X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=30f280728e274055d49771ceb2a413d5b91aa9dd;hp=651bd95b6feff4ceecc70840ef82fb37bafbb86d;hb=1982fe25f817c29aef9dd156869a53e520ce3629;hpb=9050eac59564fe96b3f24d2889bbef7336b28100
diff --git a/src/search.cpp b/src/search.cpp
index 651bd95b..30f28072 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -18,7 +18,6 @@
along with this program. If not, see .
*/
-#include
#include
#include
#include // For std::memset
@@ -61,22 +60,22 @@ namespace {
// Different node types, used as a template parameter
enum NodeType { NonPV, PV };
- // Sizes and phases of the skip-blocks, used for distributing search depths across the threads
- constexpr int SkipSize[] = { 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4 };
- constexpr int SkipPhase[] = { 0, 1, 0, 1, 2, 3, 0, 1, 2, 3, 4, 5, 0, 1, 2, 3, 4, 5, 6, 7 };
-
// Razor and futility margins
constexpr int RazorMargin = 600;
Value futility_margin(Depth d, bool improving) {
return Value((175 - 50 * improving) * d / ONE_PLY);
}
- // Futility and reductions lookup tables, initialized at startup
- int FutilityMoveCounts[2][16]; // [improving][depth]
- int Reductions[2][2][64][64]; // [pv][improving][depth][moveNumber]
+ // Reductions lookup table, initialized at startup
+ int Reductions[64]; // [depth or moveNumber]
template Depth reduction(bool i, Depth d, int mn) {
- return Reductions[PvNode][i][std::min(d / ONE_PLY, 63)][std::min(mn, 63)] * ONE_PLY;
+ int r = Reductions[std::min(d / ONE_PLY, 63)] * Reductions[std::min(mn, 63)] / 1024;
+ return ((r + 512) / 1024 + (!i && r > 1024) - PvNode) * ONE_PLY;
+ }
+
+ constexpr int futility_move_count(bool improving, int depth) {
+ return (5 + depth * depth) * (1 + improving) / 2;
}
// History and stats update bonus, based on depth
@@ -85,11 +84,10 @@ namespace {
return d > 17 ? 0 : 29 * d * d + 138 * d - 134;
}
- // Add a small random component to draw evaluations to keep search dynamic
- // and to avoid 3fold-blindness.
+ // Add a small random component to draw evaluations to avoid 3fold-blindness
Value value_draw(Depth depth, Thread* thisThread) {
return depth < 4 ? VALUE_DRAW
- : VALUE_DRAW + Value(2 * (thisThread->nodes.load(std::memory_order_relaxed) % 2) - 1);
+ : VALUE_DRAW + Value(2 * (thisThread->nodes & 1) - 1);
}
// Skill structure is used to implement strength limit
@@ -116,13 +114,6 @@ namespace {
void update_quiet_stats(const Position& pos, Stack* ss, Move move, Move* quiets, int quietCount, int bonus);
void update_capture_stats(const Position& pos, Move move, Move* captures, int captureCount, int bonus);
- inline bool gives_check(const Position& pos, Move move) {
- Color us = pos.side_to_move();
- return type_of(move) == NORMAL && !(pos.blockers_for_king(~us) & pos.pieces(us))
- ? pos.check_squares(type_of(pos.moved_piece(move))) & to_sq(move)
- : pos.gives_check(move);
- }
-
// perft() is our utility to verify move generation. All the leaf nodes up
// to the given depth are generated and counted, and the sum is returned.
