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Use exceptions to stop the search

Browse source 
Instead of classical flags, throw an
exception when we want to immediately halt
the search. Currently only one type
is used for both UCI stop and threads
cut off.

No functional change.
This commit is contained in:
Marco Costalba 2013-08-14 08:29:57 +02:00
parent bd8f463b7e
commit 11b1a76f35
2 changed files with 30 additions and 24 deletions
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2
src/Makefile
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@ -232,7 +232,7 @@ ifeq ($(COMP),clang)
endif
### 3.2 General compiler settings
CXXFLAGS = -Wall -Wcast-qual -fno-exceptions -fno-rtti $(EXTRACXXFLAGS)
CXXFLAGS = -Wall -Wcast-qual -fno-rtti $(EXTRACXXFLAGS)
ifeq ($(comp),gcc)
CXXFLAGS += -ansi -pedantic -Wno-long-long -Wextra -Wshadow

52
src/search.cpp
View file

@ -21,6 +21,7 @@
#include <cassert>
#include <cmath>
#include <cstring>
#include <exception>
#include <iostream>
#include <sstream>
@ -104,6 +105,8 @@ namespace {
bool refutes(const Position& pos, Move first, Move second);
string uci_pv(const Position& pos, int depth, Value alpha, Value beta);
class stop : public std::exception {};
struct Skill {
Skill(int l) : level(l), best(MOVE_NONE) {}
~Skill() {
@ -356,7 +359,9 @@ namespace {
// research with bigger window until not failing high/low anymore.
while (true)
{
bestValue = search<Root>(pos, ss, alpha, beta, depth * ONE_PLY, false);
try {
bestValue = search<Root>(pos, ss, alpha, beta, depth * ONE_PLY, false);
} catch (stop&) {}
// Bring to front the best move. It is critical that sorting is
// done with a stable algorithm because all the values but the first
@ -541,10 +546,13 @@ namespace {
if (PvNode && thisThread->maxPly < ss->ply)
thisThread->maxPly = ss->ply;
if (Signals.stop || thisThread->cutoff_occurred())
throw stop();
if (!RootNode)
{
// Step 2. Check for aborted search and immediate draw
if (Signals.stop || pos.is_draw() || ss->ply > MAX_PLY)
if (pos.is_draw() || ss->ply > MAX_PLY)
return DrawValue[pos.side_to_move()];
// Step 3. Mate distance pruning. Even if we mate at the next move our score
@ -999,13 +1007,6 @@ moves_loop: // When in check and at SpNode search starts from here
alpha = splitPoint->alpha;
}
// Finished searching the move. If Signals.stop is true, the search
// 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 don't update the best move and/or PV.
if (Signals.stop || thisThread->cutoff_occurred())
return value; // To avoid returning VALUE_INFINITE
if (RootNode)
{
RootMove& rm = *std::find(RootMoves.begin(), RootMoves.end(), move);
@ -1696,21 +1697,26 @@ void Thread::idle_loop() {
activePosition = &pos;
switch (sp->nodeType) {
case Root:
search<SplitPointRoot>(pos, ss, sp->alpha, sp->beta, sp->depth, sp->cutNode);
break;
case PV:
search<SplitPointPV>(pos, ss, sp->alpha, sp->beta, sp->depth, sp->cutNode);
break;
case NonPV:
search<SplitPointNonPV>(pos, ss, sp->alpha, sp->beta, sp->depth, sp->cutNode);
break;
default:
assert(false);
}
try {
switch (sp->nodeType) {
case Root:
search<SplitPointRoot>(pos, ss, sp->alpha, sp->beta, sp->depth, sp->cutNode);
break;
case PV:
search<SplitPointPV>(pos, ss, sp->alpha, sp->beta, sp->depth, sp->cutNode);
break;
case NonPV:
search<SplitPointNonPV>(pos, ss, sp->alpha, sp->beta, sp->depth, sp->cutNode);
break;
default:
assert(false);
}
assert(searching);
assert(searching);
}
catch (stop&) {
sp->mutex.lock(); // Exception is thrown out of lock
}
searching = false;
activePosition = NULL;