From 7b4a82f53216492d4eefe355fc4347e46336bf8c Mon Sep 17 00:00:00 2001 From: Augustin Degomme Date: Thu, 11 Sep 2014 10:55:48 +0200 Subject: [PATCH] update algo --- src/smpi/colls/alltoallv-ring.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/src/smpi/colls/alltoallv-ring.c b/src/smpi/colls/alltoallv-ring.c index 4e48add2eb..3f2ced2ab7 100644 --- a/src/smpi/colls/alltoallv-ring.c +++ b/src/smpi/colls/alltoallv-ring.c @@ -44,14 +44,21 @@ smpi_coll_tuned_alltoallv_ring(void *send_buff, int *send_counts, int *send_disp num_procs = smpi_comm_size(comm); send_chunk = smpi_datatype_get_extent(send_type); recv_chunk = smpi_datatype_get_extent(recv_type); - + int pof2 = ((num_procs != 0) && ((num_procs & (~num_procs + 1)) == num_procs)); for (i = 0; i < num_procs; i++) { - src = (rank - i + num_procs) % num_procs; - dst = (rank + i) % num_procs; + + if (pof2 == 1) { + /* use exclusive-or algorithm */ + src = dst = rank ^ i; + } else { + src = (rank - i + num_procs) % num_procs; + dst = (rank + i) % num_procs; + } smpi_mpi_sendrecv(send_ptr + send_disps[dst] * send_chunk, send_counts[dst], send_type, dst, tag, recv_ptr + recv_disps[src] * recv_chunk, recv_counts[src], recv_type, src, tag, comm, &s); + } return MPI_SUCCESS; } -- 2.20.1