X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Ftt.cpp;h=375c00a67308fbc934e7cad2fe569f5a780468f3;hp=5c5e10c16b720115ca4b20fabb9c97dbd21ffd99;hb=9ca4359f3691305fc5e3306c3084c83557ce09c0;hpb=00e86078a550631e3d045d882ab27f827d3f2378

diff --git a/src/tt.cpp b/src/tt.cpp
index 5c5e10c1..375c00a6 100644
--- a/src/tt.cpp
+++ b/src/tt.cpp
@@ -25,7 +25,6 @@
 #include <cassert>
 #include <cstring>
 
-#include "movegen.h"
 #include "tt.h"
 
 // The main transposition table
@@ -55,8 +54,10 @@ void TranspositionTable::set_size(size_t mbSize) {
 
   size_t newSize = 1024;
 
-  // We store a cluster of ClusterSize number of TTEntry for each position
-  // and newSize is the maximum number of storable positions.
+  // Transposition table consists of clusters and
+  // each cluster consists of ClusterSize number of TTEntries.
+  // Each non-empty entry contains information of exactly one position.
+  // newSize is the number of clusters we are going to allocate.
   while ((2 * newSize) * sizeof(TTCluster) <= (mbSize << 20))
       newSize *= 2;
 
@@ -71,6 +72,7 @@ void TranspositionTable::set_size(size_t mbSize) {
                     << " MB for transposition table." << std::endl;
           Application::exit_with_failure();
       }
+      clear();
   }
 }
 
@@ -78,7 +80,7 @@ void TranspositionTable::set_size(size_t mbSize) {
 /// TranspositionTable::clear overwrites the entire transposition table
 /// with zeroes. It is called whenever the table is resized, or when the
 /// user asks the program to clear the table (from the UCI interface).
-/// Perhaps we should also clear it when the "ucinewgame" command is recieved?
+/// Perhaps we should also clear it when the "ucinewgame" command is received?
 
 void TranspositionTable::clear() {
 
@@ -86,15 +88,15 @@ void TranspositionTable::clear() {
 }
 
 
-/// TranspositionTable::store writes a new entry containing a position,
-/// a value, a value type, a search depth, and a best move to the
-/// transposition table. Transposition table is organized in clusters of
-/// four TTEntry objects, and when a new entry is written, it replaces
-/// the least valuable of the four entries in a cluster. A TTEntry t1 is
-/// considered to be more valuable than a TTEntry t2 if t1 is from the
+/// TranspositionTable::store writes a new entry containing position key and
+/// valuable information of current position.
+/// The Lowest order bits of position key are used to decide on which cluster
+/// the position will be placed.
+/// When a new entry is written and there are no empty entries available in cluster,
+/// it replaces the least valuable of entries.
+/// A TTEntry t1 is considered to be more valuable than a TTEntry t2 if t1 is from the
 /// current search and t2 is from a previous search, or if the depth of t1
-/// is bigger than the depth of t2. A TTEntry of type VALUE_TYPE_EVAL
-/// never replaces another entry for the same position.
+/// is bigger than the depth of t2.
 
 void TranspositionTable::store(const Key posKey, Value v, ValueType t, Depth d, Move m, Value statV, Value kingD) {
 
@@ -107,7 +109,7 @@ void TranspositionTable::store(const Key posKey, Value v, ValueType t, Depth d,
   {
       if (!tte->key() || tte->key() == posKey32) // empty or overwrite old
       {
-          // Preserve any exsisting ttMove
+          // Preserve any existing ttMove
           if (m == MOVE_NONE)
               m = tte->move();
 
@@ -115,7 +117,7 @@ void TranspositionTable::store(const Key posKey, Value v, ValueType t, Depth d,
           return;
       }
 
-      if (i == 0)  // replace would be a no-op in this common case
+      if (i == 0)  // Replacing first entry is default and already set before entering for-loop
           continue;
 
       c1 = (replace->generation() == generation ?  2 : 0);
@@ -154,57 +156,3 @@ TTEntry* TranspositionTable::retrieve(const Key posKey) const {
 void TranspositionTable::new_search() {
   generation++;
 }
-
-
-/// TranspositionTable::insert_pv() is called at the end of a search
-/// iteration, and inserts the PV back into the PV. This makes sure
-/// the old PV moves are searched first, even if the old TT entries
-/// have been overwritten.
-
-void TranspositionTable::insert_pv(const Position& pos, Move pv[]) {
-
-  StateInfo st;
-  Position p(pos, pos.thread());
-
-  for (int i = 0; pv[i] != MOVE_NONE; i++)
-  {
-      TTEntry *tte = retrieve(p.get_key());
-      if (!tte || tte->move() != pv[i])
-          store(p.get_key(), VALUE_NONE, VALUE_TYPE_NONE, Depth(-127*OnePly), pv[i], VALUE_NONE, VALUE_NONE);
-      p.do_move(pv[i], st);
-  }
-}
-
-
-/// TranspositionTable::extract_pv() extends a PV by adding moves from the
-/// transposition table at the end. This should ensure that the PV is almost
-/// always at least two plies long, which is important, because otherwise we
-/// will often get single-move PVs when the search stops while failing high,
-/// and a single-move PV means that we don't have a ponder move.
-
-void TranspositionTable::extract_pv(const Position& pos, Move bestMove, Move pv[], const int PLY_MAX) {
-
-  const TTEntry* tte;
-  StateInfo st;
-  Position p(pos, pos.thread());
-  int ply = 0;
-
-  assert(bestMove != MOVE_NONE);
-
-  pv[ply] = bestMove;
-  p.do_move(pv[ply++], st);
-
-  // Extract moves from TT when possible. We try hard to always
-  // get a ponder move, that's the reason of ply < 2 conditions.
-  while (   (tte = retrieve(p.get_key())) != NULL
-         && tte->move() != MOVE_NONE
-         && (tte->type() == VALUE_TYPE_EXACT || ply < 2)
-         && move_is_legal(p, tte->move())
-         && (!p.is_draw() || ply < 2)
-         && ply < PLY_MAX)
-  {
-      pv[ply] = tte->move();
-      p.do_move(pv[ply++], st);
-  }
-  pv[ply] = MOVE_NONE;
-}