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Code Issues Releases Wiki Activity

Revert saving of null search value in TT

Browse source 
Revert all the patches that introduced the change and
more or less fixed the zugzwang issue.

There is a gain against last current version and we
can remove a lot of code.

After 979 games at 1+0 on my QUAD
Mod vs Orig +152 =688 -139 +5 ELO

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2010-04-16 06:19:33 +01:00
parent ec0a650dff
commit 65c2715d9a
3 changed files with 39 additions and 59 deletions
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80
src/search.cpp
View file

@ -104,13 +104,6 @@ namespace {
}; };
// FIXME: document me
enum NullStatus {
ALLOW_NULLMOVE,
FORBID_NULLMOVE,
VERIFY_NULLMOVE
};
// RootMove struct is used for moves at the root at the tree. For each // RootMove struct is used for moves at the root at the tree. For each
// root move, we store a score, a node count, and a PV (really a refutation // root move, we store a score, a node count, and a PV (really a refutation
@ -288,7 +281,7 @@ namespace {
Value id_loop(const Position& pos, Move searchMoves[]); Value id_loop(const Position& pos, Move searchMoves[]);
Value root_search(Position& pos, SearchStack ss[], RootMoveList& rml, Value* alphaPtr, Value* betaPtr); Value root_search(Position& pos, SearchStack ss[], RootMoveList& rml, Value* alphaPtr, Value* betaPtr);
Value search_pv(Position& pos, SearchStack ss[], Value alpha, Value beta, Depth depth, int ply, int threadID); Value search_pv(Position& pos, SearchStack ss[], Value alpha, Value beta, Depth depth, int ply, int threadID);
Value search(Position& pos, SearchStack ss[], Value beta, Depth depth, int ply, NullStatus nullStatus, int threadID, Move excludedMove = MOVE_NONE); Value search(Position& pos, SearchStack ss[], Value beta, Depth depth, int ply, bool allowNullmove, int threadID, Move excludedMove = MOVE_NONE);
Value qsearch(Position& pos, SearchStack ss[], Value alpha, Value beta, Depth depth, int ply, int threadID); Value qsearch(Position& pos, SearchStack ss[], Value alpha, Value beta, Depth depth, int ply, int threadID);
void sp_search(SplitPoint* sp, int threadID); void sp_search(SplitPoint* sp, int threadID);
void sp_search_pv(SplitPoint* sp, int threadID); void sp_search_pv(SplitPoint* sp, int threadID);
@ -301,7 +294,7 @@ namespace {
Depth extension(const Position&, Move, bool, bool, bool, bool, bool, bool*); Depth extension(const Position&, Move, bool, bool, bool, bool, bool, bool*);
bool ok_to_do_nullmove(const Position& pos); bool ok_to_do_nullmove(const Position& pos);
bool ok_to_prune(const Position& pos, Move m, Move threat); 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, bool allowNullmove); bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply);
Value refine_eval(const TTEntry* tte, Value defaultEval, int ply); Value refine_eval(const TTEntry* tte, Value defaultEval, int ply);
void update_history(const Position& pos, Move move, Depth depth, Move movesSearched[], int moveCount); void update_history(const Position& pos, Move move, Depth depth, Move movesSearched[], int moveCount);
void update_killers(Move m, SearchStack& ss); void update_killers(Move m, SearchStack& ss);
@ -893,7 +886,7 @@ namespace {
if (ss[0].reduction) if (ss[0].reduction)
{ {
// Reduced depth non-pv search using alpha as upperbound // Reduced depth non-pv search using alpha as upperbound
value = -search(pos, ss, -alpha, newDepth-ss[0].reduction, 1, ALLOW_NULLMOVE, 0); value = -search(pos, ss, -alpha, newDepth-ss[0].reduction, 1, true, 0);
