bool RootInTB;
bool UseRule50;
Depth ProbeDepth;
- Value Score;
}
namespace TB = Tablebases;
return Value((175 - 50 * improving) * d / ONE_PLY);
}
+ // Margin for pruning capturing moves: almost linear in depth
+ constexpr int CapturePruneMargin[] = { 0,
+ 1 * PawnValueEg * 1055 / 1000,
+ 2 * PawnValueEg * 1042 / 1000,
+ 3 * PawnValueEg * 963 / 1000,
+ 4 * PawnValueEg * 1038 / 1000,
+ 5 * PawnValueEg * 950 / 1000,
+ 6 * PawnValueEg * 930 / 1000
+ };
+
// Futility and reductions lookup tables, initialized at startup
int FutilityMoveCounts[2][16]; // [improving][depth]
int Reductions[2][2][64][64]; // [pv][improving][depth][moveNumber]
// History and stats update bonus, based on depth
int stat_bonus(Depth depth) {
int d = depth / ONE_PLY;
- return d > 17 ? 0 : d * d + 2 * d - 2;
+ return d > 17 ? 0 : 32 * d * d + 64 * d - 64;
}
// Skill structure is used to implement strength limit
};
template <NodeType NT>
- Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode, bool skipEarlyPruning);
+ Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode);
template <NodeType NT>
Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth = DEPTH_ZERO);
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 && Reductions[NonPV][imp][d][mc] >= 2)
+ if (!imp && r > 1.0)
Reductions[NonPV][imp][d][mc]++;
}
multiPV = std::min(multiPV, rootMoves.size());
- int ct = Options["Contempt"] * PawnValueEg / 100; // From centipawns
- Eval::Contempt = (us == WHITE ? make_score(ct, ct / 2)
- : -make_score(ct, ct / 2));
+ int ct = int(Options["Contempt"]) * PawnValueEg / 100; // From centipawns
+
+ // In analysis mode, adjust contempt in accordance with user preference
+ if (Limits.infinite || Options["UCI_AnalyseMode"])
+ ct = Options["Analysis Contempt"] == "Off" ? 0
+ : Options["Analysis Contempt"] == "Both" ? ct
+ : Options["Analysis Contempt"] == "White" && us == BLACK ? -ct
+ : Options["Analysis Contempt"] == "Black" && us == WHITE ? -ct
+ : ct;
+
+ // In evaluate.cpp the evaluation is from the white point of view
+ contempt = (us == WHITE ? make_score(ct, ct / 2)
+ : -make_score(ct, ct / 2));
// Iterative deepening loop until requested to stop or the target depth is reached
while ( (rootDepth += ONE_PLY) < DEPTH_MAX
for (RootMove& rm : rootMoves)
rm.previousScore = rm.score;
+ size_t PVFirst = 0;
+ PVLast = 0;
+
// MultiPV loop. We perform a full root search for each PV line
for (PVIdx = 0; PVIdx < multiPV && !Threads.stop; ++PVIdx)
{
+ if (PVIdx == PVLast)
+ {
+ PVFirst = PVLast;
+ for (PVLast++; PVLast < rootMoves.size(); PVLast++)
+ if (rootMoves[PVLast].TBRank != rootMoves[PVFirst].TBRank)
+ break;
+ }
+
// Reset UCI info selDepth for each depth and each PV line
selDepth = 0;
// Reset aspiration window starting size
if (rootDepth >= 5 * ONE_PLY)
{
+ Value previousScore = rootMoves[PVIdx].previousScore;
delta = Value(18);
- alpha = std::max(rootMoves[PVIdx].previousScore - delta,-VALUE_INFINITE);
- beta = std::min(rootMoves[PVIdx].previousScore + delta, VALUE_INFINITE);
+ alpha = std::max(previousScore - delta,-VALUE_INFINITE);
+ beta = std::min(previousScore + delta, VALUE_INFINITE);
- ct = Options["Contempt"] * PawnValueEg / 100; // From centipawns
+ // Adjust contempt based on root move's previousScore (dynamic contempt)
+ int dct = ct + 88 * previousScore / (abs(previousScore) + 200);
- // Adjust contempt based on current bestValue (dynamic contempt)
- ct += int(std::round(48 * atan(float(bestValue) / 128)));
-
- Eval::Contempt = (us == WHITE ? make_score(ct, ct / 2)
- : -make_score(ct, ct / 2));
+ contempt = (us == WHITE ? make_score(dct, dct / 2)
+ : -make_score(dct, dct / 2));
}
// Start with a small aspiration window and, in the case of a fail
// high/low anymore.
