X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=30f280728e274055d49771ceb2a413d5b91aa9dd;hp=ba1fef4d07e8081a56c73e354c915f8bf037f894;hb=1982fe25f817c29aef9dd156869a53e520ce3629;hpb=acc47e8b79058a06508fee804aa428820e163b8b
diff --git a/src/search.cpp b/src/search.cpp
index ba1fef4d..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
@@ -61,10 +60,6 @@ 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) {
@@ -89,11 +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
@@ -120,13 +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
@@ -174,12 +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() {
@@ -204,8 +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!
}
@@ -233,8 +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()
@@ -285,9 +276,9 @@ 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+10], *ss = stack+7;
Move pv[MAX_PLY+1];
@@ -295,7 +286,7 @@ void Thread::search() {
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();
std::memset(ss-7, 0, 10 * sizeof(Stack));
@@ -306,9 +297,6 @@ void Thread::search() {
bestValue = delta = alpha = -VALUE_INFINITE;
beta = VALUE_INFINITE;
- if (mainThread)
- mainThread->bestMoveChanges = 0;
-
size_t multiPV = Options["MultiPV"];
Skill skill(Options["Skill Level"]);
@@ -329,7 +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));
@@ -338,17 +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;
+ 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.
@@ -479,15 +459,18 @@ void Thread::search() {
&& !Threads.stop
&& !mainThread->stopOnPonderhit)
{
- double fallingEval = (306 + 9 * (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;
+ 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
@@ -553,7 +536,7 @@ namespace {
Key posKey;
Move ttMove, move, excludedMove, bestMove;
Depth extension, newDepth;
- Value bestValue, value, ttValue, eval, maxValue, pureStaticEval;
+ Value bestValue, value, ttValue, eval, maxValue;
bool ttHit, ttPv, inCheck, givesCheck, improving;
bool captureOrPromotion, doFullDepthSearch, moveCountPruning, ttCapture;
Piece movedPiece;
@@ -622,6 +605,15 @@ namespace {
: ttHit ? tte->move() : MOVE_NONE;
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
&& ttHit
@@ -708,16 +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
@@ -730,13 +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, ttPv, 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)
@@ -760,7 +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))
@@ -843,8 +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);
@@ -858,6 +848,7 @@ moves_loop: // When in check, search starts from here
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,
@@ -865,8 +856,8 @@ moves_loop: // When in check, search starts from here
contHist,
countermove,
ss->killers);
- value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc
+ value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc
moveCountPruning = false;
ttCapture = ttMove && pos.capture_or_promotion(ttMove);
@@ -899,7 +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);
+ givesCheck = pos.gives_check(move);
// Step 13. Extensions (~70 Elo)
@@ -940,6 +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;
@@ -953,7 +948,7 @@ moves_loop: // When in check, search starts from here
&& bestValue > VALUE_MATED_IN_MAX_PLY)
{
// Skip quiet moves if movecount exceeds our FutilityMoveCount threshold
- moveCountPruning = moveCount >= futility_move_count(improving,depth / ONE_PLY);
+ moveCountPruning = moveCount >= futility_move_count(improving, depth / ONE_PLY);
if ( !captureOrPromotion
&& !givesCheck
@@ -982,8 +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;
}
@@ -1110,8 +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
@@ -1197,7 +1191,7 @@ moves_loop: // When in check, search starts from here
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);
@@ -1326,7 +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++;