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Use 32 bit key in TT

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Shrink key to 32 bits instead of 64. To still avoid
collisions use the high 32 bits of position key as the
TT key and the low 32 bits to retrieve the correct
cluster index in the table.

With this patch size og TTentry shrinks to 96 bits instead
of 128 and the cluster of 4 TTEntry sums to 48 bytes instead
of 64.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba
2009-08-09 04:19:32 +01:00
parent 4a777954e1
commit 6f1475b6fc
2 changed files with 29 additions and 22 deletions
Download Patch File Download Diff File Expand all files Collapse all files

16
src/tt.h
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@@ -36,12 +36,12 @@
/// The TTEntry class is the class of transposition table entries
///
/// A TTEntry needs 128 bits to be stored
/// A TTEntry needs 96 bits to be stored
///
/// bit 0-63: key
/// bit 64-95: data
/// bit 96-111: value
/// bit 112-127: depth
/// bit 0-31: key
/// bit 32-63: data
/// bit 64-79: value
/// bit 80-95: depth
///
/// the 32 bits of the data field are so defined
///
@@ -54,11 +54,11 @@ class TTEntry {
public:
TTEntry() {}
TTEntry(Key k, Value v, ValueType t, Depth d, Move m, int generation)
TTEntry(uint32_t k, Value v, ValueType t, Depth d, Move m, int generation)
: key_ (k), data((m & 0x1FFFF) | (t << 20) | (generation << 23)),
value_(int16_t(v)), depth_(int16_t(d)) {}
Key key() const { return key_; }
uint32_t key() const { return key_; }
Depth depth() const { return Depth(depth_); }
Move move() const { return Move(data & 0x1FFFF); }
Value value() const { return Value(value_); }
@@ -66,7 +66,7 @@ public:
int generation() const { return (data >> 23); }
private:
Key key_;
uint32_t key_;
uint32_t data;
int16_t value_;
int16_t depth_;