while (true)
{
- bestValue = ::search<PV>(rootPos, ss, alpha, beta, rootDepth, false, false);
+ bestValue = ::search<PV>(rootPos, ss, alpha, beta, rootDepth, false);
// Bring the best move to the front. It is critical that sorting
// is done with a stable algorithm because all the values but the
// and we want to keep the same order for all the moves except the
// new PV that goes to the front. Note that in case of MultiPV
// search the already searched PV lines are preserved.
- std::stable_sort(rootMoves.begin() + PVIdx, rootMoves.end());
+ std::stable_sort(rootMoves.begin() + PVIdx, rootMoves.begin() + PVLast);
// If search has been stopped, we break immediately. Sorting is
// safe because RootMoves is still valid, although it refers to
}
// Sort the PV lines searched so far and update the GUI
- std::stable_sort(rootMoves.begin(), rootMoves.begin() + PVIdx + 1);
+ std::stable_sort(rootMoves.begin() + PVFirst, rootMoves.begin() + PVIdx + 1);
if ( mainThread
&& (Threads.stop || PVIdx + 1 == multiPV || Time.elapsed() > 3000))
// search<>() is the main search function for both PV and non-PV nodes
template <NodeType NT>
- Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode, bool skipEarlyPruning) {
+ Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode) {
// Use quiescence search when needed
if (depth < ONE_PLY)
Move ttMove, move, excludedMove, bestMove;
Depth extension, newDepth;
Value bestValue, value, ttValue, eval, maxValue;
- bool ttHit, inCheck, givesCheck, singularExtensionNode, improving;
+ bool ttHit, inCheck, givesCheck, improving;
bool captureOrPromotion, doFullDepthSearch, moveCountPruning, skipQuiets, ttCapture, pvExact;
Piece movedPiece;
int moveCount, captureCount, quietCount;
}
}
- // Step 6. Evaluate the position statically
+ // Step 6. Static evaluation of the position
if (inCheck)
{
ss->staticEval = eval = VALUE_NONE;
improving = false;
- goto moves_loop;
+ goto moves_loop; // Skip early pruning when in check
}
else if (ttHit)
{
ss->staticEval, TT.generation());
}
- improving = ss->staticEval >= (ss-2)->staticEval
- ||(ss-2)->staticEval == VALUE_NONE;
-
- if (skipEarlyPruning || !pos.non_pawn_material(pos.side_to_move()))
- goto moves_loop;
-
- // Step 7. Razoring (skipped when in check)
+ // Step 7. Razoring (~2 Elo)
if ( !PvNode
&& depth < 3 * ONE_PLY
&& eval <= alpha - RazorMargin[depth / ONE_PLY])
return v;
}
- // Step 8. Futility pruning: child node (skipped when in check)
+ improving = ss->staticEval >= (ss-2)->staticEval
+ || (ss-2)->staticEval == VALUE_NONE;
+
+ // Step 8. Futility pruning: child node (~30 Elo)
if ( !rootNode
&& depth < 7 * ONE_PLY
&& eval - futility_margin(depth, improving) >= beta
&& eval < VALUE_KNOWN_WIN) // Do not return unproven wins
return eval;
- // Step 9. Null move search with verification search
+ // Step 9. Null move search with verification search (~40 Elo)
if ( !PvNode
+ && (ss-1)->currentMove != MOVE_NULL
+ && (ss-1)->statScore < 22500
&& eval >= beta
&& ss->staticEval >= beta - 36 * depth / ONE_PLY + 225