doFullDepthSearch = (value > alpha); doFullDepthSearch = (value > alpha);
} }
} }
@ -903,7 +896,7 @@ namespace {
{ {
// Full depth non-pv search using alpha as upperbound // Full depth non-pv search using alpha as upperbound
ss[0].reduction = Depth(0); ss[0].reduction = Depth(0);
value = -search(pos, ss, -alpha, newDepth, 1, ALLOW_NULLMOVE, 0); value = -search(pos, ss, -alpha, newDepth, 1, true, 0);
// If we are above alpha then research at same depth but as PV // If we are above alpha then research at same depth but as PV
// to get a correct score or eventually a fail high above beta. // to get a correct score or eventually a fail high above beta.
@ -1138,7 +1131,7 @@ namespace {
if (abs(ttValue) < VALUE_KNOWN_WIN) if (abs(ttValue) < VALUE_KNOWN_WIN)
{ {
Value excValue = search(pos, ss, ttValue - SingularExtensionMargin, depth / 2, ply, FORBID_NULLMOVE, threadID, move); Value excValue = search(pos, ss, ttValue - SingularExtensionMargin, depth / 2, ply, false, threadID, move);
if (excValue < ttValue - SingularExtensionMargin) if (excValue < ttValue - SingularExtensionMargin)
ext = OnePly; ext = OnePly;
@ -1174,7 +1167,7 @@ namespace {
ss[ply].reduction = pv_reduction(depth, moveCount); ss[ply].reduction = pv_reduction(depth, moveCount);
if (ss[ply].reduction) if (ss[ply].reduction)
{ {
value = -search(pos, ss, -alpha, newDepth-ss[ply].reduction, ply+1, ALLOW_NULLMOVE, threadID); value = -search(pos, ss, -alpha, newDepth-ss[ply].reduction, ply+1, true, threadID);
doFullDepthSearch = (value > alpha); doFullDepthSearch = (value > alpha);
} }
} }
@ -1183,7 +1176,7 @@ namespace {
if (doFullDepthSearch) if (doFullDepthSearch)
{ {
ss[ply].reduction = Depth(0); ss[ply].reduction = Depth(0);
value = -search(pos, ss, -alpha, newDepth, ply+1, ALLOW_NULLMOVE, threadID); value = -search(pos, ss, -alpha, newDepth, ply+1, true, threadID);
// Step extra. pv search (only in PV nodes) // Step extra. pv search (only in PV nodes)
if (value > alpha && value < beta) if (value > alpha && value < beta)
@ -1258,7 +1251,7 @@ namespace {
// search() is the search function for zero-width nodes. // search() is the search function for zero-width nodes.
Value search(Position& pos, SearchStack ss[], Value beta, Depth depth, Value search(Position& pos, SearchStack ss[], Value beta, Depth depth,
int ply, NullStatus nullStatus, int threadID, Move excludedMove) { int ply, bool allowNullmove, int threadID, Move excludedMove) {
assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE); assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
assert(ply >= 0 && ply < PLY_MAX); assert(ply >= 0 && ply < PLY_MAX);
@ -1306,7 +1299,7 @@ namespace {
tte = TT.retrieve(posKey); tte = TT.retrieve(posKey);
ttMove = (tte ? tte->move() : MOVE_NONE); ttMove = (tte ? tte->move() : MOVE_NONE);
if (tte && ok_to_use_TT(tte, depth, beta, ply, nullStatus != VERIFY_NULLMOVE)) if (tte && ok_to_use_TT(tte, depth, beta, ply))
{ {
ss[ply].currentMove = ttMove; // Can be MOVE_NONE ss[ply].currentMove = ttMove; // Can be MOVE_NONE
return value_from_tt(tte->value(), ply); return value_from_tt(tte->value(), ply);
@ -1346,7 +1339,7 @@ namespace {
// Step 7. Static null move pruning // Step 7. Static null move pruning
// We're betting that the opponent doesn't have a move that will reduce // We're betting that the opponent doesn't have a move that will reduce
// the score by more than futility_margin(depth) if we do a null move. // the score by more than futility_margin(depth) if we do a null move.
