diy: pass operator instance to mpi_op<>::get()

This makes it possible to add custom MPI reduction operations without
having to add too complex logic to allocating and freeing MPI operation.

diy/include/diy/mpi/collectives.hpp

@@ -152,13 +152,13 @@ namespace mpi
       }
     }
 
-    static void reduce(const communicator& comm, const T& in, T& out, int root, const Op&)
+    static void reduce(const communicator& comm, const T& in, T& out, int root, const Op& op)
     {
       MPI_Reduce(Datatype::address(const_cast<T&>(in)),
                  Datatype::address(out),
                  Datatype::count(in),
                  Datatype::datatype(),
-                 detail::mpi_op<Op>::get(),
+                 detail::mpi_op<Op>::get(op),
                  root, comm);
     }
 
@@ -168,38 +168,38 @@ namespace mpi
                  Datatype::address(const_cast<T&>(in)),
                  Datatype::count(in),
                  Datatype::datatype(),
-                 detail::mpi_op<Op>::get(),
+                 detail::mpi_op<Op>::get(op),
                  root, comm);
     }
 
-    static void all_reduce(const communicator& comm, const T& in, T& out, const Op&)
+    static void all_reduce(const communicator& comm, const T& in, T& out, const Op& op)
     {
       MPI_Allreduce(Datatype::address(const_cast<T&>(in)),
                     Datatype::address(out),
                     Datatype::count(in),
                     Datatype::datatype(),
-                    detail::mpi_op<Op>::get(),
+                    detail::mpi_op<Op>::get(op),
                     comm);
     }
 
-    static void all_reduce(const communicator& comm, const std::vector<T>& in, std::vector<T>& out, const Op&)
+    static void all_reduce(const communicator& comm, const std::vector<T>& in, std::vector<T>& out, const Op& op)
     {
       out.resize(in.size());
       MPI_Allreduce(Datatype::address(const_cast<T&>(in[0])),
                     Datatype::address(out[0]),
                     in.size(),
                     Datatype::datatype(),
-                    detail::mpi_op<Op>::get(),
+                    detail::mpi_op<Op>::get(op),
                     comm);
     }
 
-    static void scan(const communicator& comm, const T& in, T& out, const Op&)
+    static void scan(const communicator& comm, const T& in, T& out, const Op& op)
     {
       MPI_Scan(Datatype::address(const_cast<T&>(in)),
                Datatype::address(out),
                Datatype::count(in),
                Datatype::datatype(),
-               detail::mpi_op<Op>::get(),
+               detail::mpi_op<Op>::get(op),
                comm);
     }
 

diy/include/diy/mpi/operations.hpp

@@ -14,13 +14,13 @@ namespace mpi
 
 namespace detail
 {
-  template<class T> struct mpi_op                           { static MPI_Op  get(); };
-  template<class U> struct mpi_op< maximum<U> >             { static MPI_Op  get() { return MPI_MAX; }  };
-  template<class U> struct mpi_op< minimum<U> >             { static MPI_Op  get() { return MPI_MIN; }  };
-  template<class U> struct mpi_op< std::plus<U> >           { static MPI_Op  get() { return MPI_SUM; }  };
-  template<class U> struct mpi_op< std::multiplies<U> >     { static MPI_Op  get() { return MPI_PROD; }  };
-  template<class U> struct mpi_op< std::logical_and<U> >    { static MPI_Op  get() { return MPI_LAND; }  };
-  template<class U> struct mpi_op< std::logical_or<U> >     { static MPI_Op  get() { return MPI_LOR; }  };
+  template<class T> struct mpi_op                           { static MPI_Op  get(const T&); };
+  template<class U> struct mpi_op< maximum<U> >             { static MPI_Op  get(const maximum<U>&) { return MPI_MAX; }  };
+  template<class U> struct mpi_op< minimum<U> >             { static MPI_Op  get(const minimum<U>&) { return MPI_MIN; }  };
+  template<class U> struct mpi_op< std::plus<U> >           { static MPI_Op  get(const std::plus<U>&) { return MPI_SUM; }  };
+  template<class U> struct mpi_op< std::multiplies<U> >     { static MPI_Op  get(const std::multiplies<U>&) { return MPI_PROD; }  };
+  template<class U> struct mpi_op< std::logical_and<U> >    { static MPI_Op  get(const std::logical_and<U>&) { return MPI_LAND; }  };
+  template<class U> struct mpi_op< std::logical_or<U> >     { static MPI_Op  get(const std::logical_or<U>&) { return MPI_LOR; }  };
 }
 }
 }