more precise estimate of costs for splitting pairs.

Former-commit-id: 3a3e0d5d4c6cc076e1e75445d3488f56846e2dc8

src/scheduler.c

@@ -103,6 +103,9 @@ void scheduler_splittasks ( struct scheduler *s ) {
                       { -1 , -1 , -1 , -1 , -1 , 12 , 10 ,  9 } ,
                       { -1 , -1 , -1 , -1 , -1 , -1 , 11 , 10 } ,
                       { -1 , -1 , -1 , -1 , -1 , -1 , -1 , 12 } };
+    float sid_scale[13] = { 0.036f , 0.162f , 0.036f , 0.162f , 0.335f , 0.162f ,
+                            0.036f , 0.162f , 0.036f , 0.162f , 0.335f , 0.162f , 
+                            0.335f };
 
     /* Loop through the tasks... */
     // #pragma omp parallel default(none) shared(s,tid,pts,space_subsize) private(ind,j,k,t,t_old,redo,ci,cj,hi,hj,sid,shift)
@@ -203,7 +206,7 @@ void scheduler_splittasks ( struct scheduler *s ) {
                  
                 /* Replace by a single sub-task? */
                 if ( scheduler_dosub &&
-                     ci->count < space_subsize && cj->count < space_subsize &&
+                     ( ci->count + cj->count ) * sid_scale[sid] < space_subsize &&
                      ci->maxdepth - ci->depth < scheduler_maxsubdepth && cj->maxdepth - cj->depth < scheduler_maxsubdepth &&
                      sid != 0 && sid != 2 && sid != 6 && sid != 8 ) {