Implement 'old' multipv search.

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 2fd842070cfe2720217eb6f8876aa02ba61075a7..f47507f7e39b6ad6ba7a7ffaf3ebe2f17e1cd6e0 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -67,8 +67,7 @@ namespace {
   const int skipPhase[] = { 0, 1, 0, 1, 2, 3, 0, 1, 2, 3, 4, 5, 0, 1, 2, 3, 4, 5, 6, 7 };
 
   // Razoring and futility margin based on depth
-  // razor_margin[0] is unused as long as depth >= ONE_PLY in search
-  const int razor_margin[] = { 0, 570, 603, 554 };
+  const int razor_margin = 600;
   Value futility_margin(Depth d) { return Value(150 * d / ONE_PLY); }
 
   // Futility and reductions lookup tables, initialized at startup
@@ -298,7 +297,7 @@ void Thread::search() {
       mainThread->bestMoveChanges = 0;
   }
 
-  size_t multiPV = Options["MultiPV"];
+  multiPV = Options["MultiPV"];
   Skill skill(Options["Skill Level"]);
 
   // When playing with strength handicap enable MultiPV search that we will
@@ -500,7 +499,7 @@ namespace {
     Key posKey;
     Move ttMove, move, excludedMove, bestMove;
     Depth extension, newDepth;
-    Value bestValue, value, ttValue, eval;
+    Value bestValue, value, ttValue, eval, maxValue;
     bool ttHit, inCheck, givesCheck, singularExtensionNode, improving;
     bool captureOrPromotion, doFullDepthSearch, moveCountPruning, skipQuiets, ttCapture, pvExact;
     Piece movedPiece;
@@ -512,6 +511,7 @@ namespace {
     moveCount = captureCount = quietCount = ss->moveCount = 0;
     ss->statScore = 0;
     bestValue = -VALUE_INFINITE;
+    maxValue = VALUE_INFINITE;
 
     // Check for the available remaining time
     if (thisThread == Threads.main())
@@ -599,7 +599,7 @@ namespace {
             && !pos.can_castle(ANY_CASTLING))
         {
             TB::ProbeState err;
-            TB::WDLScore v = Tablebases::probe_wdl(pos, &err);
+            TB::WDLScore wdl = Tablebases::probe_wdl(pos, &err);
 
             if (err != TB::ProbeState::FAIL)
             {
@@ -607,15 +607,30 @@ namespace {
 
                 int drawScore = TB::UseRule50 ? 1 : 0;
 
-                value =  v < -drawScore ? -VALUE_MATE + MAX_PLY + ss->ply + 1
-                       : v >  drawScore ?  VALUE_MATE - MAX_PLY - ss->ply - 1
-                                        :  VALUE_DRAW + 2 * v * drawScore;
+                value =  wdl < -drawScore ? -VALUE_MATE + MAX_PLY + ss->ply + 1
+                       : wdl >  drawScore ?  VALUE_MATE - MAX_PLY - ss->ply - 1
+                                          :  VALUE_DRAW + 2 * wdl * drawScore;
 
-                tte->save(posKey, value_to_tt(value, ss->ply), BOUND_EXACT,
-                          std::min(DEPTH_MAX - ONE_PLY, depth + 6 * ONE_PLY),
-                          MOVE_NONE, VALUE_NONE, TT.generation());
+                Bound b =  wdl < -drawScore ? BOUND_UPPER
+                         : wdl >  drawScore ? BOUND_LOWER : BOUND_EXACT;
 