+ && !ss->excludedMove
+ && pos.non_pawn_material(pos.side_to_move())
&& (ss->ply >= thisThread->nmp_ply || ss->ply % 2 != thisThread->nmp_odd))
{
assert(eval - beta >= 0);
pos.do_null_move(st);
- Value nullValue = -search<NonPV>(pos, ss+1, -beta, -beta+1, depth-R, !cutNode, true);
+ Value nullValue = -search<NonPV>(pos, ss+1, -beta, -beta+1, depth-R, !cutNode);
pos.undo_null_move();
thisThread->nmp_ply = ss->ply + 3 * (depth-R) / 4;
thisThread->nmp_odd = ss->ply % 2;
- Value v = search<NonPV>(pos, ss, beta-1, beta, depth-R, false, true);
+ Value v = search<NonPV>(pos, ss, beta-1, beta, depth-R, false);
thisThread->nmp_odd = thisThread->nmp_ply = 0;
}
}
- // Step 10. ProbCut (skipped when in check)
+ // Step 10. ProbCut (~10 Elo)
// If we have a good enough capture and a reduced search returns a value
// much above beta, we can (almost) safely prune the previous move.
if ( !PvNode
&& depth >= 5 * ONE_PLY
&& abs(beta) < VALUE_MATE_IN_MAX_PLY)
{
- assert(is_ok((ss-1)->currentMove));
-
Value rbeta = std::min(beta + 216 - 48 * improving, VALUE_INFINITE);
MovePicker mp(pos, ttMove, rbeta - ss->staticEval, &thisThread->captureHistory);
int probCutCount = 0;
// If the qsearch held perform the regular search
if (value >= rbeta)
- value = -search<NonPV>(pos, ss+1, -rbeta, -rbeta+1, depth - 4 * ONE_PLY, !cutNode, false);
+ value = -search<NonPV>(pos, ss+1, -rbeta, -rbeta+1, depth - 4 * ONE_PLY, !cutNode);
pos.undo_move(move);
}
}
- // Step 11. Internal iterative deepening (skipped when in check)
- if ( depth >= 6 * ONE_PLY
- && !ttMove
- && (PvNode || ss->staticEval + 256 >= beta))
+ // Step 11. Internal iterative deepening (~2 Elo)
+ if ( depth >= 8 * ONE_PLY
+ && !ttMove)
{
Depth d = 3 * depth / 4 - 2 * ONE_PLY;
- search<NT>(pos, ss, alpha, beta, d, cutNode, true);
+ search<NT>(pos, ss, alpha, beta, d, cutNode);
tte = TT.probe(posKey, ttHit);
ttValue = ttHit ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE;
const PieceToHistory* contHist[] = { (ss-1)->contHistory, (ss-2)->contHistory, nullptr, (ss-4)->contHistory };
Move countermove = thisThread->counterMoves[pos.piece_on(prevSq)][prevSq];
- MovePicker mp(pos, ttMove, depth, &thisThread->mainHistory, &thisThread->captureHistory, contHist, countermove, ss->killers);
+ MovePicker mp(pos, ttMove, depth, &thisThread->mainHistory,
+ &thisThread->captureHistory,
+ contHist,
+ countermove,
+ ss->killers);
value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc
- singularExtensionNode = !rootNode
- && depth >= 8 * ONE_PLY
- && ttMove != MOVE_NONE
- && ttValue != VALUE_NONE
- && !excludedMove // Recursive singular search is not allowed
- && (tte->bound() & BOUND_LOWER)
- && tte->depth() >= depth - 3 * ONE_PLY;
skipQuiets = false;
ttCapture = false;
pvExact = PvNode && ttHit && tte->bound() == BOUND_EXACT;
// At root obey the "searchmoves" option and skip moves not listed in Root
// Move List. As a consequence any illegal move is also skipped. In MultiPV
- // mode we also skip PV moves which have been already searched.
