Add `fmpi_mpi_world_size()`

include/internal/fmpi_mpi.h

@@ -243,6 +243,10 @@ int fmpi_mpi_world_reduce_in_place(
 int fmpi_mpi_dims_create(
     const struct fmpi_mpi_ctx * ctx, size_t * const dim_len, size_t dim_cnt
 );
+/*------------------------------------------------------------------------------
+    fmpi_mpi_world_size()
+------------------------------------------------------------------------------*/
+int fmpi_mpi_world_size(const struct fmpi_mpi_ctx * ctx);
 /*==============================================================================
     GUARD
 ==============================================================================*/

src/fmpi_mpi.c

@@ -336,3 +336,17 @@ int fmpi_mpi_dims_create(
     }
     return fmpi_mpi_check_error(ctx, err, "MPI_Dims_create");
 }
+/*------------------------------------------------------------------------------
+    fmpi_mpi_world_size()
+------------------------------------------------------------------------------*/
+int fmpi_mpi_world_size(const struct fmpi_mpi_ctx * const ctx)
+{
+    assert(ctx != NULL);
+    int size = FMPI_ERROR;
+    int err = MPI_Comm_size(ctx->world, &size);
+    err = fmpi_mpi_check_error(ctx, err, "MPI_Comm_size");
+    if(err != FMPI_SUCCESS) {
+        return err;
+    }
+    return size;
+}