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Symmetric King Safety: take 2

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Another attempt at retiring current asymmetric
king evaluation and use a much simpler symmetric
one. As a good side effect we can avoid recalculating
eval after a null move.

Tested in no-regression mode and passed

STC
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 21580 W: 3752 L: 3632 D: 14196

LTC
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 18253 W: 2593 L: 2469 D: 13191

And a LTC regression test against SF DD to
verify we don't have regression against
weaker engines due to some kind of 'contempt'
effect:

ELO: 54.69 +-2.1 (95%) LOS: 100.0%
Total: 40000 W: 11072 L: 4827 D: 24101

bench: 8205159
This commit is contained in:
Lucas Braesch
2014-06-03 20:48:43 +08:00
committed by Marco Costalba
parent 187a9fe5e7
commit adeded29fb
4 changed files with 36 additions and 47 deletions
Download Patch File Download Diff File Expand all files Collapse all files

33
src/search.cpp
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@@ -42,7 +42,6 @@ namespace Search {
LimitsType Limits;
std::vector<RootMove> RootMoves;
Position RootPos;
Color RootColor;
Time::point SearchTime;
StateStackPtr SetupStates;
}
@@ -77,6 +76,9 @@ namespace {
return (Depth) Reductions[PvNode][i][std::min(int(d) / ONE_PLY, 63)][std::min(mn, 63)];
}
// Tempo bonus. Must be handled by search to preserve eval symmetry.
const int Tempo = 17;
size_t MultiPV, PVIdx;
TimeManager TimeMgr;
double BestMoveChanges;
@@ -180,12 +182,11 @@ uint64_t Search::perft(Position& pos, Depth depth) {
void Search::think() {
RootColor = RootPos.side_to_move();
TimeMgr.init(Limits, RootPos.game_ply(), RootColor);
TimeMgr.init(Limits, RootPos.game_ply(), RootPos.side_to_move());
int cf = Options["Contempt Factor"] * PawnValueEg / 100; // From centipawns
DrawValue[ RootColor] = VALUE_DRAW - Value(cf);
DrawValue[~RootColor] = VALUE_DRAW + Value(cf);
DrawValue[ RootPos.side_to_move()] = VALUE_DRAW - Value(cf);
DrawValue[~RootPos.side_to_move()] = VALUE_DRAW + Value(cf);
if (RootMoves.empty())
{
@@ -203,8 +204,8 @@ void Search::think() {
log << "\nSearching: " << RootPos.fen()
<< "\ninfinite: " << Limits.infinite
<< " ponder: " << Limits.ponder
<< " time: " << Limits.time[RootColor]
<< " increment: " << Limits.inc[RootColor]
<< " time: " << Limits.time[RootPos.side_to_move()]
<< " increment: " << Limits.inc[RootPos.side_to_move()]
<< " moves to go: " << Limits.movestogo
<< "\n" << std::endl;
}
@@ -472,7 +473,7 @@ namespace {
bestValue = -VALUE_INFINITE;
ss->currentMove = ss->ttMove = (ss+1)->excludedMove = bestMove = MOVE_NONE;
ss->ply = (ss-1)->ply + 1;
(ss+1)->skipNullMove = false; (ss+1)->reduction = DEPTH_ZERO;
(ss+1)->skipNullMove = (ss+1)->nullChild = false; (ss+1)->reduction = DEPTH_ZERO;
(ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE;
// Used to send selDepth info to GUI
@@ -483,7 +484,7 @@ namespace {
{
// Step 2. Check for aborted search and immediate draw
if (Signals.stop || pos.is_draw() || ss->ply > MAX_PLY)
return ss->ply > MAX_PLY && !inCheck ? evaluate(pos) : DrawValue[pos.side_to_move()];
return ss->ply > MAX_PLY && !inCheck ? evaluate(pos) + Tempo : DrawValue[pos.side_to_move()];
// Step 3. Mate distance pruning. Even if we mate at the next move our score
// would be at best mate_in(ss->ply+1), but if alpha is already bigger because
@@ -538,7 +539,7 @@ namespace {
{
// Never assume anything on values stored in TT
if ((ss->staticEval = eval = tte->eval_value()) == VALUE_NONE)
eval = ss->staticEval = evaluate(pos);
eval = ss->staticEval = evaluate(pos) + Tempo;
// Can ttValue be used as a better position evaluation?
if (ttValue != VALUE_NONE)
@@ -547,7 +548,7 @@ namespace {
}
else
{
eval = ss->staticEval = evaluate(pos);
eval = ss->staticEval = ss->nullChild ? -(ss-1)->staticEval + 2 * Tempo : evaluate(pos) + Tempo;
TT.store(posKey, VALUE_NONE, BOUND_NONE, DEPTH_NONE, MOVE_NONE, ss->staticEval);
}
@@ -607,10 +608,10 @@ namespace {
+ int(eval - beta) / PawnValueMg * ONE_PLY;
pos.do_null_move(st);
(ss+1)->skipNullMove = true;
(ss+1)->skipNullMove = (ss+1)->nullChild = 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)->skipNullMove = (ss+1)->nullChild = false;
pos.undo_null_move();
if (nullValue >= beta)
@@ -1065,7 +1066,7 @@ moves_loop: // When in check and at SpNode search starts from here
// Check for an instant draw or if the maximum ply has been reached
if (pos.is_draw() || ss->ply > MAX_PLY)
return ss->ply > MAX_PLY && !InCheck ? evaluate(pos) : DrawValue[pos.side_to_move()];
return ss->ply > MAX_PLY && !InCheck ? evaluate(pos) + Tempo : DrawValue[pos.side_to_move()];
// Decide whether or not to include checks: this fixes also the type of
// TT entry depth that we are going to use. Note that in qsearch we use
@@ -1102,7 +1103,7 @@ moves_loop: // When in check and at SpNode search starts from here
{
// Never assume anything on values stored in TT
if ((ss->staticEval = bestValue = tte->eval_value()) == VALUE_NONE)
ss->staticEval = bestValue = evaluate(pos);
ss->staticEval = bestValue = evaluate(pos) + Tempo;
// Can ttValue be used as a better position evaluation?
if (ttValue != VALUE_NONE)
@@ -1110,7 +1111,7 @@ moves_loop: // When in check and at SpNode search starts from here
bestValue = ttValue;
}
else
ss->staticEval = bestValue = evaluate(pos);
ss->staticEval = bestValue = ss->nullChild ? -(ss-1)->staticEval + 2 * Tempo : evaluate(pos) + Tempo;
// Stand pat. Return immediately if static value is at least beta
if (bestValue >= beta)