#include <sstream>
#include "evaluate.h"
+#include "misc.h"
#include "movegen.h"
#include "movepick.h"
-#include "rkiss.h"
#include "search.h"
#include "timeman.h"
#include "thread.h"
#include "tt.h"
#include "uci.h"
+#include "syzygy/tbprobe.h"
namespace Search {
volatile SignalsType Signals;
LimitsType Limits;
- std::vector<RootMove> RootMoves;
+ RootMoveVector RootMoves;
Position RootPos;
Time::point SearchTime;
StateStackPtr SetupStates;
}
+namespace Tablebases {
+
+ int Cardinality;
+ uint64_t Hits;
+ bool RootInTB;
+ bool UseRule50;
+ Depth ProbeDepth;
+ Value Score;
+}
+
+namespace TB = Tablebases;
+
using std::string;
using Eval::evaluate;
using namespace Search;
void id_loop(Position& pos);
Value value_to_tt(Value v, int ply);
Value value_from_tt(Value v, int ply);
- void update_pv(Move* pv, Move move, Move* child);
+ void update_pv(Move* pv, Move move, Move* childPv);
void update_stats(const Position& pos, Stack* ss, Move move, Depth depth, Move* quiets, int quietsCnt);
string uci_pv(const Position& pos, Depth depth, Value alpha, Value beta);
}
size_t candidates_size() const { return candidates; }
- bool time_to_pick(Depth depth) const { return depth == 1 + level; }
+ bool time_to_pick(Depth depth) const { return depth / ONE_PLY == 1 + level; }
Move pick_move();
int level;
TimeMgr.init(Limits, RootPos.game_ply(), RootPos.side_to_move());
- int cf = Options["Contempt"] * PawnValueEg / 100; // From centipawns
- DrawValue[ RootPos.side_to_move()] = VALUE_DRAW - Value(cf);
- DrawValue[~RootPos.side_to_move()] = VALUE_DRAW + Value(cf);
+ int contempt = Options["Contempt"] * PawnValueEg / 100; // From centipawns
+ DrawValue[ RootPos.side_to_move()] = VALUE_DRAW - Value(contempt);
+ DrawValue[~RootPos.side_to_move()] = VALUE_DRAW + Value(contempt);
+
+ TB::Hits = 0;
+ TB::RootInTB = false;
+ TB::UseRule50 = Options["Syzygy50MoveRule"];
+ TB::ProbeDepth = Options["SyzygyProbeDepth"] * ONE_PLY;
+ TB::Cardinality = Options["SyzygyProbeLimit"];
+
+ // Skip TB probing when no TB found: !TBLargest -> !TB::Cardinality
+ if (TB::Cardinality > TB::MaxCardinality)
+ {
+ TB::Cardinality = TB::MaxCardinality;
+ TB::ProbeDepth = DEPTH_ZERO;
+ }
if (RootMoves.empty())
{
}
else
{
+ if (TB::Cardinality >= RootPos.count<ALL_PIECES>(WHITE)
+ + RootPos.count<ALL_PIECES>(BLACK))
+ {
+ // If the current root position is in the tablebases then RootMoves
+ // contains only moves that preserve the draw or win.
+ TB::RootInTB = Tablebases::root_probe(RootPos, RootMoves, TB::Score);
+
+ if (TB::RootInTB)
+ TB::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 a draw or win
+ TB::RootInTB = Tablebases::root_probe_wdl(RootPos, RootMoves, TB::Score);
+
+ // Only probe during search if winning
+ if (TB::Score <= VALUE_DRAW)
+ TB::Cardinality = 0;
+ }
+
+ if (TB::RootInTB)
+ {
+ TB::Hits = RootMoves.size();
+
+ if (!TB::UseRule50)
+ TB::Score = TB::Score > VALUE_DRAW ? VALUE_MATE - MAX_PLY - 1
+ : TB::Score < VALUE_DRAW ? -VALUE_MATE + MAX_PLY + 1
+ : VALUE_DRAW;
+ }
+ }
+
for (size_t i = 0; i < Threads.size(); ++i)
Threads[i]->maxPly = 0;
RootPos.this_thread()->wait_for(Signals.stop);
}
- sync_cout << "bestmove " << UCI::format_move(RootMoves[0].pv[0], RootPos.is_chess960())
- << " ponder " << UCI::format_move(RootMoves[0].pv[1], RootPos.is_chess960())
- << sync_endl;
+ sync_cout << "bestmove " << UCI::format_move(RootMoves[0].pv[0], RootPos.is_chess960());
+
+ if (RootMoves[0].pv.size() > 1)
+ std::cout << " ponder " << UCI::format_move(RootMoves[0].pv[1], RootPos.is_chess960());
+
+ std::cout << sync_endl;
}
// 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.
