Small optimization on the datatype commit.

This patch fixes the merge of contiguous elements into larger but more
compact datatypes, and allows for contiguous elements to have thir
blocklen increasing instead of the count. The idea is to always maximize
the blocklen, aka. the contiguous part of the datatype.

Signed-off-by: George Bosilca <bosilca@icl.utk.edu>
(cherry picked from commit 41e6f55807b01ad5c04e8387a3699cf743931f6a)

opal/datatype/opal_datatype_optimize.c

@@ -163,6 +163,12 @@ opal_datatype_optimize_short( opal_datatype_t* pData,
             if( 0 == last.count ) {  /* first data of the datatype */
                 last = *current;
                 continue;  /* next data */
+            } else {  /* can we merge it in order to decrease count */
+                if( (ptrdiff_t)last.blocklen * (ptrdiff_t)opal_datatype_basicDatatypes[last.common.type]->size == last.extent ) {
+                    last.extent *= last.count;
+                    last.blocklen *= last.count;
+                    last.count = 1;
+                }
             }
 
             /* are the two elements compatible: aka they have very similar values and they
@@ -176,6 +182,16 @@ opal_datatype_optimize_short( opal_datatype_t* pData,
                     last.common.type  = OPAL_DATATYPE_UINT1;
                 }
 
+                if( (last.extent * (ptrdiff_t)last.count + last.disp) == current->disp ) {
+                    if( 1 == current->count ) {
+                        last.count++;
+                        continue;
+                    }
+                    if( last.extent == current->extent ) {
+                        last.count += current->count;
+                        continue;
+                    }
+                }
                 if( 1 == last.count ) {
                     /* we can ignore the extent of the element with count == 1 and merge them together if their displacements match */
                     if( 1 == current->count ) {
@@ -186,17 +202,7 @@ opal_datatype_optimize_short( opal_datatype_t* pData,
                     /* can we compute a matching displacement ? */
                     if( (last.disp + current->extent) == current->disp ) {
                         last.extent = current->extent;
-                        last.count = current->count + 1;
-                        continue;
-                    }
-                }
-                if( (last.extent * (ptrdiff_t)last.count + last.disp) == current->disp ) {
-                    if( 1 == current->count ) {
-                        last.count++;
-                        continue;
-                    }
-                    if( last.extent == current->extent ) {
-                        last.count += current->count;
+                        last.count = current->count + last.count;
                         continue;
                     }
                 }

opal/datatype/opal_datatype_pack.c

@@ -121,6 +121,7 @@ opal_pack_homogeneous_contig_with_gaps_function( opal_convertor_t* pConv,
      * how much we should jump between elements.
      */
     assert( (pData->flags & OPAL_DATATYPE_FLAG_CONTIGUOUS) && ((ptrdiff_t)pData->size != extent) );
+    assert( pData->opt_desc.used <= 1 );
     DO_DEBUG( opal_output( 0, "pack_homogeneous_contig( pBaseBuf %p, iov_count %d )\n",
                            (void*)pConv->pBaseBuf, *out_size ); );
     if( stack[1].type != opal_datatype_uint1.id ) {