template
@@ -156,25 +147,8 @@ namespace {
void Search::init() {
- for (int imp = 0; imp <= 1; ++imp)
- for (int d = 1; d < 64; ++d)
- for (int mc = 1; mc < 64; ++mc)
- {
- double r = log(d) * log(mc) / 1.95;
-
- Reductions[NonPV][imp][d][mc] = int(std::round(r));
- Reductions[PV][imp][d][mc] = std::max(Reductions[NonPV][imp][d][mc] - 1, 0);
-
- // Increase reduction for non-PV nodes when eval is not improving
- if (!imp && r > 1.0)
- Reductions[NonPV][imp][d][mc]++;
- }
-
- for (int d = 0; d < 16; ++d)
- {
- FutilityMoveCounts[0][d] = int(2.4 + 0.74 * pow(d, 1.78));
- FutilityMoveCounts[1][d] = int(5.0 + 1.00 * pow(d, 2.00));
- }
+ for (int i = 1; i < 64; ++i)
+ Reductions[i] = int(1024 * std::log(i) / std::sqrt(1.95));
}
@@ -187,12 +161,12 @@ void Search::clear() {
Time.availableNodes = 0;
TT.clear();
Threads.clear();
- Tablebases::init(Options["SyzygyPath"]); // Free up mapped files
+ Tablebases::init(Options["SyzygyPath"]); // Free mapped files
}
-/// MainThread::search() is called by the main thread when the program receives
-/// the UCI 'go' command. It searches from the root position and outputs the "bestmove".
+/// MainThread::search() is started when the program receives the UCI 'go'
+/// command. It searches from the root position and outputs the "bestmove".
void MainThread::search() {
@@ -217,8 +191,11 @@ void MainThread::search() {
else
{
for (Thread* th : Threads)
+ {
+ th->bestMoveChanges = 0;
if (th != this)
th->start_searching();
+ }
Thread::search(); // Let's start searching!
}
@@ -246,8 +223,9 @@ void MainThread::search() {
if (Limits.npmsec)
Time.availableNodes += Limits.inc[us] - Threads.nodes_searched();
- // Check if there are threads with a better score than main thread
Thread* bestThread = this;
+
+ // Check if there are threads with a better score than main thread
if ( Options["MultiPV"] == 1
&& !Limits.depth
&& !Skill(Options["Skill Level"]).enabled()
@@ -258,27 +236,23 @@ void MainThread::search() {
// Find out minimum score and reset votes for moves which can be voted
for (Thread* th: Threads)
- {
minScore = std::min(minScore, th->rootMoves[0].score);
- votes[th->rootMoves[0].pv[0]] = 0;
- }
// Vote according to score and depth
- auto square = [](int64_t x) { return x * x; };
for (Thread* th : Threads)
- votes[th->rootMoves[0].pv[0]] += 200 + (square(th->rootMoves[0].score - minScore + 1)
- * int64_t(th->completedDepth));
+ {
+ int64_t s = th->rootMoves[0].score - minScore + 1;
+ votes[th->rootMoves[0].pv[0]] += 200 + s * s * int(th->completedDepth);
+ }
// Select best thread
- int64_t bestVote = votes[this->rootMoves[0].pv[0]];
+ auto bestVote = votes[this->rootMoves[0].pv[0]];
for (Thread* th : Threads)
- {
if (votes[th->rootMoves[0].pv[0]] > bestVote)
{
bestVote = votes[th->rootMoves[0].pv[0]];
bestThread = th;
}
- }
}
previousScore = bestThread->rootMoves[0].score;
@@ -302,31 +276,27 @@ void MainThread::search() {
void Thread::search() {
- // To allow access to (ss-5) up to (ss+2), the stack must be oversized.
+ // To allow access to (ss-7) up to (ss+2), the stack must be oversized.
// The former is needed to allow update_continuation_histories(ss-1, ...),
- // which accesses its argument at ss-4, also near the root.
+ // which accesses its argument at ss-6, also near the root.
// The latter is needed for statScores and killer initialization.