for (size_t i = 0; i < RootMoves.size(); ++i)
- RootMoves[i].prevScore = RootMoves[i].score;
+ RootMoves[i].previousScore = RootMoves[i].score;
// MultiPV loop. We perform a full root search for each PV line
for (PVIdx = 0; PVIdx < std::min(multiPV, RootMoves.size()) && !Signals.stop; ++PVIdx)
if (depth >= 5 * ONE_PLY)
{
delta = Value(16);
- alpha = std::max(RootMoves[PVIdx].prevScore - delta,-VALUE_INFINITE);
- beta = std::min(RootMoves[PVIdx].prevScore + delta, VALUE_INFINITE);
+ alpha = std::max(RootMoves[PVIdx].previousScore - delta,-VALUE_INFINITE);
+ beta = std::min(RootMoves[PVIdx].previousScore + delta, VALUE_INFINITE);
}
// Start with a small aspiration window and, in the case of a fail
Move pv[MAX_PLY+1], quietsSearched[64];
StateInfo st;
- const TTEntry *tte;
+ TTEntry* tte;
+ bool ttHit;
SplitPoint* splitPoint;
Key posKey;
Move ttMove, move, excludedMove, bestMove;
- Depth ext, newDepth, predictedDepth;
+ Depth extension, newDepth, predictedDepth;
Value bestValue, value, ttValue, eval, nullValue, futilityValue;
bool inCheck, givesCheck, singularExtensionNode, improving;
bool captureOrPromotion, dangerous, doFullDepthSearch;
bestMove = splitPoint->bestMove;
bestValue = splitPoint->bestValue;
tte = NULL;
+ ttHit = false;
ttMove = excludedMove = MOVE_NONE;
ttValue = VALUE_NONE;
assert(0 <= ss->ply && ss->ply < MAX_PLY);
ss->currentMove = ss->ttMove = (ss+1)->excludedMove = bestMove = MOVE_NONE;
- (ss+1)->skipNullMove = false; (ss+1)->reduction = DEPTH_ZERO;
+ (ss+1)->skipEarlyPruning = false; (ss+1)->reduction = DEPTH_ZERO;
(ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE;
// Step 4. Transposition table lookup
// TT value, so we use a different position key in case of an excluded move.
excludedMove = ss->excludedMove;
posKey = excludedMove ? pos.exclusion_key() : pos.key();
- tte = TT.probe(posKey);
- ss->ttMove = ttMove = RootNode ? RootMoves[PVIdx].pv[0] : tte ? tte->move() : MOVE_NONE;
- ttValue = tte ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE;
+ tte = TT.probe(posKey, ttHit);
+ ss->ttMove = ttMove = RootNode ? RootMoves[PVIdx].pv[0] : ttHit ? tte->move() : MOVE_NONE;
+ ttValue = ttHit ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE;
// At non-PV nodes we check for a fail high/low. We don't probe at PV nodes
if ( !PvNode
- && tte
+ && ttHit
&& tte->depth() >= depth
&& ttValue != VALUE_NONE // Only in case of TT access race
&& (ttValue >= beta ? (tte->bound() & BOUND_LOWER)
return ttValue;
}
+ // Step 4a. Tablebase probe
+ if (!RootNode && TB::Cardinality)
+ {
+ int piecesCnt = pos.count<ALL_PIECES>(WHITE) + pos.count<ALL_PIECES>(BLACK);
+
+ if ( piecesCnt <= TB::Cardinality
