: MPI_Aint and std::size_t should be compatible on most systems, but we will
         //     cast it to std::size_t to avoid any potential issues
         size = static_cast<std::size_t>(asize);
         group_names.resize(size);
-        int result2 = MPI_Recv(
+        MPI_Recv(
             group_names.data(),
             /*count=*/size,
             /*datatype=*/MPI_CHAR,
@@ -111,10 +113,6 @@ receiveMasterGroupNamesFromMasterProcess() {
             this->slave_master_comm_,
             MPI_STATUS_IGNORE
         );
-        if (result2 != MPI_SUCCESS) {
-            OPM_THROW(std::runtime_error,
-                      "Failed to receive master group names from master process");
-        }
         OpmLog::info("Received master group names from master process rank 0");
     }
     this->comm_.broadcast(&size, /*count=*/1, /*emitter_rank=*/0);
@@ -136,6 +134,9 @@ sendNextReportDateToMasterProcess() const
         // NOTE: This is an offset in seconds from the start date, so it will be 0 if the next report
         //      would be the start date. In general, it should be a positive number.
         double next_report_time_offset = elapsed_time + current_step_length;
+        // NOTE: All slave-master communicators have set a custom error handler, which eventually
+        //   will call MPI_Abort() so there is no need to check the return value of any MPI_Recv()
+        //   or MPI_Send() calls.
         MPI_Send(
             &next_report_time_offset,
             /*count=*/1,
@@ -155,6 +156,9 @@ sendActivationDateToMasterProcess() const
     if (this->comm_.rank() == 0) {
         // NOTE: The master process needs the s
         double activation_date = this->getGrupSlavActivationDate_();
+        // NOTE: All slave-master communicators have set a custom error handler, which eventually
+        //   will call MPI_Abort() so there is no need to check the return value of any MPI_Recv()
+        //   or MPI_Send() calls.
         MPI_Send(
             &activation_date,
             /*count=*/1,
@@ -174,6 +178,9 @@ sendSimulationStartDateToMasterProcess() const
     if (this->comm_.rank() == 0) {
         // NOTE: The master process needs the s
         double start_date = this->schedule_.getStartTime();
+        // NOTE: All slave-master communicators have set a custom error handler, which eventually
+        //   will call MPI_Abort() so there is no need to check the return value of any MPI_Recv()
+        //   or MPI_Send() calls.
         MPI_Send(
             &start_date,
             /*count=*/1,

opm/simulators/flow/ReservoirCouplingSpawnSlaves.cpp

@@ -154,7 +154,10 @@ receiveActivationDateFromSlaves_()
     if (this->comm_.rank() == 0) {
         for (unsigned int i = 0; i < num_slaves; i++) {
             double slave_activation_date;
-            int result = MPI_Recv(
+            // NOTE: All slave-master communicators have set a custom error handler, which eventually
+            //   will call MPI_Abort() so there is no need to check the return value of any MPI_Recv()
+            //   or MPI_Send() calls.
+            MPI_Recv(
                 &slave_activation_date,
                 /*count=*/1,
                 /*datatype=*/MPI_DOUBLE,
@@ -163,9 +166,6 @@ receiveActivationDateFromSlaves_()
                 this->master_.getSlaveComm(i),
                 MPI_STATUS_IGNORE
             );
-            if (result != MPI_SUCCESS) {
-                OPM_THROW(std::runtime_error, "Failed to receive activation date from slave process");
-            }
             if (slave_activation_date < this->master_.getActivationDate()) {
                 OPM_THROW(std::runtime_error, "Slave process start date is earlier than "
                                               "the master process' activation date");
@@ -188,7 +188,10 @@ receiveSimulationStartDateFromSlaves_()
     if (this->comm_.rank() == 0) {
         for (unsigned int i = 0; i < num_slaves; i++) {
             double slave_start_date;
-            int result = MPI_Recv(
+            // NOTE: All slave-master communicators have set a custom error handler, which eventually
+            //   will call MPI_Abort() so there is no need to check the return value of any MPI_Recv()
+            //   or MPI_Send() calls.
+            MPI_Recv(
                 &slave_start_date,
                 /*count=*/1,
                 /*datatype=*/MPI_DOUBLE,
@@ -197,9 +200,6 @@ receiveSimulationStartDateFromSlaves_()
                 this->master_.getSlaveComm(i),
                 MPI_STATUS_IGNORE
             );
-            if (result != MPI_SUCCESS) {
-                OPM_THROW(std::runtime_error, "Failed to receive start date from slave process");
-            }
             this->master_.addSlaveStartDate(slave_start_date);
             OpmLog::info(
                 fmt::format(
@@ -227,6 +227,9 @@ sendMasterGroupNamesToSlaves_()
         for (unsigned int i = 0; i < num_slaves; i++) {
             auto slave_name = this->master_.getSlaveName(i);
             auto [group_names, size] = this->getMasterGroupNamesForSlave_(slave_name);
+            // NOTE: All slave-master communicators have set a custom error handler, which eventually
+            //   will call MPI_Abort() so there is no need to check the return value of any MPI_Recv()
+            //   or MPI_Send() calls.
             // NOTE: size should be of type std::size_t, so we can safely cast it to MPI_AINT
             MPI_Send(
                 &size,
@@ -312,6 +315,9 @@ spawnSlaveProcesses_()
             }
             OPM_THROW(std::runtime_error, "Failed to spawn slave process");
         }
+        // NOTE: By installing a custom error handler for all slave-master communicators, which
+        //   eventually will call MPI_Abort(), there is no need to check the return value of any
+        //   MPI_Recv() or MPI_Send() calls as errors will be caught by the error handler.
         ReservoirCoupling::setErrhandler(master_slave_comm, /*is_master=*/true);
         OpmLog::info(
             fmt::format(