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Reduction lookup table

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No functional change

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Joona Kiiski 2010-02-04 18:09:07 +02:00 • committed by Marco Costalba
parent 439aea9ab7
commit 5b1043ee11
1 changed files with 25 additions and 65 deletions
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90
src/search.cpp
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@ -218,9 +218,13 @@ namespace {
bool UseLogFile;
std::ofstream LogFile;
// Natural logarithmic lookup table and its getter function
float lnArray[512];
inline float ln(int i) { return lnArray[i]; }
// Reduction lookup tables and their getter functions
// Initialized at startup
int8_t PVReductionMatrix[64][64]; // [depth][moveNumber]
int8_t NonPVReductionMatrix[64][64]; // [depth][moveNumber]
inline Depth pv_reduction(Depth d, int mn) { return (Depth) PVReductionMatrix[Min(d / 2, 63)][Min(mn, 63)]; }
inline Depth nonpv_reduction(Depth d, int mn) { return (Depth) NonPVReductionMatrix[Min(d / 2, 63)][Min(mn, 63)]; }
// MP related variables
int ActiveThreads = 1;
@ -268,8 +272,6 @@ namespace {
bool ok_to_prune(const Position& pos, Move m, Move threat);
bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply);
Value refine_eval(const TTEntry* tte, Value defaultEval, int ply);
void reduction_parameters(float base, float Inhibitor, Depth depth, float& logLimit, float& gradient);
Depth reduction(int moveCount, const float LogLimit, const float BaseRed, const float Gradient);
void update_history(const Position& pos, Move move, Depth depth, Move movesSearched[], int moveCount);
void update_killers(Move m, SearchStack& ss);
void update_gains(const Position& pos, Move move, Value before, Value after);
@ -551,12 +553,15 @@ void init_threads() {
pthread_t pthread[1];
#endif
// Init our logarithmic lookup table
for (i = 0; i < 512; i++)
lnArray[i] = float(log(double(i))); // log() returns base-e logarithm
for (i = 0; i < THREAD_MAX; i++)
Threads[i].activeSplitPoints = 0;
// Init our reduction lookup tables
for (i = 1; i < 64; i++) // i == depth
for (int j = 1; j < 64; j++) // j == moveNumber
{
double pvRed = 0.5 + log(double(i)) * log(double(j)) / 6.0;
double nonPVRed = 0.5 + log(double(i)) * log(double(j)) / 3.0;
PVReductionMatrix[i][j] = (int8_t) ( pvRed >= 1.0 ? floor( pvRed * int(OnePly)) : 0);
NonPVReductionMatrix[i][j] = (int8_t) (nonPVRed >= 1.0 ? floor(nonPVRed * int(OnePly)) : 0);
}
// Init futility margins array
FutilityMargins[0] = FutilityMargins[1] = Value(0);
@ -566,6 +571,9 @@ void init_threads() {
FutilityMargins[i] = Value(112 * bitScanReverse32(i * i / 2)); // FIXME: test using log instead of BSR
}
for (i = 0; i < THREAD_MAX; i++)
Threads[i].activeSplitPoints = 0;
// Initialize global locks
lock_init(&MPLock, NULL);
lock_init(&IOLock, NULL);
@ -913,10 +921,6 @@ namespace {
value = - VALUE_INFINITE;
// Precalculate reduction parameters
float LogLimit, Gradient, BaseReduction = 0.5;
reduction_parameters(BaseReduction, 6.0, depth, LogLimit, Gradient);
while (1) // Fail high loop
{
@ -952,7 +956,7 @@ namespace {
&& !captureOrPromotion
&& !move_is_castle(move))
{
ss[0].reduction = reduction(RootMoveNumber - MultiPV + 1, LogLimit, BaseReduction, Gradient);
ss[0].reduction = pv_reduction(depth, RootMoveNumber - MultiPV + 1);
if (ss[0].reduction)
{
value = -search(pos, ss, -alpha, newDepth-ss[0].reduction, 1, true, 0);
@ -1209,10 +1213,6 @@ namespace {
CheckInfo ci(pos);
MovePicker mp = MovePicker(pos, ttMove, depth, H, &ss[ply]);
// Precalculate reduction parameters
float LogLimit, Gradient, BaseReduction = 0.5;
reduction_parameters(BaseReduction, 6.0, depth, LogLimit, Gradient);
// Loop through all legal moves until no moves remain or a beta cutoff
// occurs.
