--- /dev/null
+#include "colls.h"
+/*****************************************************************************
+
+ * Function: alltoall_pair_mpi_barrier
+
+ * Return: int
+
+ * Inputs:
+ send_buff: send input buffer
+ send_count: number of elements to send
+ send_type: data type of elements being sent
+ recv_buff: receive output buffer
+ recv_count: number of elements to received
+ recv_type: data type of elements being received
+ comm: communicator
+
+ * Descrp: Function works when P is power of two. In each phase of P - 1
+ phases, nodes in pair communicate their data. MPI barriers are
+ inserted between each two phases.
+
+ * Auther: Ahmad Faraj
+
+ ****************************************************************************/
+int
+smpi_coll_tuned_alltoall_pair_mpi_barrier(void * send_buff, int send_count,
+ MPI_Datatype send_type, void * recv_buff,
+ int recv_count, MPI_Datatype recv_type,
+ MPI_Comm comm)
+{
+ MPI_Status s;
+ MPI_Aint send_chunk, recv_chunk;
+ int i, src, dst, rank, num_procs;
+ int tag = 101, success = 1; /*, failure = 0, pof2 = 1;*/
+ char * send_ptr = (char *) send_buff;
+ char * recv_ptr = (char *) recv_buff;
+
+ MPI_Comm_rank(comm, &rank);
+ MPI_Comm_size(comm, &num_procs);
+ MPI_Type_extent(send_type, &send_chunk);
+ MPI_Type_extent(recv_type, &recv_chunk);
+
+ send_chunk *= send_count;
+ recv_chunk *= recv_count;
+
+ for (i = 0; i < num_procs; i++)
+ {
+ src = dst = rank ^ i;
+ MPI_Barrier(comm);
+ MPI_Sendrecv(send_ptr + dst * send_chunk, send_count, send_type, dst,
+ tag, recv_ptr + src * recv_chunk, recv_count, recv_type,
+ src, tag, comm, &s);
+ }
+ return success;
+}