From 3cae9f78743d4a3bc83ec311635555270284e9e0 Mon Sep 17 00:00:00 2001
From: Joseph Schuchart <schuchart@hlrs.de>
Date: Wed, 11 Nov 2020 17:58:42 +0100
Subject: [PATCH] COLL TUNED: remove stray selection of linear algs for
 alreduce and allgather

These selections seem harmful in my measurements and don't seem to be
motivated by previous measurement data.

Signed-off-by: Joseph Schuchart <schuchart@icl.utk.edu>
(cherry picked from commit a15e5dc7f042f21f8adc08453b13bc7210bf2bac)
---
 .../coll/tuned/coll_tuned_decision_fixed.c    | 58 +++----------------
 1 file changed, 9 insertions(+), 49 deletions(-)

diff --git a/ompi/mca/coll/tuned/coll_tuned_decision_fixed.c b/ompi/mca/coll/tuned/coll_tuned_decision_fixed.c
index f4d07e568e..c22e71be5b 100644
--- a/ompi/mca/coll/tuned/coll_tuned_decision_fixed.c
+++ b/ompi/mca/coll/tuned/coll_tuned_decision_fixed.c
@@ -92,30 +92,10 @@ ompi_coll_tuned_allreduce_intra_dec_fixed(const void *sbuf, void *rbuf, int coun
             } else {
                 alg = 2;
             }
-        } else if (communicator_size < 32) {
-            alg = 3;
-        } else if (communicator_size < 64) {
-            if (total_dsize < 131072) {
-                alg = 1;
-            } else {
-                alg = 3;
-            }
         } else if (communicator_size < 128) {
-            if (total_dsize < 128) {
-                alg = 1;
-            } else if (total_dsize < 512) {
-                alg = 3;
-            } else if (total_dsize < 8192) {
-                alg = 1;
-            } else {
-                alg = 3;
-            }
+            alg = 3;
         } else if (communicator_size < 256) {
-            if (total_dsize < 2048) {
-                alg = 2;
-            } else if (total_dsize < 16384) {
-                alg = 1;
-            } else if (total_dsize < 131072) {
+            if (total_dsize < 131072) {
                 alg = 2;
             } else if (total_dsize < 524288) {
                 alg = 3;
@@ -183,23 +163,13 @@ ompi_coll_tuned_allreduce_intra_dec_fixed(const void *sbuf, void *rbuf, int coun
                 alg = 6;
             }
         } else if (communicator_size < 128) {
-            if (total_dsize < 128) {
-                alg = 1;
-            } else if (total_dsize < 512) {
-                alg = 3;
-            } else if (total_dsize < 8192) {
-                alg = 1;
-            } else if (total_dsize < 262144) {
+            if (total_dsize < 262144) {
                 alg = 3;
             } else {
                 alg = 6;
             }
         } else if (communicator_size < 256) {
-            if (total_dsize < 2048) {
-                alg = 2;
-            } else if (total_dsize < 16384) {
-                alg = 1;
-            } else if (total_dsize < 131072) {
+            if (total_dsize < 131072) {
                 alg = 2;
             } else if (total_dsize < 262144) {
                 alg = 3;
@@ -1158,9 +1128,7 @@ int ompi_coll_tuned_allgather_intra_dec_fixed(const void *sbuf, int scount,
             alg = 4;
         }
     } else if (communicator_size < 128) {
-        if (total_dsize < 64) {
-            alg = 1;
-        } else if (total_dsize < 512) {
+        if (total_dsize < 512) {
             alg = 3;
         } else if (total_dsize < 65536) {
             alg = 5;
@@ -1168,9 +1136,7 @@ int ompi_coll_tuned_allgather_intra_dec_fixed(const void *sbuf, int scount,
             alg = 4;
         }
     } else if (communicator_size < 256) {
-        if (total_dsize < 32) {
-            alg = 1;
-        } else if (total_dsize < 512) {
+        if (total_dsize < 512) {
             alg = 3;
         } else if (total_dsize < 131072) {
             alg = 5;
@@ -1182,9 +1148,7 @@ int ompi_coll_tuned_allgather_intra_dec_fixed(const void *sbuf, int scount,
             alg = 4;
         }
     } else if (communicator_size < 512) {
-        if (total_dsize < 16) {
-            alg = 1;
-        } else if (total_dsize < 32) {
+        if (total_dsize < 32) {
             alg = 3;
         } else if (total_dsize < 128) {
             alg = 2;
@@ -1200,9 +1164,7 @@ int ompi_coll_tuned_allgather_intra_dec_fixed(const void *sbuf, int scount,
             alg = 4;
         }
     } else if (communicator_size < 1024) {
-        if (total_dsize < 4) {
-            alg = 1;
-        } else if (total_dsize < 64) {
+        if (total_dsize < 64) {
             alg = 3;
         } else if (total_dsize < 256) {
             alg = 2;
@@ -1212,9 +1174,7 @@ int ompi_coll_tuned_allgather_intra_dec_fixed(const void *sbuf, int scount,
             alg = 5;
         }
     } else if (communicator_size < 2048) {
-        if (total_dsize < 2) {
-            alg = 1;
-        } else if (total_dsize < 4) {
+        if (total_dsize < 4) {
             alg = 3;
         } else if (total_dsize < 8) {
             alg = 2;