while ( alpha < beta
@ -1271,7 +1271,7 @@ namespace {
&& !move_is_castle(move)
&& !move_is_killer(move, ss[ply]))
{
ss[ply].reduction = reduction(moveCount, LogLimit, BaseReduction, Gradient);
ss[ply].reduction = pv_reduction(depth, moveCount);
if (ss[ply].reduction)
{
value = -search(pos, ss, -alpha, newDepth-ss[ply].reduction, ply+1, true, threadID);
@ -1532,10 +1532,6 @@ namespace {
MovePicker mp = MovePicker(pos, ttMove, depth, H, &ss[ply]);
CheckInfo ci(pos);
// Precalculate reduction parameters
float LogLimit, Gradient, BaseReduction = 0.5;
reduction_parameters(BaseReduction, 3.0, depth, LogLimit, Gradient);
// Loop through all legal moves until no moves remain or a beta cutoff occurs
while ( bestValue < beta
&& (move = mp.get_next_move()) != MOVE_NONE
@ -1597,7 +1593,7 @@ namespace {
Depth predictedDepth = newDepth;
//FIXME: We are ignoring condition: depth >= 3*OnePly, BUG??
ss[ply].reduction = reduction(moveCount, LogLimit, BaseReduction, Gradient);
ss[ply].reduction = nonpv_reduction(depth, moveCount);
if (ss[ply].reduction)
predictedDepth -= ss[ply].reduction;
@ -1633,7 +1629,7 @@ namespace {
&& !move_is_castle(move)
&& !move_is_killer(move, ss[ply]))
{
ss[ply].reduction = reduction(moveCount, LogLimit, BaseReduction, Gradient);
ss[ply].reduction = nonpv_reduction(depth, moveCount);
if (ss[ply].reduction)
{
value = -search(pos, ss, -(beta-1), newDepth-ss[ply].reduction, ply+1, true, threadID);
@ -1920,10 +1916,6 @@ namespace {
const int FutilityMoveCountMargin = 3 + (1 << (3 * int(sp->depth) / 8));
// Precalculate reduction parameters
float LogLimit, Gradient, BaseReduction = 0.5;
reduction_parameters(BaseReduction, 3.0, sp->depth, LogLimit, Gradient);
while ( lock_grab_bool(&(sp->lock))
&& sp->bestValue < sp->beta
&& !thread_should_stop(threadID)
@ -1984,7 +1976,7 @@ namespace {
&& !move_is_castle(move)
&& !move_is_killer(move, ss[sp->ply]))
{
ss[sp->ply].reduction = reduction(moveCount, LogLimit, BaseReduction, Gradient);
ss[sp->ply].reduction = nonpv_reduction(sp->depth, moveCount);
if (ss[sp->ply].reduction)
{
value = -search(pos, ss, -(sp->beta-1), newDepth-ss[sp->ply].reduction, sp->ply+1, true, threadID);
@ -2064,10 +2056,6 @@ namespace {
int moveCount;
Move move;
// Precalculate reduction parameters
float LogLimit, Gradient, BaseReduction = 0.5;
reduction_parameters(BaseReduction, 6.0, sp->depth, LogLimit, Gradient);
while ( lock_grab_bool(&(sp->lock))
&& sp->alpha < sp->beta
&& !thread_should_stop(threadID)
@ -2101,7 +2089,7 @@ namespace {
&& !move_is_castle(move)
&& !move_is_killer(move, ss[sp->ply]))
{
ss[sp->ply].reduction = reduction(moveCount, LogLimit, BaseReduction, Gradient);
ss[sp->ply].reduction = pv_reduction(sp->depth, moveCount);
if (ss[sp->ply].reduction)
{
Value localAlpha = sp->alpha;
@ -2628,34 +2616,6 @@ namespace {
}
// reduction_parameters() precalculates some parameters used later by reduction. Becasue
// floating point operations are involved we try to recalculate reduction at each move, but
// we do the most consuming computation only once per node.
void reduction_parameters(float baseReduction, float reductionInhibitor, Depth depth, float& logLimit, float& gradient)
{
// Precalculate some parameters to avoid to calculate the following formula for each move:
//
// red = baseReduction + ln(moveCount) * ln(depth / 2) / reductionInhibitor;
//
logLimit = depth > OnePly ? (1 - baseReduction) * reductionInhibitor / ln(depth / 2) : 1000;
gradient = depth > OnePly ? ln(depth / 2) / reductionInhibitor : 0;
}
// reduction() returns reduction in plies based on moveCount and depth.
// Reduction is always at least one ply.
Depth reduction(int moveCount, float logLimit, float baseReduction, float gradient) {
if (ln(moveCount) < logLimit)
return Depth(0);
float red = baseReduction + ln(moveCount) * gradient;
return Depth(int(floor(red * int(OnePly))));
}
// update_history() registers a good move that produced a beta-cutoff
// in history and marks as failures all the other moves of that ply.