- Stack stack[MAX_PLY+8], *ss = stack+5;
+ Stack stack[MAX_PLY+10], *ss = stack+7;
Move pv[MAX_PLY+1];
Value bestValue, alpha, beta, delta;
Move lastBestMove = MOVE_NONE;
Depth lastBestMoveDepth = DEPTH_ZERO;
MainThread* mainThread = (this == Threads.main() ? Threads.main() : nullptr);
- double timeReduction = 1.0;
+ double timeReduction = 1, totBestMoveChanges = 0;
Color us = rootPos.side_to_move();
- bool failedLow;
- std::memset(ss-5, 0, 8 * sizeof(Stack));
- for (int i = 5; i > 0; i--)
+ std::memset(ss-7, 0, 10 * sizeof(Stack));
+ for (int i = 7; i > 0; i--)
(ss-i)->continuationHistory = &this->continuationHistory[NO_PIECE][0]; // Use as sentinel
ss->pv = pv;
bestValue = delta = alpha = -VALUE_INFINITE;
beta = VALUE_INFINITE;
- if (mainThread)
- mainThread->bestMoveChanges = 0, failedLow = false;
-
size_t multiPV = Options["MultiPV"];
Skill skill(Options["Skill Level"]);
@@ -347,7 +317,7 @@ void Thread::search() {
: Options["Analysis Contempt"] == "Black" && us == WHITE ? -ct
: ct;
- // In evaluate.cpp the evaluation is from the white point of view
+ // Evaluation score is from the white point of view
contempt = (us == WHITE ? make_score(ct, ct / 2)
: -make_score(ct, ct / 2));
@@ -356,17 +326,9 @@ void Thread::search() {
&& !Threads.stop
&& !(Limits.depth && mainThread && rootDepth / ONE_PLY > Limits.depth))
{
- // Distribute search depths across the helper threads
- if (idx > 0)
- {
- int i = (idx - 1) % 20;
- if (((rootDepth / ONE_PLY + SkipPhase[i]) / SkipSize[i]) % 2)
- continue; // Retry with an incremented rootDepth
- }
-
// Age out PV variability metric
if (mainThread)
- mainThread->bestMoveChanges *= 0.517, failedLow = false;
+ totBestMoveChanges /= 2;
// Save the last iteration's scores before first PV line is searched and
// all the move scores except the (new) PV are set to -VALUE_INFINITE.
@@ -446,7 +408,6 @@ void Thread::search() {
if (mainThread)
{
failedHighCnt = 0;
- failedLow = true;
mainThread->stopOnPonderhit = false;
}
}
@@ -498,19 +459,22 @@ void Thread::search() {
&& !Threads.stop
&& !mainThread->stopOnPonderhit)
{
- double fallingEval = (306 + 119 * failedLow + 6 * (mainThread->previousScore - bestValue)) / 581.0;
- fallingEval = std::max(0.5, std::min(1.5, fallingEval));
+ double fallingEval = (314 + 9 * (mainThread->previousScore - bestValue)) / 581.0;
+ fallingEval = clamp(fallingEval, 0.5, 1.5);
// If the bestMove is stable over several iterations, reduce time accordingly
timeReduction = lastBestMoveDepth + 10 * ONE_PLY < completedDepth ? 1.95 : 1.0;
+ double reduction = std::pow(mainThread->previousTimeReduction, 0.528) / timeReduction;
// Use part of the gained time from a previous stable move for the current move
- double bestMoveInstability = 1.0 + mainThread->bestMoveChanges;
- bestMoveInstability *= std::pow(mainThread->previousTimeReduction, 0.528) / timeReduction;
+ for (Thread* th : Threads)
+ totBestMoveChanges += th->bestMoveChanges;
+
+ double bestMoveInstability = 1 + totBestMoveChanges / Threads.size();
// Stop the search if we have only one legal move, or if available time elapsed
if ( rootMoves.size() == 1
- || Time.elapsed() > Time.optimum() * bestMoveInstability * fallingEval)
+ || Time.elapsed() > Time.optimum() * fallingEval * reduction * bestMoveInstability)
{
// If we are allowed to ponder do not stop the search now but
// keep pondering until the GUI sends "ponderhit" or "stop".