+ // mode we also skip PV moves which have been already searched and those
+ // of lower "TB rank" if we are in a TB root position.
if (rootNode && !std::count(thisThread->rootMoves.begin() + thisThread->PVIdx,
- thisThread->rootMoves.end(), move))
+ thisThread->rootMoves.begin() + thisThread->PVLast, move))
continue;
ss->moveCount = ++moveCount;
moveCountPruning = depth < 16 * ONE_PLY
&& moveCount >= FutilityMoveCounts[improving][depth / ONE_PLY];
- // Step 13. Extensions
+ // Step 13. Extensions (~70 Elo)
- // Singular extension search. If all moves but one fail low on a search
- // of (alpha-s, beta-s), and just one fails high on (alpha, beta), then
- // that move is singular and should be extended. To verify this we do a
- // reduced search on on all the other moves but the ttMove and if the
+ // Singular extension search (~60 Elo). If all moves but one fail low on a
+ // search of (alpha-s, beta-s), and just one fails high on (alpha, beta),
+ // then that move is singular and should be extended. To verify this we do
+ // a reduced search on on all the other moves but the ttMove and if the
// result is lower than ttValue minus a margin then we will extend the ttMove.
- if ( singularExtensionNode
+ if ( depth >= 8 * ONE_PLY
&& move == ttMove
+ && !rootNode
+ && !excludedMove // Recursive singular search is not allowed
+ && ttValue != VALUE_NONE
+ && (tte->bound() & BOUND_LOWER)
+ && tte->depth() >= depth - 3 * ONE_PLY
&& pos.legal(move))
{
Value rBeta = std::max(ttValue - 2 * depth / ONE_PLY, -VALUE_MATE);
ss->excludedMove = move;
- value = search<NonPV>(pos, ss, rBeta - 1, rBeta, depth / 2, cutNode, true);
+ value = search<NonPV>(pos, ss, rBeta - 1, rBeta, depth / 2, cutNode);
ss->excludedMove = MOVE_NONE;
if (value < rBeta)
extension = ONE_PLY;
}
- else if ( givesCheck // Check extension
+ else if ( givesCheck // Check extension (~2 Elo)
&& !moveCountPruning
&& pos.see_ge(move))
extension = ONE_PLY;
// Calculate new depth for this move
newDepth = depth - ONE_PLY + extension;
- // Step 14. Pruning at shallow depth
+ // Step 14. Pruning at shallow depth (~170 Elo)
if ( !rootNode
&& pos.non_pawn_material(pos.side_to_move())
&& bestValue > VALUE_MATED_IN_MAX_PLY)
&& !givesCheck
&& (!pos.advanced_pawn_push(move) || pos.non_pawn_material() >= Value(5000)))
{
- // Move count based pruning
+ // Move count based pruning (~30 Elo)
if (moveCountPruning)
{
skipQuiets = true;
// Reduced depth of the next LMR search
int lmrDepth = std::max(newDepth - reduction<PvNode>(improving, depth, moveCount), DEPTH_ZERO) / ONE_PLY;
- // Countermoves based pruning
+ // Countermoves based pruning (~20 Elo)
if ( lmrDepth < 3
&& (*contHist[0])[movedPiece][to_sq(move)] < CounterMovePruneThreshold
&& (*contHist[1])[movedPiece][to_sq(move)] < CounterMovePruneThreshold)
continue;
- // Futility pruning: parent node
+ // Futility pruning: parent node (~2 Elo)
if ( lmrDepth < 7
&& !inCheck
&& ss->staticEval + 256 + 200 * lmrDepth <= alpha)
continue;
- // Prune moves with negative SEE
