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Retire eval margin and gains

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1/ eval margin and gains removed:
 - gains removed by Value(128): search() and qsearch() now behave consistently!

2/ futility_margin()
 - testing showed that there is no added value in this weird (log(depth), movecount)
   formula, and a much simpler linear formula is just as good. In fact, it is most
   likely better, as it is not yet optimally tuned.
 - the new simplified formula also means we get rid of FutilityMargins[], its
   initialization code, and more importantly ss->futilityMoveCount, and the hacky
   code that updates it throughout the search().
 - the current formula gives negative futility margins, and there is a hidden interaction
   between the move coutn pruning formula and the futility margin one: what happens is
   that MCP is supposed to be triggered before we use the non-sensical negative futility
   margins.

3/ unify pre & post futility pruning
 - pre futility pruning (what SF calls value based pruning) used depth < 7 plies,
   while post futility pruning (what SF calls static null move pruning) used depth < 4 plies.
 - also the condition depth < 7 in pre futility pruning was not obvious, and it seemd
   to be depth < 16 (futility_margin() returns an infinite value when depth >= 7).

Tested with fixed number of games both at short TC:
ELO: 0.82 +-2.1 (95%) LOS: 77.3%
Total: 40000 W: 7939 L: 7845 D: 24216

And long TC
ELO: 0.59 +-2.0 (95%) LOS: 71.9%
Total: 40000 W: 6876 L: 6808 D: 26316

bench: 10206576
This commit is contained in:
Lucas Braesch
2013-11-07 19:46:51 +01:00
committed by Marco Costalba
parent 52ae0efccf
commit ecd07e51d0
7 changed files with 47 additions and 112 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/evaluate.cpp
+11 -27
View File
@@ -227,7 +227,7 @@ namespace {
// Function prototypes
template<bool Trace>
Value do_evaluate(const Position& pos, Value& margin);
Value do_evaluate(const Position& pos);
template<Color Us>
void init_eval_info(const Position& pos, EvalInfo& ei);
@@ -236,7 +236,7 @@ namespace {
Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score* mobility);
template<Color Us, bool Trace>
Score evaluate_king(const Position& pos, const EvalInfo& ei, Value margins[]);
Score evaluate_king(const Position& pos, const EvalInfo& ei);
template<Color Us, bool Trace>
Score evaluate_threats(const Position& pos, const EvalInfo& ei);
@@ -262,8 +262,8 @@ namespace Eval {
/// values, an endgame score and a middle game score, and interpolates
/// between them based on the remaining material.
Value evaluate(const Position& pos, Value& margin) {
return do_evaluate<false>(pos, margin);
Value evaluate(const Position& pos) {
return do_evaluate<false>(pos);
}
@@ -305,19 +305,14 @@ namespace Eval {
namespace {
template<bool Trace>
Value do_evaluate(const Position& pos, Value& margin) {
Value do_evaluate(const Position& pos) {
assert(!pos.checkers());
EvalInfo ei;
Value margins[COLOR_NB];
Score score, mobility[2] = { SCORE_ZERO, SCORE_ZERO };
Thread* th = pos.this_thread();
// margins[] store the uncertainty estimation of position's evaluation
// that typically is used by the search for pruning decisions.
margins[WHITE] = margins[BLACK] = VALUE_ZERO;
// Initialize score by reading the incrementally updated scores included
// in the position object (material + piece square tables) and adding
// Tempo bonus. Score is computed from the point of view of white.
@@ -330,10 +325,7 @@ Value do_evaluate(const Position& pos, Value& margin) {
// If we have a specialized evaluation function for the current material
// configuration, call it and return.
if (ei.mi->specialized_eval_exists())
{
margin = VALUE_ZERO;
return ei.mi->evaluate(pos);
}
// Probe the pawn hash table
ei.pi = Pawns::probe(pos, th->pawnsTable);
@@ -351,8 +343,8 @@ Value do_evaluate(const Position& pos, Value& margin) {
// Evaluate kings after all other pieces because we need complete attack
// information when computing the king safety evaluation.
score += evaluate_king<WHITE, Trace>(pos, ei, margins)
- evaluate_king<BLACK, Trace>(pos, ei, margins);
score += evaluate_king<WHITE, Trace>(pos, ei)
- evaluate_king<BLACK, Trace>(pos, ei);
// Evaluate tactical threats, we need full attack information including king
score += evaluate_threats<WHITE, Trace>(pos, ei)
@@ -399,7 +391,6 @@ Value do_evaluate(const Position& pos, Value& margin) {
sf = ScaleFactor(50);
}
margin = margins[pos.side_to_move()];
Value v = interpolate(score, ei.mi->game_phase(), sf);
// In case of tracing add all single evaluation contributions for both white and black
@@ -412,9 +403,7 @@ Value do_evaluate(const Position& pos, Value& margin) {
Score b = ei.mi->space_weight() * evaluate_space<BLACK>(pos, ei);
Tracing::add(SPACE, apply_weight(w, Weights[Space]), apply_weight(b, Weights[Space]));
Tracing::add(TOTAL, score);
Tracing::stream << "\nUncertainty margin: White: " << to_cp(margins[WHITE])
<< ", Black: " << to_cp(margins[BLACK])
<< "\nScaling: " << std::noshowpos
Tracing::stream << "\nScaling: " << std::noshowpos
<< std::setw(6) << 100.0 * ei.mi->game_phase() / 128.0 << "% MG, "
<< std::setw(6) << 100.0 * (1.0 - ei.mi->game_phase() / 128.0) << "% * "
<< std::setw(6) << (100.0 * sf) / SCALE_FACTOR_NORMAL << "% EG.\n"
@@ -633,7 +622,7 @@ Value do_evaluate(const Position& pos, Value& margin) {
// evaluate_king() assigns bonuses and penalties to a king of a given color
template<Color Us, bool Trace>
Score evaluate_king(const Position& pos, const EvalInfo& ei, Value margins[]) {
Score evaluate_king(const Position& pos, const EvalInfo& ei) {
const Color Them = (Us == WHITE ? BLACK : WHITE);
@@ -728,12 +717,8 @@ Value do_evaluate(const Position& pos, Value& margin) {
attackUnits = std::min(99, std::max(0, attackUnits));
// Finally, extract the king danger score from the KingDanger[]
// array and subtract the score from evaluation. Set also margins[]
// value that will be used for pruning because this value can sometimes
// be very big, and so capturing a single attacking piece can therefore
// result in a score change far bigger than the value of the captured piece.
// array and subtract the score from evaluation.
score -= KingDanger[Us == Search::RootColor][attackUnits];
margins[Us] += mg_value(KingDanger[Us == Search::RootColor][attackUnits]);
}
if (Trace)
@@ -1017,8 +1002,7 @@ Value do_evaluate(const Position& pos, Value& margin) {
stream << std::showpoint << std::showpos << std::fixed << std::setprecision(2);
std::memset(scores, 0, 2 * (TOTAL + 1) * sizeof(Score));
Value margin;
do_evaluate<true>(pos, margin);
do_evaluate<true>(pos);
std::string totals = stream.str();
stream.str("");