+ && (piecesCnt < TB::Cardinality || depth >= TB::ProbeDepth)
+ && pos.rule50_count() == 0)
+ {
+ int found, v = Tablebases::probe_wdl(pos, &found);
+
+ if (found)
+ {
+ TB::Hits++;
+
+ int drawScore = TB::UseRule50 ? 1 : 0;
+
+ value = v < -drawScore ? -VALUE_MATE + MAX_PLY + ss->ply
+ : v > drawScore ? VALUE_MATE - MAX_PLY - ss->ply
+ : VALUE_DRAW + 2 * v * drawScore;
+
+ tte->save(posKey, value_to_tt(value, ss->ply), BOUND_EXACT,
+ std::min(DEPTH_MAX - ONE_PLY, depth + 6 * ONE_PLY),
+ MOVE_NONE, VALUE_NONE, TT.get_generation());
+
+ return value;
+ }
+ }
+ }
+
// Step 5. Evaluate the position statically and update parent's gain statistics
if (inCheck)
{
goto moves_loop;
}
- else if (tte)
+ else if (ttHit)
{
// Never assume anything on values stored in TT
if ((ss->staticEval = eval = tte->eval_value()) == VALUE_NONE)
eval = ss->staticEval =
(ss-1)->currentMove != MOVE_NULL ? evaluate(pos) : -(ss-1)->staticEval + 2 * Eval::Tempo;
- TT.store(posKey, VALUE_NONE, BOUND_NONE, DEPTH_NONE, MOVE_NONE, ss->staticEval);
+ tte->save(posKey, VALUE_NONE, BOUND_NONE, DEPTH_NONE, MOVE_NONE, ss->staticEval, TT.get_generation());
}
+ if (ss->skipEarlyPruning)
+ goto moves_loop;
+
if ( !pos.captured_piece_type()
&& ss->staticEval != VALUE_NONE
&& (ss-1)->staticEval != VALUE_NONE
// Step 7. Futility pruning: child node (skipped when in check)
if ( !PvNode
- && !ss->skipNullMove
&& depth < 7 * ONE_PLY
&& eval - futility_margin(depth) >= beta
&& eval < VALUE_KNOWN_WIN // Do not return unproven wins
// Step 8. Null move search with verification search (is omitted in PV nodes)
if ( !PvNode
- && !ss->skipNullMove
&& depth >= 2 * ONE_PLY
&& eval >= beta
&& pos.non_pawn_material(pos.side_to_move()))
assert(eval - beta >= 0);
// Null move dynamic reduction based on depth and value
- Depth R = (3 + depth / 4 + std::min(int(eval - beta) / PawnValueMg, 3)) * ONE_PLY;
+ Depth R = (3 + depth / 4 + std::min((eval - beta) / PawnValueMg, 3)) * ONE_PLY;
pos.do_null_move(st);
- (ss+1)->skipNullMove = true;
+ (ss+1)->skipEarlyPruning = true;
nullValue = depth-R < ONE_PLY ? -qsearch<NonPV, false>(pos, ss+1, -beta, -beta+1, DEPTH_ZERO)
: - search<NonPV, false>(pos, ss+1, -beta, -beta+1, depth-R, !cutNode);
- (ss+1)->skipNullMove = false;
+ (ss+1)->skipEarlyPruning = false;
pos.undo_null_move();
if (nullValue >= beta)
return nullValue;
// Do verification search at high depths
- ss->skipNullMove = true;
+ ss->skipEarlyPruning = true;
Value v = depth-R < ONE_PLY ? qsearch<NonPV, false>(pos, ss, beta-1, beta, DEPTH_ZERO)
: search<NonPV, false>(pos, ss, beta-1, beta, depth-R, false);
- ss->skipNullMove = false;
+ ss->skipEarlyPruning = false;
if (v >= beta)
return nullValue;
// prune the previous move.
