Explicitly pass RootMoves to TB probes

Currently Search::RootMoves is accessed and even
modified by TB probing functions in a hidden
and sneaky way.

This is bad practice and makes the code tricky.
Instead explicily pass the vector as function
argument so to clarify that the vector is modified
inside the functions.

No functional change.

src/search.cpp

@@ -39,7 +39,7 @@ namespace Search {
 
   volatile SignalsType Signals;
   LimitsType Limits;
-  std::vector<RootMove> RootMoves;
+  RootMoveVector RootMoves;
   Position RootPos;
   Time::point SearchTime;
   StateStackPtr SetupStates;
@@ -206,9 +206,9 @@ void Search::think() {
   TB::Cardinality = Options["SyzygyProbeLimit"];
 
   // Skip TB probing when no TB found: !TBLargest -> !TB::Cardinality
-  if (TB::Cardinality > TB::TBLargest)
+  if (TB::Cardinality > TB::MaxCardinality)
   {
-      TB::Cardinality = TB::TBLargest;
+      TB::Cardinality = TB::MaxCardinality;
       TB::ProbeDepth = DEPTH_ZERO;
   }
 
@@ -226,15 +226,15 @@ void Search::think() {
       {
           // If the current root position is in the tablebases then RootMoves
           // contains only moves that preserve the draw or win.
-          TB::RootInTB = Tablebases::root_probe(RootPos, TB::Score);
+          TB::RootInTB = Tablebases::root_probe(RootPos, RootMoves, TB::Score);
 
           if (TB::RootInTB)
               TB::Cardinality = 0; // Do not probe tablebases during the search
 
           else // If DTZ tables are missing, use WDL tables as a fallback
           {
               // Filter out moves that do not preserve a draw or win
-              TB::RootInTB = Tablebases::root_probe_wdl(RootPos, TB::Score);
+              TB::RootInTB = Tablebases::root_probe_wdl(RootPos, RootMoves, TB::Score);
 
               // Only probe during search if winning
               if (TB::Score <= VALUE_DRAW)

src/search.h

@@ -68,6 +68,7 @@ struct RootMove {
   std::vector<Move> pv;
 };
 
+typedef std::vector<RootMove> RootMoveVector;
 
 /// The LimitsType struct stores information sent by GUI about available time
 /// to search the current move, maximum depth/time, if we are in analysis mode
@@ -98,7 +99,7 @@ typedef std::auto_ptr<std::stack<StateInfo> > StateStackPtr;
 
 extern volatile SignalsType Signals;
 extern LimitsType Limits;
-extern std::vector<RootMove> RootMoves;
+extern RootMoveVector RootMoves;
 extern Position RootPos;
 extern Time::point SearchTime;
 extern StateStackPtr SetupStates;

src/syzygy/tbcore.cpp

@@ -223,8 +223,8 @@ static void init_tb(char *str)
     entry->num += pcs[i];
   entry->symmetric = (key == key2);
   entry->has_pawns = (pcs[TB_WPAWN] + pcs[TB_BPAWN] > 0);
-  if (entry->num > Tablebases::TBLargest)
-    Tablebases::TBLargest = entry->num;
+  if (entry->num > Tablebases::MaxCardinality)
+    Tablebases::MaxCardinality = entry->num;
 
   if (entry->has_pawns) {
     struct TBEntry_pawn *ptr = (struct TBEntry_pawn *)entry;
@@ -301,7 +301,7 @@ void Tablebases::init(const std::string& path)
   LOCK_INIT(TB_mutex);
 
   TBnum_piece = TBnum_pawn = 0;
-  TBLargest = 0;
+  MaxCardinality = 0;
 
   for (i = 0; i < (1 << TBHASHBITS); i++)
     for (j = 0; j < HSHMAX; j++) {

src/syzygy/tbprobe.cpp

@@ -22,7 +22,7 @@ namespace Zobrist {
   extern Key psq[COLOR_NB][PIECE_TYPE_NB][SQUARE_NB];
 }
 
-int Tablebases::TBLargest = 0;
+int Tablebases::MaxCardinality = 0;
 
