--- /dev/null
+/* Copyright (c) 2013-2014. The SimGrid Team.
+ * All rights reserved. */
+
+/* This program is free software; you can redistribute it and/or modify it
+ * under the terms of the license (GNU LGPL) which comes with this package. */
+
+#include "colls_private.h"
+//#include <star-reduction.c>
+
+int
+smpi_coll_tuned_reduce_flat_tree(void *sbuf, void *rbuf, int count,
+ MPI_Datatype dtype, MPI_Op op,
+ int root, MPI_Comm comm)
+{
+ int i, tag = COLL_TAG_REDUCE;
+ int size;
+ int rank;
+ MPI_Aint extent;
+ char *origin = 0;
+ char *inbuf;
+ MPI_Status status;
+
+ rank = smpi_comm_rank(comm);
+ size = smpi_comm_size(comm);
+
+ /* If not root, send data to the root. */
+ extent = smpi_datatype_get_extent(dtype);
+
+ if (rank != root) {
+ smpi_mpi_send(sbuf, count, dtype, root, tag, comm);
+ return 0;
+ }
+
+ /* Root receives and reduces messages. Allocate buffer to receive
+ messages. */
+
+ if (size > 1)
+ origin = (char *) smpi_get_tmp_recvbuffer(count * extent);
+
+
+ /* Initialize the receive buffer. */
+ if (rank == (size - 1))
+ smpi_mpi_sendrecv(sbuf, count, dtype, rank, tag,
+ rbuf, count, dtype, rank, tag, comm, &status);
+ else
+ smpi_mpi_recv(rbuf, count, dtype, size - 1, tag, comm, &status);
+
+ /* Loop receiving and calling reduction function (C or Fortran). */
+
+ for (i = size - 2; i >= 0; --i) {
+ if (rank == i)
+ inbuf = static_cast<char*>(sbuf);
+ else {
+ smpi_mpi_recv(origin, count, dtype, i, tag, comm, &status);
+ inbuf = origin;
+ }
+
+ /* Call reduction function. */
+ smpi_op_apply(op, inbuf, rbuf, &count, &dtype);
+
+ }
+
+ if (origin)
+ smpi_free_tmp_buffer(origin);
+
+ /* All done */
+ return 0;
+}