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Further simplify first_entry()

Browse source 
We can encode the ClusterSize directly in the
hashMask, this allows to skip the left shift.

There is no real change, but bench number is now
different because instead of using the lowest order
bits of the key to index the start of the cluster,
now we don't use the last two lsb bits that are
always set to zero (cluster size is 4). So for
instance, if 10 bits are used to index the cluster,
instead of bits [9..0] now we use bits [11..2].
This changes the positions that end up in the same
cluster affecting TT hits and so bench is different.

Also some renaming while there.

bench: 5383795
This commit is contained in:
Marco Costalba 2013-02-09 16:22:47 +01:00
parent c698362680
commit 0be7b8c542
2 changed files with 11 additions and 11 deletions
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14
src/tt.cpp
View file

@ -34,16 +34,16 @@ void TranspositionTable::set_size(size_t mbSize) {
assert(msb((mbSize << 20) / sizeof(TTEntry)) < 32);
uint32_t size = 1 << msb((mbSize << 20) / sizeof(TTEntry[ClusterSize]));
uint32_t size = ClusterSize << msb((mbSize << 20) / sizeof(TTEntry[ClusterSize]));
if (clusterMask == size - 1)
if (hashMask == size - ClusterSize)
return;
clusterMask = size - 1;
delete [] entries;
entries = new (std::nothrow) TTEntry[size * ClusterSize];
hashMask = size - ClusterSize;
delete [] table;
table = new (std::nothrow) TTEntry[size];
if (!entries)
if (!table)
{
std::cerr << "Failed to allocate " << mbSize
<< "MB for transposition table." << std::endl;
@ -60,7 +60,7 @@ void TranspositionTable::set_size(size_t mbSize) {
void TranspositionTable::clear() {
memset(entries, 0, (clusterMask + 1) * sizeof(TTEntry[ClusterSize]));
memset(table, 0, (hashMask + ClusterSize) * sizeof(TTEntry));
}

8
src/tt.h
View file

@ -85,7 +85,7 @@ class TranspositionTable {
static const unsigned ClusterSize = 4; // A cluster is 64 Bytes
public:
~TranspositionTable() { delete [] entries; }
~TranspositionTable() { delete [] table; }
void new_search() { generation++; }
TTEntry* probe(const Key key) const;
@ -96,8 +96,8 @@ public:
void store(const Key key, Value v, Bound type, Depth d, Move m, Value statV, Value kingD);
private:
uint32_t clusterMask;
TTEntry* entries;
uint32_t hashMask;
TTEntry* table;
uint8_t generation; // Size must be not bigger then TTEntry::generation8
};
@ -110,7 +110,7 @@ extern TranspositionTable TT;
inline TTEntry* TranspositionTable::first_entry(const Key key) const {
return entries + ((uint32_t)key & clusterMask) * ClusterSize;
return table + ((uint32_t)key & hashMask);
}