From dceea5ad87d9a1d131ab295b68d9d400d30e5a7e Mon Sep 17 00:00:00 2001
From: William Zhang <wilzhang@amazon.com>
Date: Tue, 25 Aug 2020 08:41:23 -0700
Subject: [PATCH] coll/tuned: Revert RSB and RS default algorithms

Reduce scatter block and reduce scatter algorithms were hitting
correctness issues for non commutative strided tests. We will revert to
the original default algorithms for those two collectives (basic linear
and non overlapping respectively) in the non commutative op case.

See #8010

Signed-off-by: William Zhang <wilzhang@amazon.com>
(cherry picked from commit 57b95bcb45d5ce3ae1a1e00bd17ceeaa206526fe)
---
 .../coll/tuned/coll_tuned_decision_fixed.c    | 136 +-----------------
 1 file changed, 6 insertions(+), 130 deletions(-)

diff --git a/ompi/mca/coll/tuned/coll_tuned_decision_fixed.c b/ompi/mca/coll/tuned/coll_tuned_decision_fixed.c
index d06f3ea19f..cc73fcf835 100644
--- a/ompi/mca/coll/tuned/coll_tuned_decision_fixed.c
+++ b/ompi/mca/coll/tuned/coll_tuned_decision_fixed.c
@@ -883,64 +883,11 @@ int ompi_coll_tuned_reduce_scatter_intra_dec_fixed( const void *sbuf, void *rbuf
      *  {3, "ring"},
      *  {4, "butterfly"},
      *
-     * Recursive halving and ring do not support non commutative ops.
+     * Non commutative algorithm capability needs re-investigation.
+     * Defaulting to non overlapping for non commutative ops.
      */
     if (!ompi_op_is_commute(op)) {
-        if (communicator_size < 4) {
-            if (total_dsize < 262144) {
-                alg = 4;
-            } else {
-                alg = 1;
-            }
-        } else if (communicator_size < 8) {
-            if (total_dsize < 16) {
-                alg = 1;
-            } else {
-                alg = 4;
-            }
-        } else if (communicator_size < 16) {
-            if (total_dsize < 32) {
-                alg = 1;
-            } else {
-                alg = 4;
-            }
-        } else if (communicator_size < 32) {
-            if (total_dsize < 64) {
-                alg = 1;
-            } else {
-                alg = 4;
-            }
-        } else if (communicator_size < 64) {
-            if (total_dsize < 128) {
-                alg = 1;
-            } else {
-                alg = 4;
-            }
-        } else if (communicator_size < 128) {
-            if (total_dsize < 256) {
-                alg = 1;
-            } else {
-                alg = 4;
-            }
-        } else if (communicator_size < 1024) {
-            if (total_dsize < 512) {
-                alg = 1;
-            } else {
-                alg = 4;
-            }
-        } else if (communicator_size < 2048) {
-            if (total_dsize < 1024) {
-                alg = 1;
-            } else {
-                alg = 4;
-            }
-        } else {
-            if (total_dsize < 2048) {
-                alg = 1;
-            } else {
-                alg = 4;
-            }
-        }
+        alg = 1;
     } else {
         if (communicator_size < 4) {
             if (total_dsize < 65536) {
@@ -1082,82 +1029,11 @@ int ompi_coll_tuned_reduce_scatter_block_intra_dec_fixed(const void *sbuf, void
      *  {3, "recursive_halving"},
      *  {4, "butterfly"},
      *
-     * Only recursive halving does not support non commutative ops.
+     * Non commutative algorithm capability needs re-investigation.
+     * Defaulting to basic linear for non commutative ops.
      */
     if( !ompi_op_is_commute(op) ) {
-        if (communicator_size < 4) {
-            if (total_dsize < 4) {
-                alg = 2;
-            } else if (total_dsize < 131072) {
-                alg = 4;
-            } else {
-                alg = 1;
-            }
-        } else if (communicator_size < 8) {
-            if (total_dsize < 4) {
-                alg = 1;
-            } else if (total_dsize < 32) {
-                alg = 2;
-            } else if (total_dsize < 1048576) {
-                alg = 4;
-            } else {
-                alg = 1;
-            }
-        } else if (communicator_size < 16) {
-            if (total_dsize < 4) {
-                alg = 1;
-            } else if (total_dsize < 524288) {
-                alg = 4;
-            } else if (total_dsize < 4194304) {
-                alg = 1;
-            } else {
-                alg = 4;
-            }
-        } else if (communicator_size < 32) {
-            if (total_dsize < 128) {
-                alg = 1;
-            } else if (total_dsize < 262144) {
-                alg = 4;
-            } else if (total_dsize < 2097152) {
-                alg = 1;
-            } else {
-                alg = 4;
-            }
-        } else if (communicator_size < 64) {
-            if (total_dsize < 64) {
-                alg = 1;
-            } else if (total_dsize < 65536) {
-                alg = 4;
-            } else if (total_dsize < 1048576) {
-                alg = 1;
-            } else {
-                alg = 4;
-            }
-        } else if (communicator_size < 128) {
-            if (total_dsize < 4) {
-                alg = 4;
-            } else if (total_dsize < 64) {
-                alg = 1;
-            } else if (total_dsize < 131072) {
-                alg = 4;
-            } else if (total_dsize < 524288) {
-                alg = 1;
-            } else {
-                alg = 4;
-            }
-        } else {
-            if (total_dsize < 4) {
-                alg = 4;
-            } else if (total_dsize < 16) {
-                alg = 1;
-            } else if (total_dsize < 65536) {
-                alg = 4;
-            } else if (total_dsize < 262144) {
-                alg = 1;
-            } else {
-                alg = 4;
-            }
-        }
+        alg = 1;
     } else {
         if (communicator_size < 4) {
             if (total_dsize < 4) {