@@ -572,9 +536,9 @@ namespace {
Key posKey;
Move ttMove, move, excludedMove, bestMove;
Depth extension, newDepth;
- Value bestValue, value, ttValue, eval, maxValue, pureStaticEval;
- bool ttHit, pvHit, inCheck, givesCheck, improving;
- bool captureOrPromotion, doFullDepthSearch, moveCountPruning, skipQuiets, ttCapture;
+ Value bestValue, value, ttValue, eval, maxValue;
+ bool ttHit, ttPv, inCheck, givesCheck, improving;
+ bool captureOrPromotion, doFullDepthSearch, moveCountPruning, ttCapture;
Piece movedPiece;
int moveCount, captureCount, quietCount;
@@ -639,7 +603,16 @@ namespace {
ttValue = ttHit ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE;
ttMove = rootNode ? thisThread->rootMoves[thisThread->pvIdx].pv[0]
: ttHit ? tte->move() : MOVE_NONE;
- pvHit = (ttHit && tte->pv_hit()) || (PvNode && depth > 4 * ONE_PLY);
+ ttPv = (ttHit && tte->is_pv()) || (PvNode && depth > 4 * ONE_PLY);
+
+ // if position has been searched at higher depths and we are shuffling, return value_draw
+ if (pos.rule50_count() > 36
+ && ss->ply > 36
+ && depth < 3 * ONE_PLY
+ && ttHit
+ && tte->depth() > depth
+ && pos.count() > 0)
+ return VALUE_DRAW;
// At non-PV nodes we check for an early TT cutoff
if ( !PvNode
@@ -706,7 +679,7 @@ namespace {
if ( b == BOUND_EXACT
|| (b == BOUND_LOWER ? value >= beta : value <= alpha))
{
- tte->save(posKey, value_to_tt(value, ss->ply), pvHit, b,
+ tte->save(posKey, value_to_tt(value, ss->ply), ttPv, b,
std::min(DEPTH_MAX - ONE_PLY, depth + 6 * ONE_PLY),
MOVE_NONE, VALUE_NONE);
@@ -727,16 +700,16 @@ namespace {
// Step 6. Static evaluation of the position
if (inCheck)
{
- ss->staticEval = eval = pureStaticEval = VALUE_NONE;
+ ss->staticEval = eval = VALUE_NONE;
improving = false;
goto moves_loop; // Skip early pruning when in check
}
else if (ttHit)
{
// Never assume anything on values stored in TT
- ss->staticEval = eval = pureStaticEval = tte->eval();
+ ss->staticEval = eval = tte->eval();
if (eval == VALUE_NONE)
- ss->staticEval = eval = pureStaticEval = evaluate(pos);
+ ss->staticEval = eval = evaluate(pos);
// Can ttValue be used as a better position evaluation?
if ( ttValue != VALUE_NONE
@@ -749,13 +722,12 @@ namespace {
{
int bonus = -(ss-1)->statScore / 512;
- pureStaticEval = evaluate(pos);
- ss->staticEval = eval = pureStaticEval + bonus;
+ ss->staticEval = eval = evaluate(pos) + bonus;
}
else
- ss->staticEval = eval = pureStaticEval = -(ss-1)->staticEval + 2 * Eval::Tempo;
+ ss->staticEval = eval = -(ss-1)->staticEval + 2 * Eval::Tempo;
- tte->save(posKey, VALUE_NONE, pvHit, BOUND_NONE, DEPTH_NONE, MOVE_NONE, pureStaticEval);
+ tte->save(posKey, VALUE_NONE, ttPv, BOUND_NONE, DEPTH_NONE, MOVE_NONE, eval);
}
// Step 7. Razoring (~2 Elo)
@@ -779,7 +751,7 @@ namespace {
&& (ss-1)->currentMove != MOVE_NULL
&& (ss-1)->statScore < 23200
&& eval >= beta
- && pureStaticEval >= beta - 36 * depth / ONE_PLY + 225
+ && ss->staticEval >= beta - 36 * depth / ONE_PLY + 225
&& !excludedMove
&& pos.non_pawn_material(us)
&& (ss->ply >= thisThread->nmpMinPly || us != thisThread->nmpColor))
@@ -835,7 +807,7 @@ namespace {
int probCutCount = 0;
while ( (move = mp.next_move()) != MOVE_NONE
- && probCutCount < 3)
+ && probCutCount < 2 + 2 * cutNode)
if (move != excludedMove && pos.legal(move))
{
probCutCount++;
@@ -850,7 +822,7 @@ namespace {
