From: Marco Costalba Date: Thu, 16 Apr 2009 06:35:26 +0000 (+0200) Subject: Merge Joona's new aspiration window search X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=4634be8ba6176e71579fa01f5fd2c74e41eedad6;hp=e7f03913eaa10454850f79f2e54826af7d9ebb70 Merge Joona's new aspiration window search It seems very positive. After 999 games at 1'+0" result is: +249 -216 =534 +11 ELO And after another 456 games we still have: +122 -113 =221 --- diff --git a/src/search.cpp b/src/search.cpp index 1582b7bc..21aa4f92 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -47,6 +47,26 @@ namespace { /// Types + // IterationInfoType stores search results for each iteration + // + // Because we use relatively small (dynamic) aspiration window, + // there happens many fail highs and fail lows in root. And + // because we don't do researches in those cases, "value" stored + // here is not necessarily exact. Instead in case of fail high/low + // we guess what the right value might be and store our guess + // as a "speculated value" and then move on. Speculated values are + // used just to calculate aspiration window width, so also if are + // not exact is not big a problem. + + struct IterationInfoType { + + IterationInfoType(Value v = Value(0), Value sv = Value(0)) + : value(v), speculatedValue(sv) {} + + Value value, speculatedValue; + }; + + // The BetaCounterType class is used to order moves at ply one. // Apart for the first one that has its score, following moves // normally have score -VALUE_INFINITE, so are ordered according @@ -196,7 +216,7 @@ namespace { BetaCounterType BetaCounter; // Scores and number of times the best move changed for each iteration: - Value ValueByIteration[PLY_MAX_PLUS_2]; + IterationInfoType IterationInfo[PLY_MAX_PLUS_2]; int BestMoveChangesByIteration[PLY_MAX_PLUS_2]; // MultiPV mode @@ -214,6 +234,7 @@ namespace { bool AbortSearch; bool Quit; bool FailHigh; + bool FailLow; bool Problem; bool PonderingEnabled; int ExactMaxTime; @@ -246,13 +267,10 @@ namespace { /// Functions Value id_loop(const Position &pos, Move searchMoves[]); - Value root_search(Position &pos, SearchStack ss[], RootMoveList &rml); - 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, bool allowNullmove, int threadID); - Value qsearch(Position &pos, SearchStack ss[], Value alpha, Value beta, - Depth depth, int ply, int threadID); + Value root_search(Position &pos, SearchStack ss[], RootMoveList &rml, Value alpha, Value beta); + 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, bool allowNullmove, 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_pv(SplitPoint *sp, int threadID); void init_node(SearchStack ss[], int ply, int threadID); @@ -380,6 +398,7 @@ void think(const Position &pos, bool infinite, bool ponder, int side_to_move, AbortSearch = false; Quit = false; FailHigh = false; + FailLow = false; Problem = false; ExactMaxTime = maxTime; @@ -654,14 +673,13 @@ namespace { ss[i].init(i); ss[i].initKillers(); } - ValueByIteration[0] = Value(0); - ValueByIteration[1] = rml.get_move_score(0); + IterationInfo[1] = IterationInfoType(rml.get_move_score(0), rml.get_move_score(0)); Iteration = 1; EasyMove = rml.scan_for_easy_move(); // Iterative deepening loop - while (!AbortSearch && Iteration < PLY_MAX) + while (Iteration < PLY_MAX) { // Initialize iteration rml.sort(); @@ -672,8 +690,62 @@ namespace { std::cout << "info depth " << Iteration << std::endl; + // Calculate dynamic search window based on previous iterations + Value alpha, beta; + + if (MultiPV == 1 && Iteration >= 6) + { + int prevDelta1 = IterationInfo[Iteration - 1].speculatedValue - IterationInfo[Iteration - 2].speculatedValue; + int prevDelta2 = IterationInfo[Iteration - 2].speculatedValue - IterationInfo[Iteration - 3].speculatedValue; + + int delta = Max(2 * abs(prevDelta1) + abs(prevDelta2), ProblemMargin); + + alpha = Max(IterationInfo[Iteration - 1].value - delta, -VALUE_INFINITE); + beta = Min(IterationInfo[Iteration - 1].value + delta, VALUE_INFINITE); + } + else + { + alpha = - VALUE_INFINITE; + beta = VALUE_INFINITE; + } + // Search to the current depth - ValueByIteration[Iteration] = root_search(p, ss, rml); + Value value = root_search(p, ss, rml, alpha, beta); + + // Write PV to transposition table, in case the relevant entries have + // been overwritten during the search. + TT.insert_pv(p, ss[0].pv); + + if (AbortSearch) + break; // Value cannot be trusted. Break out immediately! + + //Save info about search result + Value speculatedValue; + bool fHigh = false; + bool fLow = false; + Value delta = value - IterationInfo[Iteration - 1].value; + + if (value >= beta) + { + assert(delta > 0); + + fHigh = true; + speculatedValue = value + delta; + BestMoveChangesByIteration[Iteration] += 2; // Allocate more time + } + else if (value <= alpha) + { + assert(value == alpha); + assert(delta < 0); + + fLow = true; + speculatedValue = value + delta; + BestMoveChangesByIteration[Iteration] += 3; // Allocate more time + } else + speculatedValue = value; + + speculatedValue = Min(Max(speculatedValue, -VALUE_INFINITE), VALUE_INFINITE); + IterationInfo[Iteration] = IterationInfoType(value, speculatedValue); // Erase the easy move if it differs from the new best move if (ss[0].pv[0] != EasyMove) @@ -692,13 +764,15 @@ namespace { // Stop search early when the last two iterations returned a mate score if ( Iteration >= 6 - && abs(ValueByIteration[Iteration]) >= abs(VALUE_MATE) - 100 - && abs(ValueByIteration[Iteration-1]) >= abs(VALUE_MATE) - 100) + && abs(IterationInfo[Iteration].value) >= abs(VALUE_MATE) - 100 + && abs(IterationInfo[Iteration-1].value) >= abs(VALUE_MATE) - 100) stopSearch = true; // Stop search early if one move seems to be much better than the rest int64_t nodes = nodes_searched(); if ( Iteration >= 8 + && !fLow + && !fHigh && EasyMove == ss[0].pv[0] && ( ( rml.get_move_cumulative_nodes(0) > (nodes * 85) / 100 && current_search_time() > MaxSearchTime / 16) @@ -719,15 +793,13 @@ namespace { if (stopSearch) { + //FIXME: Implement fail-low emergency measures if (!PonderSearch) break; else StopOnPonderhit = true; } } - // Write PV to transposition table, in case the relevant entries have - // been overwritten during the search: - TT.insert_pv(p, ss[0].pv); if (MaxDepth && Iteration >= MaxDepth) break; @@ -784,15 +856,23 @@ namespace { // scheme (perhaps we should try to use this at internal PV nodes, too?) // and prints some information to the standard output. - Value root_search(Position &pos, SearchStack ss[], RootMoveList &rml) { + Value root_search(Position &pos, SearchStack ss[], RootMoveList &rml, Value alpha, Value beta) { - Value alpha = -VALUE_INFINITE; - Value beta = VALUE_INFINITE, value; + Value oldAlpha = alpha; + Value value; Bitboard dcCandidates = pos.discovered_check_candidates(pos.side_to_move()); // Loop through all the moves in the root move list for (int i = 0; i < rml.move_count() && !AbortSearch; i++) { + if (alpha >= beta) + { + // We failed high, invalidate and skip next moves, leave node-counters + // and beta-counters as they are