if ( !PvNode
&& depth >= 5 * ONE_PLY
- && !ss->skipNullMove
&& abs(beta) < VALUE_MATE_IN_MAX_PLY)
{
Value rbeta = std::min(beta + 200, VALUE_INFINITE);
&& (PvNode || ss->staticEval + 256 >= beta))
{
Depth d = 2 * (depth - 2 * ONE_PLY) - (PvNode ? DEPTH_ZERO : depth / 2);
- ss->skipNullMove = true;
+ ss->skipEarlyPruning = true;
search<PvNode ? PV : NonPV, false>(pos, ss, alpha, beta, d / 2, true);
- ss->skipNullMove = false;
+ ss->skipEarlyPruning = false;
- tte = TT.probe(posKey);
- ttMove = tte ? tte->move() : MOVE_NONE;
+ tte = TT.probe(posKey, ttHit);
+ ttMove = ttHit ? tte->move() : MOVE_NONE;
}
moves_loop: // When in check and at SpNode search starts from here
Signals.firstRootMove = (moveCount == 1);
if (thisThread == Threads.main() && Time::now() - SearchTime > 3000)
- sync_cout << "info depth " << depth
+ sync_cout << "info depth " << depth / ONE_PLY
<< " currmove " << UCI::format_move(move, pos.is_chess960())
<< " currmovenumber " << moveCount + PVIdx << sync_endl;
}
if (PvNode)
(ss+1)->pv = NULL;
- ext = DEPTH_ZERO;
+ extension = DEPTH_ZERO;
captureOrPromotion = pos.capture_or_promotion(move);
givesCheck = type_of(move) == NORMAL && !ci.dcCandidates
// Step 12. Extend checks
if (givesCheck && pos.see_sign(move) >= VALUE_ZERO)
- ext = ONE_PLY;
+ extension = ONE_PLY;
// 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
// ttValue minus a margin then we extend the ttMove.
if ( singularExtensionNode
&& move == ttMove
- && !ext
+ && !extension
&& pos.legal(move, ci.pinned))
{
- Value rBeta = ttValue - int(2 * depth);
+ Value rBeta = ttValue - 2 * depth / ONE_PLY;
ss->excludedMove = move;
- ss->skipNullMove = true;
+ ss->skipEarlyPruning = true;
value = search<NonPV, false>(pos, ss, rBeta - 1, rBeta, depth / 2, cutNode);
- ss->skipNullMove = false;
+ ss->skipEarlyPruning = false;
ss->excludedMove = MOVE_NONE;
if (value < rBeta)
- ext = ONE_PLY;
+ extension = ONE_PLY;
}
// Update the current move (this must be done after singular extension search)
- newDepth = depth - ONE_PLY + ext;
+ newDepth = depth - ONE_PLY + extension;
// Step 13. Pruning at shallow depth (exclude PV nodes)
if ( !PvNode
// parent node fail low with value <= alpha and to try another move.
if (PvNode && (moveCount == 1 || (value > alpha && (RootNode || value < beta))))
{
- pv[0] = MOVE_NONE;
(ss+1)->pv = pv;
+ (ss+1)->pv[0] = MOVE_NONE;
+
value = newDepth < ONE_PLY ?
givesCheck ? -qsearch<PV, true>(pos, ss+1, -beta, -alpha, DEPTH_ZERO)
: -qsearch<PV, false>(pos, ss+1, -beta, -alpha, DEPTH_ZERO)
{
rm.score = value;
rm.pv.resize(1);
- for (int i = 0; (ss+1)->pv && (ss+1)->pv[i] != MOVE_NONE; ++i)
- rm.pv.push_back((ss+1)->pv[i]);
+
+ assert((ss+1)->pv);
+
+ for (Move* m = (ss+1)->pv; *m != MOVE_NONE; ++m)
+ rm.pv.push_back(*m);
// We record how often the best move has been changed in each
// iteration. This information is used for time management: When
{
bestMove = SpNode ? splitPoint->bestMove = move : move;
- if (PvNode && !RootNode)
- {
- update_pv(ss->pv, move, (ss+1)->pv);
- if (SpNode)
- update_pv(splitPoint->ss->pv, move, (ss+1)->pv);
- }
+ if (PvNode && !RootNode) // Update pv even in fail-high case
+ update_pv(SpNode ? splitPoint->ss->pv : ss->pv, move, (ss+1)->pv);
if (PvNode && value < beta) // Update alpha! Always alpha < beta