// Perform a preliminary qsearch to verify that the move holds
value = -qsearch(pos, ss+1, -raisedBeta, -raisedBeta+1);
- // If the qsearch held perform the regular search
+ // If the qsearch held, perform the regular search
if (value >= raisedBeta)
value = -search(pos, ss+1, -raisedBeta, -raisedBeta+1, depth - 4 * ONE_PLY, !cutNode);
@@ -862,8 +834,7 @@ namespace {
}
// Step 11. Internal iterative deepening (~2 Elo)
- if ( depth >= 8 * ONE_PLY
- && !ttMove)
+ if (depth >= 8 * ONE_PLY && !ttMove)
{
search(pos, ss, alpha, beta, depth - 7 * ONE_PLY, cutNode);
@@ -874,7 +845,10 @@ namespace {
moves_loop: // When in check, search starts from here
- const PieceToHistory* contHist[] = { (ss-1)->continuationHistory, (ss-2)->continuationHistory, nullptr, (ss-4)->continuationHistory };
+ const PieceToHistory* contHist[] = { (ss-1)->continuationHistory, (ss-2)->continuationHistory,
+ nullptr, (ss-4)->continuationHistory,
+ nullptr, (ss-6)->continuationHistory };
+
Move countermove = thisThread->counterMoves[pos.piece_on(prevSq)][prevSq];
MovePicker mp(pos, ttMove, depth, &thisThread->mainHistory,
@@ -882,14 +856,14 @@ moves_loop: // When in check, search starts from here
contHist,
countermove,
ss->killers);
- value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc
- skipQuiets = false;
+ value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc
+ moveCountPruning = false;
ttCapture = ttMove && pos.capture_or_promotion(ttMove);
// Step 12. Loop through all pseudo-legal moves until no moves remain
// or a beta cutoff occurs.
- while ((move = mp.next_move(skipQuiets)) != MOVE_NONE)
+ while ((move = mp.next_move(moveCountPruning)) != MOVE_NONE)
{
assert(is_ok(move));
@@ -916,10 +890,7 @@ moves_loop: // When in check, search starts from here
extension = DEPTH_ZERO;
captureOrPromotion = pos.capture_or_promotion(move);
movedPiece = pos.moved_piece(move);
- givesCheck = gives_check(pos, move);
-
- moveCountPruning = depth < 16 * ONE_PLY
- && moveCount >= FutilityMoveCounts[improving][depth / ONE_PLY];
+ givesCheck = pos.gives_check(move);
// Step 13. Extensions (~70 Elo)
@@ -932,12 +903,13 @@ moves_loop: // When in check, search starts from here
&& move == ttMove
&& !rootNode
&& !excludedMove // Avoid recursive singular search
- && ttValue != VALUE_NONE
+ /* && ttValue != VALUE_NONE Already implicit in the next condition */
+ && abs(ttValue) < VALUE_KNOWN_WIN
&& (tte->bound() & BOUND_LOWER)
&& tte->depth() >= depth - 3 * ONE_PLY
&& pos.legal(move))
{
- Value singularBeta = std::max(ttValue - 2 * depth / ONE_PLY, -VALUE_MATE);
+ Value singularBeta = ttValue - 2 * depth / ONE_PLY;
ss->excludedMove = move;
value = search(pos, ss, singularBeta - 1, singularBeta, depth / 2, cutNode);
ss->excludedMove = MOVE_NONE;
@@ -959,6 +931,10 @@ moves_loop: // When in check, search starts from here
&& (pos.blockers_for_king(~us) & from_sq(move) || pos.see_ge(move)))
extension = ONE_PLY;
+ // Shuffle extension
+ else if(pos.rule50_count() > 14 && ss->ply > 14 && depth < 3 * ONE_PLY && PvNode)
+ extension = ONE_PLY;
+
// Castling extension
else if (type_of(move) == CASTLING)
extension = ONE_PLY;
@@ -971,16 +947,16 @@ moves_loop: // When in check, search starts from here
&& pos.non_pawn_material(us)
&& bestValue > VALUE_MATED_IN_MAX_PLY)
{
+ // Skip quiet moves if movecount exceeds our FutilityMoveCount threshold
