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Rename FromTo -> History (#963)

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Previously, we had duplicated History:

- one with (piece,to) called History
- one with (from,to) called FromTo

Now that we have only one, rename it to History, which is the generally accepted
name in the chess programming litterature for this technique.

Also correct some comments that had not been updated since the introduction of CMH.

No functional change.
This commit is contained in:
lucasart
2017-01-10 15:47:56 +08:00
committed by Marco Costalba
parent e0504ab876
commit 34e47ca87d
4 changed files with 41 additions and 39 deletions
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60
src/movepick.h
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@@ -29,13 +29,37 @@
#include "types.h"
/// The Stats struct stores moves statistics. According to the template parameter
/// the class can store History and Countermoves. History records how often
/// different moves have been successful or unsuccessful during the current search
/// and is used for reduction and move ordering decisions.
/// Countermoves store the move that refute a previous one. Entries are stored
/// using only the moving piece and destination square, hence two moves with
/// different origin but same destination and piece will be considered identical.
/// HistoryStats records how often quiet moves have been successful or unsuccessful
/// during the current search, and is used for reduction and move ordering decisions.
struct HistoryStats {
static const Value Max = Value(1 << 28);
Value get(Color c, Move m) const { return table[c][from_sq(m)][to_sq(m)]; }
void clear() { std::memset(table, 0, sizeof(table)); }
void update(Color c, Move m, Value v) {
if (abs(int(v)) >= 324)
return;
Square from = from_sq(m);
Square to = to_sq(m);
table[c][from][to] -= table[c][from][to] * abs(int(v)) / 324;
table[c][from][to] += int(v) * 32;
}
private:
Value table[COLOR_NB][SQUARE_NB][SQUARE_NB];
};
/// A template struct, used to generate MoveStats and CounterMoveHistoryStats:
/// MoveStats store the move that refute a previous one.
/// CounterMoveHistoryStats is like HistoryStats, but with two consecutive moves.
/// Entries are stored using only the moving piece and destination square, hence
/// two moves with different origin but same destination and piece will be
/// considered identical.
template<typename T, bool CM = false>
struct Stats {
const T* operator[](Piece pc) const { return table[pc]; }
@@ -59,28 +83,6 @@ typedef Stats<Move> MoveStats;
typedef Stats<Value, true> CounterMoveStats;
typedef Stats<CounterMoveStats> CounterMoveHistoryStats;
struct FromToStats {
static const Value Max = Value(1 << 28);
Value get(Color c, Move m) const { return table[c][from_sq(m)][to_sq(m)]; }
void clear() { std::memset(table, 0, sizeof(table)); }
void update(Color c, Move m, Value v) {
if (abs(int(v)) >= 324)
return;
Square from = from_sq(m);
Square to = to_sq(m);
table[c][from][to] -= table[c][from][to] * abs(int(v)) / 324;
table[c][from][to] += int(v) * 32;
}
private:
Value table[COLOR_NB][SQUARE_NB][SQUARE_NB];
};
/// MovePicker class is used to pick one pseudo legal move at a time from the
/// current position. The most important method is next_move(), which returns a