Temporary restore old sp_search()

There is a bug in the conversion that is triggered when testing
with faked split and that I missed somehow :-(

To allow proper testing on cluster restore old sp_search()
until I don't fiugre up what's happened.

Restored to be functional equivalent to old behaviour both in
single thread and in faked split.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>

diff --git a/src/search.cpp b/src/search.cpp
index 13a0175aae57a728c0f8d3635da1be34ba1d795d..00fa04dd44a8408258b3261a7b71402a6f4781a7 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -284,6 +284,9 @@ namespace {
       return search<PvNode, false>(pos, ss, alpha, beta, depth, ply);
   }
 
+  template <NodeType PvNode>
+  void sp_search(Position& pos, SearchStack* ss, Value, Value beta, Depth depth, int ply);
+
   template <NodeType PvNode>
   Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply);
 
@@ -1364,24 +1367,29 @@ split_point_start: // At split points actual search starts from here
       if (value > bestValue && !(SpNode && ThreadsMgr.thread_should_stop(threadID)))
       {
           bestValue = value;
+
+          if (SpNode)
+              sp->bestValue = value;
+
           if (value > alpha)
           {
               if (SpNode && (!PvNode || value >= beta))
                   sp->stopRequest = true;
 
               if (PvNode && value < beta) // We want always alpha < beta
+              {
                   alpha = value;
+                  if (SpNode)
+                      sp->alpha = value;
+              }
 
               if (value == value_mate_in(ply + 1))
                   ss->mateKiller = move;
 
               ss->bestMove = move;
-          }
-          if (SpNode)
-          {
-              sp->bestValue = bestValue;
-              sp->alpha = alpha;
-              sp->parentSstack->bestMove = ss->bestMove;
+
+              if (SpNode)
+                  sp->parentSstack->bestMove = move;
           }
       }
 
@@ -1607,6 +1615,172 @@ split_point_start: // At split points actual search starts from here
   }
 