 // Given a position with 6 or fewer pieces, produce a text string
 // of the form KQPvKRP, where "KQP" represents the white pieces if
@@ -32,7 +32,7 @@ static void prt_str(Position& pos, char *str, int mirror)
   Color color;
   PieceType pt;
   int i;
-  
+
   color = !mirror ? WHITE : BLACK;
   for (pt = KING; pt >= PAWN; --pt)
     for (i = popcount<Max15>(pos.pieces(color, pt)); i > 0; i--)
@@ -681,7 +681,7 @@ static Value wdl_to_Value[5] = {
 //
 // A return value false indicates that not all probes were successful and that
 // no moves were filtered out.
-bool Tablebases::root_probe(Position& pos, Value& TBScore)
+bool Tablebases::root_probe(Position& pos, Search::RootMoveVector& rootMoves, Value& score)
 {
   int success;
 
@@ -692,8 +692,8 @@ bool Tablebases::root_probe(Position& pos, Value& TBScore)
   CheckInfo ci(pos);
 
   // Probe each move.
-  for (size_t i = 0; i < Search::RootMoves.size(); i++) {
-    Move move = Search::RootMoves[i].pv[0];
+  for (size_t i = 0; i < rootMoves.size(); i++) {
+    Move move = rootMoves[i].pv[0];
     pos.do_move(move, st, ci, pos.gives_check(move, ci));
     int v = 0;
     if (pos.checkers() && dtz > 0) {
@@ -713,7 +713,7 @@ bool Tablebases::root_probe(Position& pos, Value& TBScore)
     }
     pos.undo_move(move);
     if (!success) return false;
-    Search::RootMoves[i].score = (Value)v;
+    rootMoves[i].score = (Value)v;
   }
 
   // Obtain 50-move counter for the root position.
@@ -729,21 +729,21 @@ bool Tablebases::root_probe(Position& pos, Value& TBScore)
     wdl = (-dtz + cnt50 <= 100) ? -2 : -1;
 
   // Determine the score to report to the user.
-  TBScore = wdl_to_Value[wdl + 2];
+  score = wdl_to_Value[wdl + 2];
   // If the position is winning or losing, but too few moves left, adjust the
   // score to show how close it is to winning or losing.
   // NOTE: int(PawnValueEg) is used as scaling factor in score_to_uci().
   if (wdl == 1 && dtz <= 100)
-    TBScore = (Value)(((200 - dtz - cnt50) * int(PawnValueEg)) / 200);
+    score = (Value)(((200 - dtz - cnt50) * int(PawnValueEg)) / 200);
   else if (wdl == -1 && dtz >= -100)
-    TBScore = -(Value)(((200 + dtz - cnt50) * int(PawnValueEg)) / 200);
+    score = -(Value)(((200 + dtz - cnt50) * int(PawnValueEg)) / 200);
 