if ( nullStatus == ALLOW_NULLMOVE if ( allowNullmove
&& depth < RazorDepth && depth < RazorDepth
&& !isCheck && !isCheck
&& !value_is_mate(beta) && !value_is_mate(beta)
@ -1358,7 +1351,7 @@ namespace {
// When we jump directly to qsearch() we do a null move only if static value is // When we jump directly to qsearch() we do a null move only if static value is
// at least beta. Otherwise we do a null move if static value is not more than // at least beta. Otherwise we do a null move if static value is not more than
// NullMoveMargin under beta. // NullMoveMargin under beta.
if ( nullStatus == ALLOW_NULLMOVE if ( allowNullmove
&& depth > OnePly && depth > OnePly
&& !isCheck && !isCheck
&& !value_is_mate(beta) && !value_is_mate(beta)
@ -1376,7 +1369,7 @@ namespace {
pos.do_null_move(st); pos.do_null_move(st);
nullValue = -search(pos, ss, -(beta-1), depth-R*OnePly, ply+1, FORBID_NULLMOVE, threadID); nullValue = -search(pos, ss, -(beta-1), depth-R*OnePly, ply+1, false, threadID);
pos.undo_null_move(); pos.undo_null_move();
@ -1386,20 +1379,13 @@ namespace {
if (nullValue >= value_mate_in(PLY_MAX)) if (nullValue >= value_mate_in(PLY_MAX))
nullValue = beta; nullValue = beta;
// Do zugzwang verification search for high depths, don't store in TT if (depth < 6 * OnePly)
// if search was stopped. return nullValue;
if ( ( depth < 6 * OnePly
|| search(pos, ss, beta, depth-5*OnePly, ply, VERIFY_NULLMOVE, threadID) >= beta) // Do zugzwang verification search
&& !AbortSearch Value v = search(pos, ss, beta, depth-5*OnePly, ply, false, threadID);
&& !TM.thread_should_stop(threadID)) if (v >= beta)
{
assert(value_to_tt(nullValue, ply) == nullValue);
if (!tte)
TT.store(posKey, nullValue, VALUE_TYPE_NS_LO, depth, MOVE_NONE);
return nullValue; return nullValue;
}
} else { } else {
// The null move failed low, which means that we may be faced with // The null move failed low, which means that we may be faced with
// some kind of threat. If the previous move was reduced, check if // some kind of threat. If the previous move was reduced, check if
@ -1424,7 +1410,7 @@ namespace {
&& !isCheck && !isCheck
&& ss[ply].eval >= beta - IIDMargin) && ss[ply].eval >= beta - IIDMargin)
{ {
search(pos, ss, beta, depth/2, ply, FORBID_NULLMOVE, threadID); search(pos, ss, beta, depth/2, ply, false, threadID);
ttMove = ss[ply].pv[ply]; ttMove = ss[ply].pv[ply];
tte = TT.retrieve(posKey); tte = TT.retrieve(posKey);
} }
@ -1466,7 +1452,7 @@ namespace {
if (abs(ttValue) < VALUE_KNOWN_WIN) if (abs(ttValue) < VALUE_KNOWN_WIN)
{ {
Value excValue = search(pos, ss, ttValue - SingularExtensionMargin, depth / 2, ply, FORBID_NULLMOVE, threadID, move); Value excValue = search(pos, ss, ttValue - SingularExtensionMargin, depth / 2, ply, false, threadID, move);
if (excValue < ttValue - SingularExtensionMargin) if (excValue < ttValue - SingularExtensionMargin)
ext = OnePly; ext = OnePly;
@ -1520,7 +1506,7 @@ namespace {
ss[ply].reduction = nonpv_reduction(depth, moveCount); ss[ply].reduction = nonpv_reduction(depth, moveCount);
if (ss[ply].reduction) if (ss[ply].reduction)
{ {
value = -search(pos, ss, -(beta-1), newDepth-ss[ply].reduction, ply+1, ALLOW_NULLMOVE, threadID); value = -search(pos, ss, -(beta-1), newDepth-ss[ply].reduction, ply+1, true, threadID);
doFullDepthSearch = (value >= beta); doFullDepthSearch = (value >= beta);
} }
} }
@ -1529,7 +1515,7 @@ namespace {
if (doFullDepthSearch) if (doFullDepthSearch)
{ {
ss[ply].reduction = Depth(0); ss[ply].reduction = Depth(0);
