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Code Issues Releases Wiki Activity

Simplify verification search (#1362)

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1. avoid recursive call of verification.
   For the interested side to move recursion makes no sense.
   For the other side it could make sense in case of mutual zugzwang,
   but I was not able to figure out any concrete problematic position.
   Allows the removal of 2 local variables.
   
2. avoid further reduction by removing R += ONE_PLY;

Benchmark with zugzwang-suite (see #1338), max 45 secs per position:
Patch  solves 33 out of 37
Master solves 31 out of 37

STC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 76188 W: 13866 L: 13840 D: 48482
http://tests.stockfishchess.org/tests/view/5a5612ed0ebc590297da516c

LTC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 40479 W: 5247 L: 5152 D: 30080
http://tests.stockfishchess.org/tests/view/5a56f7d30ebc590299e4550e

bench: 5340015
This commit is contained in:
Günther Demetz 2018-01-13 09:01:23 +01:00 • committed by Marco Costalba
parent aa88261a8f
commit 1b6459195c
3 changed files with 7 additions and 12 deletions
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13
src/search.cpp
View file

@ -676,7 +676,7 @@ namespace {
if ( !PvNode if ( !PvNode
&& eval >= beta && eval >= beta
&& ss->staticEval >= beta - 36 * depth / ONE_PLY + 225 && ss->staticEval >= beta - 36 * depth / ONE_PLY + 225
&& (ss->ply >= thisThread->nmp_ply || ss->ply % 2 == thisThread->pair)) && (ss->ply >= thisThread->nmp_ply || ss->ply % 2 != thisThread->nmp_odd))
{ {
assert(eval - beta >= 0); assert(eval - beta >= 0);
@ -698,21 +698,18 @@ namespace {
if (nullValue >= VALUE_MATE_IN_MAX_PLY) if (nullValue >= VALUE_MATE_IN_MAX_PLY)
nullValue = beta; nullValue = beta;
if (depth < 12 * ONE_PLY && abs(beta) < VALUE_KNOWN_WIN) if (abs(beta) < VALUE_KNOWN_WIN && (depth < 12 * ONE_PLY || thisThread->nmp_ply))
return nullValue; return nullValue;
// Do verification search at high depths // Do verification search at high depths
R += ONE_PLY;
// disable null move pruning for side to move for the first part of the remaining search tree // disable null move pruning for side to move for the first part of the remaining search tree
int nmp_ply = thisThread->nmp_ply;
int pair = thisThread->pair;
thisThread->nmp_ply = ss->ply + 3 * (depth-R) / 4; thisThread->nmp_ply = ss->ply + 3 * (depth-R) / 4;
thisThread->pair = (ss->ply % 2) == 0; thisThread->nmp_odd = ss->ply % 2;
Value v = depth-R < ONE_PLY ? qsearch<NonPV, false>(pos, ss, beta-1, beta) Value v = depth-R < ONE_PLY ? qsearch<NonPV, false>(pos, ss, beta-1, beta)
: search<NonPV>(pos, ss, beta-1, beta, depth-R, false, true); : search<NonPV>(pos, ss, beta-1, beta, depth-R, false, true);
thisThread->pair = pair;
thisThread->nmp_ply = nmp_ply; thisThread->nmp_odd = thisThread->nmp_ply = 0;
if (v >= beta) if (v >= beta)
return nullValue; return nullValue;

4
src/thread.cpp
View file

@ -187,12 +187,10 @@ void ThreadPool::start_thinking(Position& pos, StateListPtr& states,
for (Thread* th : *this) for (Thread* th : *this)
{ {
th->nodes = th->tbHits = 0; th->nodes = th->tbHits = th->nmp_ply = th->nmp_odd = 0;
th->rootDepth = th->completedDepth = DEPTH_ZERO; th->rootDepth = th->completedDepth = DEPTH_ZERO;
th->rootMoves = rootMoves; th->rootMoves = rootMoves;
th->rootPos.set(pos.fen(), pos.is_chess960(), &setupStates->back(), th); th->rootPos.set(pos.fen(), pos.is_chess960(), &setupStates->back(), th);
th->nmp_ply = 0;
th->pair = -1;
} }
setupStates->back() = tmp; setupStates->back() = tmp;

2
src/thread.h
View file

@ -61,7 +61,7 @@ public:
Material::Table materialTable; Material::Table materialTable;
Endgames endgames; Endgames endgames;
size_t PVIdx; size_t PVIdx;
int selDepth, nmp_ply, pair; int selDepth, nmp_ply, nmp_odd;
std::atomic<uint64_t> nodes, tbHits; std::atomic<uint64_t> nodes, tbHits;
Position rootPos; Position rootPos;