Use rml[0].pv[] instead of dedicated pv[] array

We have a small functionality change in case we have a
fail-high so that both rml[].pv and pv[] are updated, but if,
after researching, we have a fail-low then rml score is updated
again but pv[] remains the same and coming back from search we
used a PV line that has failed-low (after having failed-high).

With this patch we always use the 'correct' PV line, i.e. the
line with highest score at the end of the whole search.

Retire also redundant RootMove's 'move' member and directly
use pv[0] instead.

diff --git a/src/search.cpp b/src/search.cpp
index b75b6fa850f7d359d269faeac62b58258c55b3c2..fceaccb524fec10493a68961222ccd7a225e49d8 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -124,14 +124,12 @@ namespace {
     // way we are guaranteed that PV moves are always sorted as first.
     bool operator<(const RootMove& m) const {
       return pv_score != m.pv_score ? pv_score < m.pv_score
-                                    : non_pv_score <= m.non_pv_score;
+                                    : non_pv_score < m.non_pv_score;
     }
-    void set_pv(const Move newPv[]);
 
     int64_t nodes;
     Value pv_score;
     Value non_pv_score;
-    Move move;
     Move pv[PLY_MAX_PLUS_2];
   };
 
@@ -139,26 +137,23 @@ namespace {
 
     nodes = 0;
     pv_score = non_pv_score = -VALUE_INFINITE;
-    move = pv[0] = MOVE_NONE;
+    pv[0] = MOVE_NONE;
   }
 
   RootMove& RootMove::operator=(const RootMove& rm) {
 
+    const Move* src = rm.pv;
+    Move* dst = pv;
+
+    // Avoid a costly full rm.pv[] copy
+    do *dst++ = *src; while (*src++ != MOVE_NONE);
+
     nodes = rm.nodes;
     pv_score = rm.pv_score;
     non_pv_score = rm.non_pv_score;
-    move = rm.move;
-    set_pv(rm.pv); // Skip costly full pv[] copy
     return *this;
   }
 
-  void RootMove::set_pv(const Move newPv[]) {
-
-    Move* p = pv;
-
-    do *p++ = *newPv; while (*newPv++ != MOVE_NONE);
-  }
-
 
   // RootMoveList struct is essentially a std::vector<> of RootMove objects,
   // with an handful of methods above the standard ones.
@@ -298,7 +293,7 @@ namespace {
   /// Local functions
 
   Value id_loop(Position& pos, Move searchMoves[]);
-  Value root_search(Position& pos, SearchStack* ss, Move* pv, RootMoveList& rml, Value* alphaPtr, Value* betaPtr);
+  Value root_search(Position& pos, SearchStack* ss, RootMoveList& rml, Value* alphaPtr, Value* betaPtr);
 
   template <NodeType PvNode, bool SpNode>
   Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply);
@@ -538,7 +533,6 @@ namespace {
   Value id_loop(Position& pos, Move searchMoves[]) {
 
     SearchStack ss[PLY_MAX_PLUS_2];
-    Move pv[PLY_MAX_PLUS_2];
     Move EasyMove = MOVE_NONE;
     Value value, alpha = -VALUE_INFINITE, beta = VALUE_INFINITE;
 
@@ -563,20 +557,19 @@ namespace {
          << " time " << current_search_time()
          << " nodes " << pos.nodes_searched()
          << " nps " << nps(pos)
-         << " pv " << rml[0].move << "\n";
+         << " pv " << rml[0].pv[0] << "\n";
 
     // Initialize
     TT.new_search();
     H.clear();
     init_ss_array(ss, PLY_MAX_PLUS_2);
-    pv[0] = pv[1] = MOVE_NONE;
     ValueByIteration[1] = rml[0].pv_score;
     Iteration = 1;
 
     // Is one move significantly better than others after initial scoring ?
     if (   rml.size() == 1
         || rml[0].pv_score > rml[1].pv_score + EasyMoveMargin)
-        EasyMove = rml[0].move;
+        EasyMove = rml[0].pv[0];
 
     // Iterative deepening loop
     while (Iteration < PLY_MAX)
@@ -601,11 +594,7 @@ namespace {
         }
 
         // Search to the current depth, rml is updated and sorted, alpha and beta could change
-        value = root_search(pos, ss, pv, rml, &alpha, &beta);
-
-        // Write PV to transposition table, in case the relevant entries have
-        // been overwritten during the search.
-        insert_pv_in_tt(pos, pv);
+        value = root_search(pos, ss, rml, &alpha, &beta);
 
         if (AbortSearch)
             break; // Value cannot be trusted. Break out immediately!
@@ -614,7 +603,7 @@ namespace {
         ValueByIteration[Iteration] = value;
 
         // Drop the easy move if differs from the new best move
-        if (pv[0] != EasyMove)
+        if (rml[0].pv[0] != EasyMove)
             EasyMove = MOVE_NONE;
 
         if (UseTimeManagement)
@@ -635,7 +624,7 @@ namespace {
 
             // Stop search early if one move seems to be much better than the others
             if (   Iteration >= 8
-                && EasyMove == pv[0]
+                && EasyMove == rml[0].pv[0]
                 && (  (   rml[0].nodes > (pos.nodes_searched() * 85) / 100
                        && current_search_time() > TimeMgr.available_time() / 16)
                     ||(   rml[0].nodes > (pos.nodes_searched() * 98) / 100
@@ -677,18 +666,10 @@ namespace {
              << " time " << current_search_time() << endl;
 