   // Now be a bit smart about filtering out moves.
   size_t j = 0;
   if (dtz > 0) { // winning (or 50-move rule draw)
     int best = 0xffff;
-    for (size_t i = 0; i < Search::RootMoves.size(); i++) {
-      int v = Search::RootMoves[i].score;
+    for (size_t i = 0; i < rootMoves.size(); i++) {
+      int v = rootMoves[i].score;
       if (v > 0 && v < best)
         best = v;
     }
@@ -752,33 +752,33 @@ bool Tablebases::root_probe(Position& pos, Value& TBScore)
     // that stay safely within the 50-move budget, if there are any.
     if (!has_repeated(st.previous) && best + cnt50 <= 99)
       max = 99 - cnt50;
-    for (size_t i = 0; i < Search::RootMoves.size(); i++) {
-      int v = Search::RootMoves[i].score;
+    for (size_t i = 0; i < rootMoves.size(); i++) {
+      int v = rootMoves[i].score;
       if (v > 0 && v <= max)
-        Search::RootMoves[j++] = Search::RootMoves[i];
+        rootMoves[j++] = rootMoves[i];
     }
   } else if (dtz < 0) { // losing (or 50-move rule draw)
     int best = 0;
-    for (size_t i = 0; i < Search::RootMoves.size(); i++) {
-      int v = Search::RootMoves[i].score;
+    for (size_t i = 0; i < rootMoves.size(); i++) {
+      int v = rootMoves[i].score;
       if (v < best)
         best = v;
     }
     // Try all moves, unless we approach or have a 50-move rule draw.
     if (-best * 2 + cnt50 < 100)
       return true;
-    for (size_t i = 0; i < Search::RootMoves.size(); i++) {
-      if (Search::RootMoves[i].score == best)
-        Search::RootMoves[j++] = Search::RootMoves[i];
+    for (size_t i = 0; i < rootMoves.size(); i++) {
+      if (rootMoves[i].score == best)
+        rootMoves[j++] = rootMoves[i];
     }
   } else { // drawing
     // Try all moves that preserve the draw.
-    for (size_t i = 0; i < Search::RootMoves.size(); i++) {
-      if (Search::RootMoves[i].score == 0)
-        Search::RootMoves[j++] = Search::RootMoves[i];
+    for (size_t i = 0; i < rootMoves.size(); i++) {
+      if (rootMoves[i].score == 0)
+        rootMoves[j++] = rootMoves[i];
     }
   }
-  Search::RootMoves.resize(j, Search::RootMove(MOVE_NONE));
+  rootMoves.resize(j, Search::RootMove(MOVE_NONE));
 
   return true;
 }
@@ -788,37 +788,37 @@ bool Tablebases::root_probe(Position& pos, Value& TBScore)
 //
 // A return value false indicates that not all probes were successful and that
 // no moves were filtered out.
-bool Tablebases::root_probe_wdl(Position& pos, Value& TBScore)
+bool Tablebases::root_probe_wdl(Position& pos, Search::RootMoveVector& rootMoves, Value& score)
 {
   int success;
 
   int wdl = Tablebases::probe_wdl(pos, &success);
   if (!success) return false;
-  TBScore = wdl_to_Value[wdl + 2];
+  score = wdl_to_Value[wdl + 2];
 
   StateInfo st;
   CheckInfo ci(pos);
 
   int best = -2;
 
   // Probe each move.
-  for (size_t i = 0; i < Search::RootMoves.size(); i++) {
-    Move move = Search::RootMoves[i].pv[0];
+  for (size_t i = 0; i < rootMoves.size(); i++) {
+    Move move = rootMoves[i].pv[0];
     pos.do_move(move, st, ci, pos.gives_check(move, ci));
     int v = -Tablebases::probe_wdl(pos, &success);
     pos.undo_move(move);
     if (!success) return false;
-    Search::RootMoves[i].score = (Value)v;
+    rootMoves[i].score = (Value)v;
     if (v > best)
       best = v;
   }
 
   size_t j = 0;
-  for (size_t i = 0; i < Search::RootMoves.size(); i++) {
-    if (Search::RootMoves[i].score == best)
-      Search::RootMoves[j++] = Search::RootMoves[i];
+  for (size_t i = 0; i < rootMoves.size(); i++) {
+    if (rootMoves[i].score == best)
+      rootMoves[j++] = rootMoves[i];
   }
-  Search::RootMoves.resize(j, Search::RootMove(MOVE_NONE));
+  rootMoves.resize(j, Search::RootMove(MOVE_NONE));
 
   return true;
 }

src/syzygy/tbprobe.h

@@ -1,15 +1,17 @@
 #ifndef TBPROBE_H
 #define TBPROBE_H
 
+#include "../search.h"
+
 namespace Tablebases {
 
-extern int TBLargest;
+extern int MaxCardinality;
 
 void init(const std::string& path);
 int probe_wdl(Position& pos, int *success);
 int probe_dtz(Position& pos, int *success);
-bool root_probe(Position& pos, Value& TBScore);
-bool root_probe_wdl(Position& pos, Value& TBScore);
+bool root_probe(Position& pos, Search::RootMoveVector& rootMoves, Value& score);
+bool root_probe_wdl(Position& pos, Search::RootMoveVector& rootMoves, Value& score);
 
 }