-                return value;
+                if (    b == BOUND_EXACT
+                    || (b == BOUND_LOWER ? value >= beta : value <= alpha))
+                {
+                    tte->save(posKey, value_to_tt(value, ss->ply), b,
+                              std::min(DEPTH_MAX - ONE_PLY, depth + 6 * ONE_PLY),
+                              MOVE_NONE, VALUE_NONE, TT.generation());
+
+                    return value;
+                }
+
+                if (PvNode)
+                {
+                    if (b == BOUND_LOWER)
+                        bestValue = value, alpha = std::max(alpha, bestValue);
+                    else
+                        maxValue = value;
+                }
             }
         }
     }
@@ -654,12 +669,12 @@ namespace {
     // Step 6. Razoring (skipped when in check)
     if (   !PvNode
         &&  depth < 4 * ONE_PLY
-        &&  eval + razor_margin[depth / ONE_PLY] <= alpha)
+        &&  eval + razor_margin <= alpha)
     {
         if (depth <= ONE_PLY)
             return qsearch<NonPV, false>(pos, ss, alpha, alpha+1);
 
-        Value ralpha = alpha - razor_margin[depth / ONE_PLY];
+        Value ralpha = alpha - razor_margin;
         Value v = qsearch<NonPV, false>(pos, ss, ralpha, ralpha+1);
         if (v <= ralpha)
             return v;
@@ -787,12 +802,20 @@ moves_loop: // When in check search starts from here
       if (move == excludedMove)
           continue;
 
-      // At root obey the "searchmoves" option and skip moves not listed in Root
-      // Move List. As a consequence any illegal move is also skipped. In MultiPV
-      // mode we also skip PV moves which have been already searched.
-      if (rootNode && !std::count(thisThread->rootMoves.begin() + thisThread->PVIdx,
-                                  thisThread->rootMoves.end(), move))
-          continue;
+      if (rootNode)
+      {
+          // At root obey the "searchmoves" option and skip moves not listed in Root
+          // Move List. As a consequence any illegal move is also skipped.
+          if (!std::count(thisThread->rootMoves.begin() + thisThread->PVIdx,
+                          thisThread->rootMoves.end(), move))
+              continue;
+
+          // In MultiPV mode we not only skip PV moves which have already been searched,
+          // but also any other move except we have reached the last PV line.
+          if (   thisThread->PVIdx + 1 < thisThread->multiPV
+              && move != ttMove)
+              continue;
+      }
 
       ss->moveCount = ++moveCount;
 
@@ -1092,6 +1115,9 @@ moves_loop: // When in check search starts from here
              && is_ok((ss-1)->currentMove))
         update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth));
 
+    if (PvNode)
+        bestValue = std::min(bestValue, maxValue);
+
     if (!excludedMove)
         tte->save(posKey, value_to_tt(bestValue, ss->ply),
                   bestValue >= beta ? BOUND_LOWER :
@@ -1252,7 +1278,6 @@ moves_loop: // When in check search starts from here
 
       // Don't search moves with negative SEE values
       if (  (!InCheck || evasionPrunable)
-          &&  type_of(move) != PROMOTION
           &&  !pos.see_ge(move))
           continue;
 
@@ -1510,7 +1535,7 @@ string UCI::pv(const Position& pos, Depth depth, Value alpha, Value beta) {
   int elapsed = Time.elapsed() + 1;
   const RootMoves& rootMoves = pos.this_thread()->rootMoves;
   size_t PVIdx = pos.this_thread()->PVIdx;
-  size_t multiPV = std::min((size_t)Options["MultiPV"], rootMoves.size());
+  size_t multiPV = pos.this_thread()->multiPV;
   uint64_t nodesSearched = Threads.nodes_searched();
   uint64_t tbHits = Threads.tb_hits() + (TB::RootInTB ? rootMoves.size() : 0);
 
@@ -1628,4 +1653,9 @@ void Tablebases::filter_root_moves(Position& pos, Search::RootMoves& rootMoves)
         TB::Score =  TB::Score > VALUE_DRAW ?  VALUE_MATE - MAX_PLY - 1
                    : TB::Score < VALUE_DRAW ? -VALUE_MATE + MAX_PLY + 1
                                             :  VALUE_DRAW;
+
+    // Since root_probe() and root_probe_wdl() dirty the root move scores,
+    // we reset them to -VALUE_INFINITE
+    for (RootMove& rm : rootMoves)
+        rm.score = -VALUE_INFINITE;
 }