value = -search(pos, ss, -(beta-1), newDepth, ply+1, ALLOW_NULLMOVE, threadID); value = -search(pos, ss, -(beta-1), newDepth, ply+1, true, threadID);
} }
// Step 16. Undo move // Step 16. Undo move
@ -1634,7 +1620,7 @@ namespace {
tte = TT.retrieve(pos.get_key()); tte = TT.retrieve(pos.get_key());
ttMove = (tte ? tte->move() : MOVE_NONE); ttMove = (tte ? tte->move() : MOVE_NONE);
if (!pvNode && tte && ok_to_use_TT(tte, depth, beta, ply, true)) if (!pvNode && tte && ok_to_use_TT(tte, depth, beta, ply))
{ {
assert(tte->type() != VALUE_TYPE_EVAL); assert(tte->type() != VALUE_TYPE_EVAL);
@ -1879,7 +1865,7 @@ namespace {
ss[sp->ply].reduction = nonpv_reduction(sp->depth, moveCount); ss[sp->ply].reduction = nonpv_reduction(sp->depth, moveCount);
if (ss[sp->ply].reduction) if (ss[sp->ply].reduction)
{ {
value = -search(pos, ss, -(sp->beta-1), newDepth-ss[sp->ply].reduction, sp->ply+1, ALLOW_NULLMOVE, threadID); value = -search(pos, ss, -(sp->beta-1), newDepth-ss[sp->ply].reduction, sp->ply+1, true, threadID);
doFullDepthSearch = (value >= sp->beta && !TM.thread_should_stop(threadID)); doFullDepthSearch = (value >= sp->beta && !TM.thread_should_stop(threadID));
} }
} }
@ -1888,7 +1874,7 @@ namespace {
if (doFullDepthSearch) if (doFullDepthSearch)
{ {
ss[sp->ply].reduction = Depth(0); ss[sp->ply].reduction = Depth(0);
value = -search(pos, ss, -(sp->beta - 1), newDepth, sp->ply+1, ALLOW_NULLMOVE, threadID); value = -search(pos, ss, -(sp->beta - 1), newDepth, sp->ply+1, true, threadID);
} }
// Step 16. Undo move // Step 16. Undo move
@ -1985,7 +1971,7 @@ namespace {
if (ss[sp->ply].reduction) if (ss[sp->ply].reduction)
{ {
Value localAlpha = sp->alpha; Value localAlpha = sp->alpha;
value = -search(pos, ss, -localAlpha, newDepth-ss[sp->ply].reduction, sp->ply+1, ALLOW_NULLMOVE, threadID); value = -search(pos, ss, -localAlpha, newDepth-ss[sp->ply].reduction, sp->ply+1, true, threadID);
doFullDepthSearch = (value > localAlpha && !TM.thread_should_stop(threadID)); doFullDepthSearch = (value > localAlpha && !TM.thread_should_stop(threadID));
} }
} }
@ -1995,7 +1981,7 @@ namespace {
{ {
Value localAlpha = sp->alpha; Value localAlpha = sp->alpha;
ss[sp->ply].reduction = Depth(0); ss[sp->ply].reduction = Depth(0);
value = -search(pos, ss, -localAlpha, newDepth, sp->ply+1, ALLOW_NULLMOVE, threadID); value = -search(pos, ss, -localAlpha, newDepth, sp->ply+1, true, threadID);
if (value > localAlpha && value < sp->beta && !TM.thread_should_stop(threadID)) if (value > localAlpha && value < sp->beta && !TM.thread_should_stop(threadID))
{ {
@ -2315,18 +2301,14 @@ namespace {
} }
// ok_to_use_TT() returns true if a transposition table score can be used at a // ok_to_use_TT() returns true if a transposition table score
// given point in search. To avoid zugzwang issues TT cutoffs at the root node // can be used at a given point in search.
// of a null move verification search are not allowed if the TT value was found
// by a null search, this is implemented testing allowNullmove and TT entry type.
bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply, bool allowNullmove) { bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply) {
Value v = value_from_tt(tte->value(), ply); Value v = value_from_tt(tte->value(), ply);
return (allowNullmove || !(tte->type() & VALUE_TYPE_NULL)) return ( tte->depth() >= depth
&& ( tte->depth() >= depth
|| v >= Max(value_mate_in(PLY_MAX), beta) || v >= Max(value_mate_in(PLY_MAX), beta)
|| v < Min(value_mated_in(PLY_MAX), beta)) || v < Min(value_mated_in(PLY_MAX), beta))