+ moveCountPruning = moveCount >= futility_move_count(improving, depth / ONE_PLY);
+
if ( !captureOrPromotion
&& !givesCheck
&& !pos.advanced_pawn_push(move))
{
// Move count based pruning (~30 Elo)
if (moveCountPruning)
- {
- skipQuiets = true;
continue;
- }
// Reduced depth of the next LMR search
int lmrDepth = std::max(newDepth - reduction(improving, depth, moveCount), DEPTH_ZERO) / ONE_PLY;
@@ -1001,8 +977,7 @@ moves_loop: // When in check, search starts from here
if (!pos.see_ge(move, Value(-29 * lmrDepth * lmrDepth)))
continue;
}
- else if ( !extension // (~20 Elo)
- && !pos.see_ge(move, -PawnValueEg * (depth / ONE_PLY)))
+ else if (!pos.see_ge(move, -PawnValueEg * (depth / ONE_PLY))) // (~20 Elo)
continue;
}
@@ -1032,7 +1007,7 @@ moves_loop: // When in check, search starts from here
Depth r = reduction(improving, depth, moveCount);
// Decrease reduction if position is or has been on the PV
- if (pvHit)
+ if (ttPv)
r -= ONE_PLY;
// Decrease reduction if opponent's move count is high (~10 Elo)
@@ -1129,8 +1104,8 @@ moves_loop: // When in check, search starts from here
// We record how often the best move has been changed in each
// iteration. This information is used for time management: When
// the best move changes frequently, we allocate some more time.
- if (moveCount > 1 && thisThread == Threads.main())
- ++static_cast(thisThread)->bestMoveChanges;
+ if (moveCount > 1)
+ ++thisThread->bestMoveChanges;
}
else
// All other moves but the PV are set to the lowest value: this
@@ -1213,10 +1188,10 @@ moves_loop: // When in check, search starts from here
bestValue = std::min(bestValue, maxValue);
if (!excludedMove)
- tte->save(posKey, value_to_tt(bestValue, ss->ply), pvHit,
+ tte->save(posKey, value_to_tt(bestValue, ss->ply), ttPv,
bestValue >= beta ? BOUND_LOWER :
PvNode && bestMove ? BOUND_EXACT : BOUND_UPPER,
- depth, bestMove, pureStaticEval);
+ depth, bestMove, ss->staticEval);
assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
@@ -1277,7 +1252,7 @@ moves_loop: // When in check, search starts from here
tte = TT.probe(posKey, ttHit);
ttValue = ttHit ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE;
ttMove = ttHit ? tte->move() : MOVE_NONE;
- pvHit = ttHit && tte->pv_hit();
+ pvHit = ttHit && tte->is_pv();
if ( !PvNode
&& ttHit
@@ -1327,7 +1302,9 @@ moves_loop: // When in check, search starts from here
futilityBase = bestValue + 128;
}
- const PieceToHistory* contHist[] = { (ss-1)->continuationHistory, (ss-2)->continuationHistory, nullptr, (ss-4)->continuationHistory };
+ const PieceToHistory* contHist[] = { (ss-1)->continuationHistory, (ss-2)->continuationHistory,
+ nullptr, (ss-4)->continuationHistory,
+ nullptr, (ss-6)->continuationHistory };
// Initialize a MovePicker object for the current position, and prepare
// to search the moves. Because the depth is <= 0 here, only captures,
@@ -1343,7 +1320,7 @@ moves_loop: // When in check, search starts from here
{
assert(is_ok(move));
- givesCheck = gives_check(pos, move);
+ givesCheck = pos.gives_check(move);
moveCount++;
@@ -1477,7 +1454,7 @@ moves_loop: // When in check, search starts from here
void update_continuation_histories(Stack* ss, Piece pc, Square to, int bonus) {
- for (int i : {1, 2, 4})
+ for (int i : {1, 2, 4, 6})
if (is_ok((ss-i)->currentMove))
(*(ss-i)->continuationHistory)[pc][to] << bonus;
}