Fixed signature of the Allreduce method of communicators

src/TNL/Communicators/MpiCommunicator.h

@@ -310,14 +310,14 @@ class MpiCommunicator
         }
 
         template< typename T >
-        static void Allreduce( T* data,
+        static void Allreduce( const T* data,
                                T* reduced_data,
                                int count,
                                const MPI_Op &op,
                                CommunicationGroup group)
         {
 #ifdef HAVE_MPI
-            MPI_Allreduce( (void*) data, (void*) reduced_data,count,MPIDataType(data),op,group);
+            MPI_Allreduce( (const void*) data, (void*) reduced_data,count,MPIDataType(data),op,group);
 #else
             throw Exceptions::MPISupportMissing();
 #endif

src/TNL/Communicators/NoDistrCommunicator.h

@@ -108,13 +108,13 @@ class NoDistrCommunicator
       }
 
       template< typename T >
-      static void Allreduce( T* data,
+      static void Allreduce( const T* data,
                              T* reduced_data,
                              int count,
                              const MPI_Op &op,
                              CommunicationGroup group )
       {
-         memcpy( ( void* ) reduced_data, ( void* ) data, count * sizeof( T ) );
+         memcpy( ( void* ) reduced_data, ( const void* ) data, count * sizeof( T ) );
       }
 
       template< typename T >