Avoid a needless locking in sp_search()
authorMarco Costalba <mcostalba@gmail.com>
Mon, 19 Oct 2009 06:44:06 +0000 (07:44 +0100)
committerMarco Costalba <mcostalba@gmail.com>
Mon, 19 Oct 2009 06:47:18 +0000 (07:47 +0100)
Only in less then 2% of cases we have a new sp->bestValue,
so check before to lock and save a costly locking
most of the times.

Patch suggested by Joona.

No functional search.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
src/search.cpp

index 13affe1b2f06e0a30fd95b5ea5548aad61c3c524..ec4272a9e0f9bcb7ebf601515621e34be4e632ba 100644 (file)
@@ -1759,21 +1759,24 @@ namespace {
           break;
 
       // New best move?
-      lock_grab(&(sp->lock));
-      if (value > sp->bestValue && !thread_should_stop(threadID))
+      if (value > sp->bestValue) // Less then 2% of cases
       {
-          sp->bestValue = value;
-          if (sp->bestValue >= sp->beta)
+          lock_grab(&(sp->lock));
+          if (value > sp->bestValue && !thread_should_stop(threadID))
           {
-              sp_update_pv(sp->parentSstack, ss, sp->ply);
-              for (int i = 0; i < ActiveThreads; i++)
-                  if (i != threadID && (i == sp->master || sp->slaves[i]))
-                      Threads[i].stop = true;
+              sp->bestValue = value;
+              if (sp->bestValue >= sp->beta)
+              {
+                  sp_update_pv(sp->parentSstack, ss, sp->ply);
+                  for (int i = 0; i < ActiveThreads; i++)
+                      if (i != threadID && (i == sp->master || sp->slaves[i]))
+                          Threads[i].stop = true;
 
-              sp->finished = true;
-        }
+                  sp->finished = true;
+              }
+          }
+          lock_release(&(sp->lock));
       }
-      lock_release(&(sp->lock));
     }
 
     lock_grab(&(sp->lock));