[BL/MPI] Reduce ifdef range.

BaseLib/MPI.h

@@ -5,28 +5,28 @@
  *            Distributed under a Modified BSD License.
  *              See accompanying file LICENSE.txt or
  *              http://www.opengeosys.org/project/license
- *
  */
 
 #pragma once
 
+#ifdef USE_PETSC
+#include <mpi.h>
+#endif
+
 namespace BaseLib::MPI
 {
 
-#ifdef USE_PETSC
-// Reduce operations for interprocess communications while using Petsc
-static inline int reduceMin(int val)
+static inline int reduceMin(int const val)
 {
+#ifdef USE_PETSC
+    // Reduce operations for interprocess communications while using Petsc
     int result;
     MPI_Allreduce(&val, &result, 1, MPI_INTEGER, MPI_MIN, PETSC_COMM_WORLD);
     return result;
-}
 #else
-// Reduce operations for interprocess communications without using Petsc
-static inline int reduceMin(int val)
-{
+    // Reduce operations for interprocess communications without using Petsc
     return val;
-}
 #endif
+}
 
 }  // namespace BaseLib::MPI