Updated broadcast decision function based on MX results up to 64 nodes.

(The previous decision function did not consider binomial algorithm (since we did not have it at the time)).

This commit was SVN r13007.

ompi/mca/coll/tuned/coll_tuned_decision_fixed.c

@@ -166,12 +166,17 @@ int ompi_coll_tuned_bcast_intra_dec_fixed(void *buff, int count,
                                           struct ompi_datatype_t *datatype, int root,
                                           struct ompi_communicator_t *comm)
 {
-    const double a0 = -7.8710;
-    const double b0 = 41.1613;
-    const double a1 = 0.0150;
-    const double b1 = 11.2445;
-    const double a2 = 0.0023;
-    const double b2 = 3.8074;
+    /* Decision function based on MX results for 
+    messages up to 36MB and communicator sizes up to 64 nodes */
+    const double small_message_size = 2048;
+    const double intermediate_message_size = 370728;
+    const double a_p16  = 3.2118e-6; /* [1 / byte] */
+    const double b_p16  = 8.7936;   
+    const double a_p64  = 2.3679e-6; /* [1 / byte] */
+    const double b_p64  = 1.1787;     
+    const double a_p128 = 1.6134e-6; /* [1 / byte] */
+    const double b_p128 = 2.1102;
+
     int communicator_size, rank;
     int segsize = 0;
     size_t message_size, dsize;
@@ -183,47 +188,54 @@ int ompi_coll_tuned_bcast_intra_dec_fixed(void *buff, int count,
     ompi_ddt_type_size(datatype, &dsize);
     message_size = dsize * (unsigned long)count;   /* needed for decision */
 
-    OPAL_OUTPUT((ompi_coll_tuned_stream,"ompi_coll_tuned_bcast_intra_dec_fixed "
-                 "root %d rank %d com_size %d msg_length %ld",
+    OPAL_OUTPUT((ompi_coll_tuned_stream, "ompi_coll_tuned_bcast_intra_dec_fixed root %d rank %d com_size %d msg_length %ld",
                  root, rank, communicator_size, message_size));
 
-    if ((message_size <= 1024) && (communicator_size < 12)) {
-        /* Linear_0K */
-        return ompi_coll_tuned_bcast_intra_basic_linear (buff, count, datatype, root, comm);
-    } else if (message_size < 8192) {
-        if ((communicator_size < 12) || 
-            (communicator_size < (a0 * (message_size / 1024.0) + b0))) {
-            /* Binary_0K */
-            segsize = 0;
-        } else {
-            /* Binary_1K */
-            segsize = 1024;
-        }
-        return  ompi_coll_tuned_bcast_intra_bintree (buff, count, datatype, root, comm, segsize);
-    } else if (message_size <= 35000) {
-        if (communicator_size <= 12) {
-            /* Binary_8K */
-            segsize = 1024 << 3;
-            return  ompi_coll_tuned_bcast_intra_bintree (buff, count, datatype, root, comm, segsize);
-        } else {
-            /* SplittedBinary_1K */
-            segsize = 1024;
-            return ompi_coll_tuned_bcast_intra_split_bintree(buff, count, datatype, root, comm, segsize);
-        }
+    /* Handle messages of small and intermediate size */
+    if (message_size < small_message_size) {
+       /* Binomial without segmentation */
+       segsize = 0;
+       return  ompi_coll_tuned_bcast_intra_binomial (buff, count, datatype, 
+						     root, comm, segsize);
+
+    } else if (message_size < intermediate_message_size) {
+       /* SplittedBinary with 1KB segments */
+       segsize = 1024;
+       return ompi_coll_tuned_bcast_intra_split_bintree(buff, count, datatype, 
+							root, comm, segsize);
+
+    } 
+    /* Handle large message sizes */
+    else if (communicator_size < (a_p128 * message_size + b_p128)) {
+       /* Pipeline with 128KB segments */
+       segsize = 1024  << 7;
+       return ompi_coll_tuned_bcast_intra_pipeline (buff, count, datatype, 
+						    root, comm, segsize);
+
+    } else if (communicator_size < 13) {
+       /* Split Binary with 8KB segments */
+       segsize = 1024 << 3;
+       return ompi_coll_tuned_bcast_intra_split_bintree(buff, count, datatype, 
+							root, comm, segsize);
+       
+    } else if (communicator_size < (a_p64 * message_size + b_p64)) {
+       /* Pipeline with 64KB segments */
+       segsize = 1024 << 6;
+       return ompi_coll_tuned_bcast_intra_pipeline (buff, count, datatype, 
+						    root, comm, segsize);
+
+    } else if (communicator_size < (a_p16 * message_size + b_p16)) {
+       /* Pipeline with 16KB segments */
+       segsize = 1024 << 4;
+       return ompi_coll_tuned_bcast_intra_pipeline (buff, count, datatype, 
+						    root, comm, segsize);
 
-    } else if (communicator_size > (a1 * (message_size / 1024.0) + b1)) {
-        /* SplittedBinary_8K */
-        segsize = 1024 << 3;
-        return ompi_coll_tuned_bcast_intra_split_bintree(buff, count, datatype, root, comm, segsize);
     }
-    if (communicator_size > (a2 * (message_size / 1024.0) + b2)) {
-        /* Pipeline_8K */
-        segsize = 1024 << 3;
-    } else {
-        /* Pipeline_64K */
-        segsize = 1024 << 6;
-    }
-    return ompi_coll_tuned_bcast_intra_pipeline (buff, count, datatype, root, comm, segsize);
+
+    /* Pipeline with 8KB segments */
+    segsize = 1024 << 3;
+    return ompi_coll_tuned_bcast_intra_pipeline (buff, count, datatype, 
+						 root, comm, segsize);
 #if 0
     /* this is based on gige measurements */