 
+  // sp_search() is used to search from a split point.  This function is called
+  // by each thread working at the split point.  It is similar to the normal
+  // search() function, but simpler.  Because we have already probed the hash
+  // table, done a null move search, and searched the first move before
+  // splitting, we don't have to repeat all this work in sp_search().  We
+  // also don't need to store anything to the hash table here:  This is taken
+  // care of after we return from the split point.
+
+  template <NodeType PvNode>
+  void sp_search(Position& pos, SearchStack* ss, Value, Value beta, Depth depth, int ply) {
+
+    StateInfo st;
+    Move move;
+    Depth ext, newDepth;
+    Value value;
+    Value futilityValueScaled; // NonPV specific
+    bool isCheck, moveIsCheck, captureOrPromotion, dangerous;
+    int moveCount;
+    value = -VALUE_INFINITE;
+    SplitPoint* sp = ss->sp;
+    Move threatMove = sp->threatMove;
+    MovePicker& mp = *sp->mp;
+    int threadID = pos.thread();
+
+    CheckInfo ci(pos);
+    isCheck = pos.is_check();
+
+    // Step 10. Loop through moves
+    // Loop through all legal moves until no moves remain or a beta cutoff occurs
+    lock_grab(&(sp->lock));
+
+    while (    sp->bestValue < beta
+           && (move = mp.get_next_move()) != MOVE_NONE
+           && !ThreadsMgr.thread_should_stop(threadID))
+    {
+      moveCount = ++sp->moveCount;
+      lock_release(&(sp->lock));
+
+      assert(move_is_ok(move));
+
+      moveIsCheck = pos.move_is_check(move, ci);
+      captureOrPromotion = pos.move_is_capture_or_promotion(move);
+
+      // Step 11. Decide the new search depth
+      ext = extension<PvNode>(pos, move, captureOrPromotion, moveIsCheck, false, sp->mateThreat, &dangerous);
+      newDepth = depth - ONE_PLY + ext;
+
+      // Update current move
+      ss->currentMove = move;
+
+      // Step 12. Futility pruning (is omitted in PV nodes)
+      if (   !PvNode
+          && !captureOrPromotion
+          && !isCheck
+          && !dangerous
+          && !move_is_castle(move))
+      {
+          // Move count based pruning
+          if (   moveCount >= futility_move_count(depth)
+              && !(threatMove && connected_threat(pos, move, threatMove))
+              && sp->bestValue > value_mated_in(PLY_MAX))
+          {
+              lock_grab(&(sp->lock));
+              continue;
+          }
+
+          // Value based pruning
+          Depth predictedDepth = newDepth - reduction<NonPV>(depth, moveCount);
+          futilityValueScaled =  ss->eval + futility_margin(predictedDepth, moveCount)
+                               + H.gain(pos.piece_on(move_from(move)), move_to(move));
+
+          if (futilityValueScaled < beta)
+          {
+              lock_grab(&(sp->lock));
+
+              if (futilityValueScaled > sp->bestValue)
+                  sp->bestValue = futilityValueScaled;
+              continue;
+          }
+      }
+
+      // Step 13. Make the move
+      pos.do_move(move, st, ci, moveIsCheck);
+
+      // Step 14. Reduced search
+      // If the move fails high will be re-searched at full depth.
+      bool doFullDepthSearch = true;
+
+      if (   !captureOrPromotion
+          && !dangerous
+          && !move_is_castle(move)
+          && !(ss->killers[0] == move || ss->killers[1] == move))
+      {
+          ss->reduction = reduction<PvNode>(depth, moveCount);
+          if (ss->reduction)
+          {
+              Value localAlpha = sp->alpha;
+              Depth d = newDepth - ss->reduction;
+              value = d < ONE_PLY ? -qsearch<NonPV>(pos, ss+1, -(localAlpha+1), -localAlpha, DEPTH_ZERO, ply+1)
+                                  : - search<NonPV>(pos, ss+1, -(localAlpha+1), -localAlpha, d, ply+1);
+
+              doFullDepthSearch = (value > localAlpha);
+          }
+
+          // The move failed high, but if reduction is very big we could
+          // face a false positive, retry with a less aggressive reduction,
+          // if the move fails high again then go with full depth search.
+          if (doFullDepthSearch && ss->reduction > 2 * ONE_PLY)
+          {
+              assert(newDepth - ONE_PLY >= ONE_PLY);
+
+              ss->reduction = ONE_PLY;
+              Value localAlpha = sp->alpha;
+              value = -search<NonPV>(pos, ss+1, -(localAlpha+1), -localAlpha, newDepth-ss->reduction, ply+1);
+              doFullDepthSearch = (value > localAlpha);
+          }
+          ss->reduction = DEPTH_ZERO; // Restore original reduction
+      }
+
+      // Step 15. Full depth search
+      if (doFullDepthSearch)
+      {
+          Value localAlpha = sp->alpha;
+          value = newDepth < ONE_PLY ? -qsearch<NonPV>(pos, ss+1, -(localAlpha+1), -localAlpha, DEPTH_ZERO, ply+1)
+                                     : - search<NonPV>(pos, ss+1, -(localAlpha+1), -localAlpha, newDepth, ply+1);
+
+          // Step extra. pv search (only in PV nodes)
+          // Search only for possible new PV nodes, if instead value >= beta then
+          // parent node fails low with value <= alpha and tries another move.
+          if (PvNode && value > localAlpha && value < beta)
+              value = newDepth < ONE_PLY ? -qsearch<PV>(pos, ss+1, -beta, -sp->alpha, DEPTH_ZERO, ply+1)
+                                         : - search<PV>(pos, ss+1, -beta, -sp->alpha, newDepth, ply+1);
+      }
+
+      // Step 16. Undo move
+      pos.undo_move(move);
+
+      assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
+
+      // Step 17. Check for new best move
+      lock_grab(&(sp->lock));
+
+      if (value > sp->bestValue && !ThreadsMgr.thread_should_stop(threadID))
+      {
+          sp->bestValue = value;
+          if (value > sp->alpha)
+          {
+              if (!PvNode || value >= beta)
+                  sp->stopRequest = true;
+
+              if (PvNode && value < beta) // We want always sp->alpha < beta
+                  sp->alpha = value;
+
+              sp->parentSstack->bestMove = ss->bestMove = move;
+          }
+      }
+    }
+
+    /* Here we have the lock still grabbed */
+
+    sp->slaves[threadID] = 0;
+
+    lock_release(&(sp->lock));
+  }
+
+
   // connected_moves() tests whether two moves are 'connected' in the sense
   // that the first move somehow made the second move possible (for instance
   // if the moving piece is the same in both moves). The first move is assumed
@@ -2258,9 +2432,11 @@ split_point_start: // At split points actual search starts from here
             ss->sp = tsp;
 
             if (tsp->pvNode)
-                search<PV, true>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
+                //search<PV, true>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
+                sp_search<PV>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
             else
-                search<NonPV, true>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
+                //search<NonPV, true>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
+                sp_search<NonPV>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
 
             assert(threads[threadID].state == THREAD_SEARCHING);