alpha = SpNode ? splitPoint->alpha = value : value;
else if (bestValue >= beta && !pos.capture_or_promotion(bestMove) && !inCheck)
update_stats(pos, ss, bestMove, depth, quietsSearched, quietCount - 1);
- TT.store(posKey, value_to_tt(bestValue, ss->ply),
- bestValue >= beta ? BOUND_LOWER :
- PvNode && bestMove ? BOUND_EXACT : BOUND_UPPER,
- depth, bestMove, ss->staticEval);
+ tte->save(posKey, value_to_tt(bestValue, ss->ply),
+ bestValue >= beta ? BOUND_LOWER :
+ PvNode && bestMove ? BOUND_EXACT : BOUND_UPPER,
+ depth, bestMove, ss->staticEval, TT.get_generation());
assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
Move pv[MAX_PLY+1];
StateInfo st;
- const TTEntry* tte;
+ TTEntry* tte;
+ bool ttHit;
Key posKey;
Move ttMove, move, bestMove;
Value bestValue, value, ttValue, futilityValue, futilityBase, oldAlpha;
// Transposition table lookup
posKey = pos.key();
- tte = TT.probe(posKey);
- ttMove = tte ? tte->move() : MOVE_NONE;
- ttValue = tte ? value_from_tt(tte->value(),ss->ply) : VALUE_NONE;
+ tte = TT.probe(posKey, ttHit);
+ ttMove = ttHit ? tte->move() : MOVE_NONE;
+ ttValue = ttHit ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE;
if ( !PvNode
- && tte
+ && ttHit
&& tte->depth() >= ttDepth
&& ttValue != VALUE_NONE // Only in case of TT access race
&& (ttValue >= beta ? (tte->bound() & BOUND_LOWER)
}
else
{
- if (tte)
+ if (ttHit)
{
// Never assume anything on values stored in TT
if ((ss->staticEval = bestValue = tte->eval_value()) == VALUE_NONE)
// Stand pat. Return immediately if static value is at least beta
if (bestValue >= beta)
{
- if (!tte)
- TT.store(pos.key(), value_to_tt(bestValue, ss->ply), BOUND_LOWER,
- DEPTH_NONE, MOVE_NONE, ss->staticEval);
+ if (!ttHit)
+ tte->save(pos.key(), value_to_tt(bestValue, ss->ply), BOUND_LOWER,
+ DEPTH_NONE, MOVE_NONE, ss->staticEval, TT.get_generation());
return bestValue;
}
if (value > alpha)
{
- if (PvNode)
+ if (PvNode) // Update pv even in fail-high case
update_pv(ss->pv, move, (ss+1)->pv);
if (PvNode && value < beta) // Update alpha here! Always alpha < beta
}
else // Fail high
{
- TT.store(posKey, value_to_tt(value, ss->ply), BOUND_LOWER,
- ttDepth, move, ss->staticEval);
+ tte->save(posKey, value_to_tt(value, ss->ply), BOUND_LOWER,
+ ttDepth, move, ss->staticEval, TT.get_generation());
return value;
}
if (InCheck && bestValue == -VALUE_INFINITE)
return mated_in(ss->ply); // Plies to mate from the root
- TT.store(posKey, value_to_tt(bestValue, ss->ply),
- PvNode && bestValue > oldAlpha ? BOUND_EXACT : BOUND_UPPER,
- ttDepth, bestMove, ss->staticEval);
+ tte->save(posKey, value_to_tt(bestValue, ss->ply),
+ PvNode && bestValue > oldAlpha ? BOUND_EXACT : BOUND_UPPER,
+ ttDepth, bestMove, ss->staticEval, TT.get_generation());
assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
}
- // update_pv() copies child node pv[] adding current move
+ // update_pv() adds current move and appends child pv[]
- void update_pv(Move* pv, Move move, Move* child) {
+ void update_pv(Move* pv, Move move, Move* childPv) {
- for (*pv++ = move; child && *child != MOVE_NONE; )
- *pv++ = *child++;
+ for (*pv++ = move; childPv && *childPv != MOVE_NONE; )
+ *pv++ = *childPv++;
*pv = MOVE_NONE;
}
// Increase history value of the cut-off move and decrease all the other
// played quiet moves.