+ // Prune moves with negative SEE (~10 Elo)
if ( lmrDepth < 8
&& !pos.see_ge(move, Value(-35 * lmrDepth * lmrDepth)))
continue;
}
- else if ( depth < 7 * ONE_PLY
+ else if ( depth < 7 * ONE_PLY // (~20 Elo)
&& !extension
- && !pos.see_ge(move, -PawnValueEg * (depth / ONE_PLY)))
+ && !pos.see_ge(move, -Value(CapturePruneMargin[depth / ONE_PLY])))
continue;
}
{
Depth r = reduction<PvNode>(improving, depth, moveCount);
- if (captureOrPromotion)
+ if (captureOrPromotion) // (~5 Elo)
r -= r ? ONE_PLY : DEPTH_ZERO;
else
{
- // Decrease reduction if opponent's move count is high
+ // Decrease reduction if opponent's move count is high (~5 Elo)
if ((ss-1)->moveCount > 15)
r -= ONE_PLY;
- // Decrease reduction for exact PV nodes
+ // Decrease reduction for exact PV nodes (~0 Elo)
if (pvExact)
r -= ONE_PLY;
- // Increase reduction if ttMove is a capture
+ // Increase reduction if ttMove is a capture (~0 Elo)
if (ttCapture)
r += ONE_PLY;
- // Increase reduction for cut nodes
+ // Increase reduction for cut nodes (~5 Elo)
if (cutNode)
r += 2 * ONE_PLY;
// Decrease reduction for moves that escape a capture. Filter out
// castling moves, because they are coded as "king captures rook" and
- // hence break make_move().
+ // hence break make_move(). (~5 Elo)
else if ( type_of(move) == NORMAL
&& !pos.see_ge(make_move(to_sq(move), from_sq(move))))
r -= 2 * ONE_PLY;
+ (*contHist[3])[movedPiece][to_sq(move)]
- 4000;
- // Decrease/increase reduction by comparing opponent's stat score
+ // Decrease/increase reduction by comparing opponent's stat score (~10 Elo)
if (ss->statScore >= 0 && (ss-1)->statScore < 0)
r -= ONE_PLY;
else if ((ss-1)->statScore >= 0 && ss->statScore < 0)
r += ONE_PLY;
- // Decrease/increase reduction for moves with a good/bad history
+ // Decrease/increase reduction for moves with a good/bad history (~30 Elo)
r = std::max(DEPTH_ZERO, (r / ONE_PLY - ss->statScore / 20000) * ONE_PLY);
}
Depth d = std::max(newDepth - r, ONE_PLY);
- value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, true, false);
+ value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, true);
doFullDepthSearch = (value > alpha && d != newDepth);
}
// Step 17. Full depth search when LMR is skipped or fails high
if (doFullDepthSearch)
- value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, !cutNode, false);
+ value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, !cutNode);
// For PV nodes only, do a full PV search on the first move or after a fail
// high (in the latter case search only if value < beta), otherwise let the
(ss+1)->pv = pv;
(ss+1)->pv[0] = MOVE_NONE;
- value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, false, false);
+ value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, false);
}
// Step 18. Undo move
else
{
assert(value >= beta); // Fail high
+ ss->statScore = std::max(ss->statScore, 0);
break;
}
}
// to search the moves. Because the depth is <= 0 here, only captures,
// queen promotions and checks (only if depth >= DEPTH_QS_CHECKS) will
// be generated.