     // Print the best move and the ponder move to the standard output
-    if (pv[0] == MOVE_NONE || MultiPV > 1)
-    {
-        pv[0] = rml[0].move;
-        pv[1] = MOVE_NONE;
-    }
+    cout << "bestmove " << rml[0].pv[0];
 
-    assert(pv[0] != MOVE_NONE);
-
-    cout << "bestmove " << pv[0];
-
-    if (pv[1] != MOVE_NONE)
-        cout << " ponder " << pv[1];
+    if (rml[0].pv[1] != MOVE_NONE)
+        cout << " ponder " << rml[0].pv[1];
 
     cout << endl;
 
@@ -702,12 +683,12 @@ namespace {
 
         LogFile << "\nNodes: " << pos.nodes_searched()
                 << "\nNodes/second: " << nps(pos)
-                << "\nBest move: " << move_to_san(pos, pv[0]);
+                << "\nBest move: " << move_to_san(pos, rml[0].pv[0]);
 
         StateInfo st;
-        pos.do_move(pv[0], st);
+        pos.do_move(rml[0].pv[0], st);
         LogFile << "\nPonder move: "
-                << move_to_san(pos, pv[1]) // Works also with MOVE_NONE
+                << move_to_san(pos, rml[0].pv[1]) // Works also with MOVE_NONE
                 << endl;
     }
     return rml[0].pv_score;
@@ -719,7 +700,7 @@ namespace {
   // scheme, prints some information to the standard output and handles
   // the fail low/high loops.
 
-  Value root_search(Position& pos, SearchStack* ss, Move* pv, RootMoveList& rml, Value* alphaPtr, Value* betaPtr) {
+  Value root_search(Position& pos, SearchStack* ss, RootMoveList& rml, Value* alphaPtr, Value* betaPtr) {
 
     StateInfo st;
     CheckInfo ci(pos);
@@ -773,7 +754,7 @@ namespace {
 
             // Pick the next root move, and print the move and the move number to
             // the standard output.
-            move = ss->currentMove = rml[i].move;
+            move = ss->currentMove = rml[i].pv[0];
 
             if (current_search_time() >= 1000)
                 cout << "info currmove " << move
@@ -857,11 +838,10 @@ namespace {
                 // the score before research in case we run out of time while researching.
                 rml[i].pv_score = value;
                 ss->bestMove = move;
-                extract_pv_from_tt(pos, move, pv);
-                rml[i].set_pv(pv);
+                extract_pv_from_tt(pos, move, rml[i].pv);
 
                 // Print information to the standard output
-                print_pv_info(pos, pv, alpha, beta, value);
+                print_pv_info(pos, rml[i].pv, alpha, beta, value);
 
                 // Prepare for a research after a fail high, each time with a wider window
                 *betaPtr = beta = Min(beta + AspirationDelta * (1 << researchCountFH), VALUE_INFINITE);
@@ -893,8 +873,7 @@ namespace {
                 // Update PV
                 rml[i].pv_score = value;
                 ss->bestMove = move;
-                extract_pv_from_tt(pos, move, pv);
-                rml[i].set_pv(pv);
+                extract_pv_from_tt(pos, move, rml[i].pv);
 
                 if (MultiPV == 1)
                 {
@@ -905,7 +884,7 @@ namespace {
                         BestMoveChangesByIteration[Iteration]++;
 
                     // Print information to the standard output
-                    print_pv_info(pos, pv, alpha, beta, value);
+                    print_pv_info(pos, rml[i].pv, alpha, beta, value);
 
                     // Raise alpha to setup proper non-pv search upper bound
                     if (value > alpha)
@@ -954,6 +933,10 @@ namespace {
     // Sort the moves before to return
     rml.sort();
 
+    // Write PV to transposition table, in case the relevant entries have
+    // been overwritten during the search.
+    insert_pv_in_tt(pos, rml[0].pv);
+
     return alpha;
   }
 
@@ -2687,7 +2670,7 @@ split_point_start: // At split points actual search starts from here
         pos.do_move(cur->move, st);
 
         RootMove rm;
-        rm.move = ss[0].currentMove = rm.pv[0] = cur->move;
+        rm.pv[0] = ss[0].currentMove = cur->move;
         rm.pv[1] = MOVE_NONE;
         rm.pv_score = -qsearch<PV>(pos, ss+1, -VALUE_INFINITE, VALUE_INFINITE, DEPTH_ZERO, 1);
         push_back(rm);
@@ -2710,7 +2693,7 @@ split_point_start: // At split points actual search starts from here
 
       while ((move = mp.get_next_move()) != MOVE_NONE)
           for (Base::iterator it = begin(); it != end(); ++it)
-              if (it->move == move)
+              if (it->pv[0] == move)
               {
                   it->non_pv_score = score--;
                   break;