and quickly return, we will try to do + // a research at the next iteration with a bigger aspiration window. + rml.set_move_score(i, -VALUE_INFINITE); + continue; + } int64_t nodes; Move move; StateInfo st; @@ -825,12 +905,12 @@ namespace { if (i < MultiPV) { - value = -search_pv(pos, ss, -beta, VALUE_INFINITE, newDepth, 1, 0); + value = -search_pv(pos, ss, -beta, -alpha, newDepth, 1, 0); // If the value has dropped a lot compared to the last iteration, // set the boolean variable Problem to true. This variable is used // for time managment: When Problem is true, we try to complete the // current iteration before playing a move. - Problem = (Iteration >= 2 && value <= ValueByIteration[Iteration-1] - ProblemMargin); + Problem = (Iteration >= 2 && value <= IterationInfo[Iteration-1].value - ProblemMargin); if (Problem && StopOnPonderhit) StopOnPonderhit = false; @@ -855,7 +935,7 @@ namespace { // was aborted because the user interrupted the search or because we // ran out of time. In this case, the return value of the search cannot // be trusted, and we break out of the loop without updating the best - // move and/or PV: + // move and/or PV. if (AbortSearch) break; @@ -874,7 +954,7 @@ namespace { rml.set_move_score(i, -VALUE_INFINITE); else { - // New best move! + // PV move or new best move! // Update PV rml.set_move_score(i, value); @@ -906,11 +986,12 @@ namespace { LogFile << pretty_pv(pos, current_search_time(), Iteration, nodes_searched(), value, ss[0].pv) << std::endl; - alpha = value; + if (value > alpha) + alpha = value; // Reset the global variable Problem to false if the value isn't too // far below the final value from the last iteration. - if (value > ValueByIteration[Iteration - 1] - NoProblemMargin) + if (value > IterationInfo[Iteration - 1].value - NoProblemMargin) Problem = false; } else // MultiPV > 1 @@ -934,7 +1015,11 @@ namespace { } alpha = rml.get_move_score(Min(i, MultiPV-1)); } - } + } // New best move case + + assert(alpha >= oldAlpha); + + FailLow = (alpha == oldAlpha); } return alpha; } @@ -1083,7 +1168,7 @@ namespace { // (from the computer's point of view) since the previous iteration: if ( ply == 1 && Iteration >= 2 - && -value <= ValueByIteration[Iteration-1] - ProblemMargin) + && -value <= IterationInfo[Iteration-1].value - ProblemMargin) Problem = true; } @@ -1796,7 +1881,7 @@ namespace { // (from the computer's point of view) since the previous iteration. if ( sp->ply == 1 && Iteration >= 2 - && -value <= ValueByIteration[Iteration-1] - ProblemMargin) + && -value <= IterationInfo[Iteration-1].value - ProblemMargin) Problem = true; } lock_release(&(sp->lock)); @@ -2425,8 +2510,8 @@ namespace { return; bool overTime = t > AbsoluteMaxSearchTime - || (RootMoveNumber == 1 && t > MaxSearchTime + ExtraSearchTime) - || ( !FailHigh && !fail_high_ply_1() && !Problem + || (RootMoveNumber == 1 && t > MaxSearchTime + ExtraSearchTime && !FailLow) //FIXME: We are not checking any problem flags, BUG? + || ( !FailHigh && !FailLow && !fail_high_ply_1() && !Problem && t > 6*(MaxSearchTime + ExtraSearchTime)); if ( (Iteration >= 3 && (!InfiniteSearch && overTime)) @@ -2447,8 +2532,8 @@ namespace { (!InfiniteSearch && (StopOnPonderhit || t > AbsoluteMaxSearchTime || (RootMoveNumber == 1 && - t > MaxSearchTime + ExtraSearchTime) || - (!FailHigh && !fail_high_ply_1() && !Problem && + t > MaxSearchTime + ExtraSearchTime && !FailLow) || + (!FailHigh && !FailLow && !fail_high_ply_1() && !Problem && t > 6*(MaxSearchTime + ExtraSearchTime))))) AbortSearch = true; }