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Make using quiescence search implicit

Browse source 
If search depth is less than ONE_PLY call qsearch(), no need to check the
depth condition at various call sites of search().

Passed STC:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 14568 W: 3011 L: 2877 D: 8680
http://tests.stockfishchess.org/tests/view/5aa846190ebc59029781015b

Also helps gcc to find some optimizations (smaller binary, some speedup).
Thanks to Aram and Stefan for identifying an oversight in an early version.

Closes https://github.com/official-stockfish/Stockfish/pull/1487

No functional change.
This commit is contained in:
Joost VandeVondele 2018-03-15 09:21:34 +01:00 • committed by Stéphane Nicolet
parent 8db75dd9ec
commit 8ab12c9012
1 changed files with 11 additions and 8 deletions
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19
src/search.cpp
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@ -491,6 +491,10 @@ namespace {
template <NodeType NT>
Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode, bool skipEarlyPruning) {
// Use quiescence search when needed
if (depth < ONE_PLY)
return qsearch<NT>(pos, ss, alpha, beta);
const bool PvNode = NT == PV;
const bool rootNode = PvNode && ss->ply == 0;
@ -695,6 +699,7 @@ namespace {
else if (eval + RazorMargin2 <= alpha)
{
Value ralpha = alpha - RazorMargin2;
Value v = qsearch<NonPV>(pos, ss, ralpha, ralpha+1);
if (v <= ralpha)
@ -724,8 +729,9 @@ namespace {
ss->contHistory = thisThread->contHistory[NO_PIECE][0].get();
pos.do_null_move(st);
Value nullValue = depth-R < ONE_PLY ? -qsearch<NonPV>(pos, ss+1, -beta, -beta+1)
: - 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, true);
pos.undo_null_move();
if (nullValue >= beta)
@ -742,8 +748,7 @@ namespace {
thisThread->nmp_ply = ss->ply + 3 * (depth-R) / 4;
thisThread->nmp_odd = ss->ply % 2;
Value v = depth-R < ONE_PLY ? qsearch<NonPV>(pos, ss, beta-1, beta)
: search<NonPV>(pos, ss, beta-1, beta, depth-R, false, true);
Value v = search<NonPV>(pos, ss, beta-1, beta, depth-R, false, true);
thisThread->nmp_odd = thisThread->nmp_ply = 0;
@ -1009,8 +1014,7 @@ moves_loop: // When in check, search starts from here
// Step 17. Full depth search when LMR is skipped or fails high
if (doFullDepthSearch)
value = newDepth < ONE_PLY ? -qsearch<NonPV>(pos, ss+1, -(alpha+1), -alpha)
: - search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, !cutNode, false);
value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, !cutNode, false);
// 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
@ -1020,8 +1024,7 @@ moves_loop: // When in check, search starts from here
(ss+1)->pv = pv;
(ss+1)->pv[0] = MOVE_NONE;
value = newDepth < ONE_PLY ? -qsearch<PV>(pos, ss+1, -beta, -alpha)
: - search<PV>(pos, ss+1, -beta, -alpha, newDepth, false, false);
value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, false, false);
}
// Step 18. Undo move