- Value bonus = Value(int(depth) * int(depth));
+ Value bonus = Value((depth / ONE_PLY) * (depth / ONE_PLY));
History.update(pos.moved_piece(move), to_sq(move), bonus);
for (int i = 0; i < quietsCnt; ++i)
{
Move Skill::pick_move() {
- static RKISS rk;
-
- // PRNG sequence should be not deterministic
- for (int i = Time::now() % 50; i > 0; --i)
- rk.rand<unsigned>();
+ // PRNG sequence should be non-deterministic, so we seed it with the time at init
+ static PRNG rng(Time::now());
// RootMoves are already sorted by score in descending order
int variance = std::min(RootMoves[0].score - RootMoves[candidates - 1].score, PawnValueMg);
int weakness = 120 - 2 * level;
- int max_s = -VALUE_INFINITE;
+ int maxScore = -VALUE_INFINITE;
best = MOVE_NONE;
// Choose best move. For each move score we add two terms both dependent on
// then we choose the move with the resulting highest score.
for (size_t i = 0; i < candidates; ++i)
{
- int s = RootMoves[i].score;
+ int score = RootMoves[i].score;
// Don't allow crazy blunders even at very low skills
- if (i > 0 && RootMoves[i - 1].score > s + 2 * PawnValueMg)
+ if (i > 0 && RootMoves[i - 1].score > score + 2 * PawnValueMg)
break;
// This is our magic formula
- s += ( weakness * int(RootMoves[0].score - s)
- + variance * (rk.rand<unsigned>() % weakness)) / 128;
+ score += ( weakness * int(RootMoves[0].score - score)
+ + variance * (rng.rand<unsigned>() % weakness)) / 128;
- if (s > max_s)
+ if (score > maxScore)
{
- max_s = s;
+ maxScore = score;
best = RootMoves[i].pv[0];
}
}
{
bool updated = (i <= PVIdx);
- if (depth == 1 && !updated)
+ if (depth == ONE_PLY && !updated)
continue;
Depth d = updated ? depth : depth - ONE_PLY;
- Value v = updated ? RootMoves[i].score : RootMoves[i].prevScore;
+ Value v = updated ? RootMoves[i].score : RootMoves[i].previousScore;
+
+ bool tb = TB::RootInTB && abs(v) < VALUE_MATE - MAX_PLY;
+ v = tb ? TB::Score : v;
if (ss.rdbuf()->in_avail()) // Not at first line
ss << "\n";
ss << "info depth " << d / ONE_PLY
<< " seldepth " << selDepth
<< " multipv " << i + 1
- << " score " << (i == PVIdx ? UCI::format_value(v, alpha, beta) : UCI::format_value(v))
+ << " score " << ((!tb && i == PVIdx) ? UCI::format_value(v, alpha, beta) : UCI::format_value(v))
<< " nodes " << pos.nodes_searched()
<< " nps " << pos.nodes_searched() * 1000 / elapsed
+ << " tbhits " << TB::Hits
<< " time " << elapsed
<< " pv";
void RootMove::insert_pv_in_tt(Position& pos) {
StateInfo state[MAX_PLY], *st = state;
- const TTEntry* tte;
size_t idx = 0;
for ( ; idx < pv.size(); ++idx)
{
- tte = TT.probe(pos.key());
+ bool ttHit;
+ TTEntry* tte = TT.probe(pos.key(), ttHit);
- if (!tte || tte->move() != pv[idx]) // Don't overwrite correct entries
- TT.store(pos.key(), VALUE_NONE, BOUND_NONE, DEPTH_NONE, pv[idx], VALUE_NONE);
+ if (!ttHit || tte->move() != pv[idx]) // Don't overwrite correct entries
+ tte->save(pos.key(), VALUE_NONE, BOUND_NONE, DEPTH_NONE, pv[idx], VALUE_NONE, TT.get_generation());
assert(MoveList<LEGAL>(pos).contains(pv[idx]));
dbg_print();
}
- if (Limits.use_time_management() && !Limits.ponder)
+ // An engine may not stop pondering until told so by the GUI
+ if (Limits.ponder)
+ return;
+
+ if (Limits.use_time_management())
{
bool stillAtFirstMove = Signals.firstRootMove
&& !Signals.failedLowAtRoot
projects / stockfish / blobdiff