- MovePicker mp(pos, ttMove, depth, &pos.this_thread()->mainHistory, &pos.this_thread()->captureHistory, to_sq((ss-1)->currentMove));
+ MovePicker mp(pos, ttMove, depth, &pos.this_thread()->mainHistory,
+ &pos.this_thread()->captureHistory,
+ to_sq((ss-1)->currentMove));
// Loop through the moves until no moves remain or a beta cutoff occurs
while ((move = mp.next_move()) != MOVE_NONE)
static TimePoint lastInfoTime = now();
- int elapsed = Time.elapsed();
+ TimePoint elapsed = Time.elapsed();
TimePoint tick = Limits.startTime + elapsed;
if (tick - lastInfoTime >= 1000)
string UCI::pv(const Position& pos, Depth depth, Value alpha, Value beta) {
std::stringstream ss;
- int elapsed = Time.elapsed() + 1;
+ TimePoint elapsed = Time.elapsed() + 1;
const RootMoves& rootMoves = pos.this_thread()->rootMoves;
size_t PVIdx = pos.this_thread()->PVIdx;
size_t multiPV = std::min((size_t)Options["MultiPV"], rootMoves.size());
Value v = updated ? rootMoves[i].score : rootMoves[i].previousScore;
bool tb = TB::RootInTB && abs(v) < VALUE_MATE - MAX_PLY;
- v = tb ? TB::Score : v;
+ v = tb ? rootMoves[i].TBScore : v;
if (ss.rdbuf()->in_avail()) // Not at first line
ss << "\n";
return pv.size() > 1;
}
-
-void Tablebases::filter_root_moves(Position& pos, Search::RootMoves& rootMoves) {
+void Tablebases::rank_root_moves(Position& pos, Search::RootMoves& rootMoves) {
RootInTB = false;
- UseRule50 = Options["Syzygy50MoveRule"];
- ProbeDepth = Options["SyzygyProbeDepth"] * ONE_PLY;
- Cardinality = Options["SyzygyProbeLimit"];
+ UseRule50 = bool(Options["Syzygy50MoveRule"]);
+ ProbeDepth = int(Options["SyzygyProbeDepth"]) * ONE_PLY;
+ Cardinality = int(Options["SyzygyProbeLimit"]);
+ bool dtz_available = true;
- // Skip TB probing when no TB found: !TBLargest -> !TB::Cardinality
+ // Tables with fewer pieces than SyzygyProbeLimit are searched with
+ // ProbeDepth == DEPTH_ZERO
if (Cardinality > MaxCardinality)
{
Cardinality = MaxCardinality;
ProbeDepth = DEPTH_ZERO;
}
- if (Cardinality < popcount(pos.pieces()) || pos.can_castle(ANY_CASTLING))
- return;
-
- // Don't filter any moves if the user requested analysis on multiple
- if (Options["MultiPV"] != 1)
- return;
+ if (Cardinality >= popcount(pos.pieces()) && !pos.can_castle(ANY_CASTLING))
+ {
+ // Rank moves using DTZ tables
+ RootInTB = root_probe(pos, rootMoves);
- // If the current root position is in the tablebases, then RootMoves
- // contains only moves that preserve the draw or the win.
- RootInTB = root_probe(pos, rootMoves, TB::Score);
+ if (!RootInTB)
+ {
+ // DTZ tables are missing; try to rank moves using WDL tables
+ dtz_available = false;
+ RootInTB = root_probe_wdl(pos, rootMoves);
+ }
+ }
if (RootInTB)
- Cardinality = 0; // Do not probe tablebases during the search
-
- else // If DTZ tables are missing, use WDL tables as a fallback
{
- // Filter out moves that do not preserve the draw or the win.
- RootInTB = root_probe_wdl(pos, rootMoves, TB::Score);
+ // Sort moves according to TB rank
+ std::sort(rootMoves.begin(), rootMoves.end(),
+ [](const RootMove &a, const RootMove &b) { return a.TBRank > b.TBRank; } );
- // Only probe during search if winning
- if (RootInTB && TB::Score <= VALUE_DRAW)
+ // Probe during search only if DTZ is not available and we are winning
+ if (dtz_available || rootMoves[0].TBScore <= VALUE_DRAW)
Cardinality = 0;
}
-
- if (RootInTB && !UseRule50)
- TB::Score = TB::Score > VALUE_DRAW ? VALUE_MATE - MAX_PLY - 1
- : TB::Score < VALUE_DRAW ? -VALUE_MATE + MAX_PLY + 1
- : VALUE_DRAW;
-
- // Since root_probe() and root_probe_wdl() dirty the root move scores,
- // we reset them to -VALUE_INFINITE
- for (RootMove& rm : rootMoves)
- rm.score = -VALUE_INFINITE;
+ else
+ {
+ // Assign the same rank to all moves
+ for (auto& m : rootMoves)
+ m.TBRank = 0;
+ }
}
projects / stockfish / blobdiff