8
src/tt.h
View file

@ -46,8 +46,8 @@
/// the 32 bits of the data field are so defined /// the 32 bits of the data field are so defined
/// ///
/// bit 0-16: move /// bit 0-16: move
/// bit 17-18: not used /// bit 17-19: not used
/// bit 19-22: value type /// bit 20-22: value type
/// bit 23-31: generation /// bit 23-31: generation
class TTEntry { class TTEntry {
@ -55,14 +55,14 @@ class TTEntry {
public: public:
TTEntry() {} TTEntry() {}
TTEntry(uint32_t 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 << 19) | (generation << 23)), : key_ (k), data((m & 0x1FFFF) | (t << 20) | (generation << 23)),
value_(int16_t(v)), depth_(int16_t(d)) {} value_(int16_t(v)), depth_(int16_t(d)) {}
uint32_t key() const { return key_; } uint32_t key() const { return key_; }
Depth depth() const { return Depth(depth_); } Depth depth() const { return Depth(depth_); }
Move move() const { return Move(data & 0x1FFFF); } Move move() const { return Move(data & 0x1FFFF); }
Value value() const { return Value(value_); } Value value() const { return Value(value_); }
ValueType type() const { return ValueType((data >> 19) & 0xF); } ValueType type() const { return ValueType((data >> 20) & 7); }
int generation() const { return (data >> 23); } int generation() const { return (data >> 23); }
private: private:

6
src/value.h
View file

@ -36,13 +36,11 @@ enum ValueType {
VALUE_TYPE_NONE = 0, VALUE_TYPE_NONE = 0,
VALUE_TYPE_UPPER = 1, // Upper bound VALUE_TYPE_UPPER = 1, // Upper bound
VALUE_TYPE_LOWER = 2, // Lower bound VALUE_TYPE_LOWER = 2, // Lower bound
VALUE_TYPE_EXACT = 3, // Exact score
VALUE_TYPE_EVAL = 4, // Static evaluation value VALUE_TYPE_EVAL = 4, // Static evaluation value
VALUE_TYPE_NULL = 8, // Null search value
VALUE_TYPE_EXACT = VALUE_TYPE_UPPER | VALUE_TYPE_LOWER,
VALUE_TYPE_EV_UP = VALUE_TYPE_EVAL | VALUE_TYPE_UPPER, VALUE_TYPE_EV_UP = VALUE_TYPE_EVAL | VALUE_TYPE_UPPER,
VALUE_TYPE_EV_LO = VALUE_TYPE_EVAL | VALUE_TYPE_LOWER, VALUE_TYPE_EV_LO = VALUE_TYPE_EVAL | VALUE_TYPE_LOWER
VALUE_TYPE_NS_LO = VALUE_TYPE_NULL | VALUE_TYPE_LOWER
}; };