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Improve handling of fail-highs in assumed PV

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Check all fail highs in assumed PV with greater care (fruit/Toga already does this).
Add a flag when aspiration search fails high at ply 1 to prevent search to
be terminated prematurely.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Joona Kiiski 2009-04-13 00:27:07 +03:00 • committed by Marco Costalba
parent 3e7e1a7c53
commit 22f9f0cabe
2 changed files with 31 additions and 7 deletions
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37
src/search.cpp
View file

@ -326,6 +326,7 @@ namespace {
void update_killers(Move m, SearchStack& ss);
bool fail_high_ply_1();
bool aspiration_fail_high_ply_1();
int current_search_time();
int nps();
void poll();
@ -428,6 +429,7 @@ void think(const Position &pos, bool infinite, bool ponder, int side_to_move,
{
Threads[i].nodes = 0ULL;
Threads[i].failHighPly1 = false;
Threads[i].aspirationFailHighPly1 = false;
}
NodesSincePoll = 0;
InfiniteSearch = infinite;
@ -891,7 +893,6 @@ namespace {
Value root_search(Position &pos, SearchStack ss[], RootMoveList &rml, Value alpha, Value beta) {
//FIXME: Implement bestValue
Value oldAlpha = alpha;
Value value;
Bitboard dcCandidates = pos.discovered_check_candidates(pos.side_to_move());
@ -1166,19 +1167,29 @@ namespace {
{
ss[ply].reduction = Depth(0);
value = -search(pos, ss, -alpha, newDepth, ply+1, true, threadID);
if (value > alpha && value < beta)
if (value > alpha /*&& value < beta*/)
{
// When the search fails high at ply 1 while searching the first
// move at the root, set the flag failHighPly1. This is used for
// time managment: We don't want to stop the search early in
// such cases, because resolving the fail high at ply 1 could
// result in a big drop in score at the root.
if (ply == 1 && RootMoveNumber == 1)
if (ply == 1 && RootMoveNumber == 1) {
Threads[threadID].failHighPly1 = true;
if (value >= beta) {
Threads[threadID].aspirationFailHighPly1 = true;
}
}
// A fail high occurred. Re-search at full window (pv search)
value = -search_pv(pos, ss, -beta, -alpha, newDepth, ply+1, threadID);
Threads[threadID].failHighPly1 = false;
//FIXME: Current implementation of Problem code is not completely thread-safe.
//If poll is called before pv is updated, we lose this move.
//(failHighPly1 also suffers from same kind of problems though. There is also a small
//fraction of time when failHighPly1 and Problem are _both_ false, though we
//are facing bad problems. If we are very unlucky search is terminated).
Threads[threadID].aspirationFailHighPly1 = false;
}
}
}
@ -1868,18 +1879,23 @@ namespace {
ss[sp->ply].reduction = Depth(0);
value = -search(pos, ss, -sp->alpha, newDepth, sp->ply+1, true, threadID);
if (value > sp->alpha && value < sp->beta)
if (value > sp->alpha /*&& value < sp->beta*/)
{
// When the search fails high at ply 1 while searching the first
// move at the root, set the flag failHighPly1. This is used for
// time managment: We don't want to stop the search early in
// such cases, because resolving the fail high at ply 1 could
// result in a big drop in score at the root.
if (sp->ply == 1 && RootMoveNumber == 1)
if (sp->ply == 1 && RootMoveNumber == 1) {
Threads[threadID].failHighPly1 = true;
if (value >= sp->beta) {
Threads[threadID].aspirationFailHighPly1 = true;
}
}
value = -search_pv(pos, ss, -sp->beta, -sp->alpha, newDepth, sp->ply+1, threadID);
Threads[threadID].failHighPly1 = false;
Threads[threadID].aspirationFailHighPly1 = false;
}
}
pos.undo_move(move);
@ -2466,6 +2482,13 @@ namespace {
return false;
}
bool aspiration_fail_high_ply_1() {
for(int i = 0; i < ActiveThreads; i++)
if(Threads[i].aspirationFailHighPly1)
return true;
return false;
}
// current_search_time() returns the number of milliseconds which have passed
// since the beginning of the current search.
@ -2544,8 +2567,8 @@ namespace {
return;
bool overTime = t > AbsoluteMaxSearchTime
|| (RootMoveNumber == 1 && t > MaxSearchTime + ExtraSearchTime && !FailLow) //FIXME: BUG??
|| ( !FailHigh && !FailLow && !fail_high_ply_1() && !Problem
|| (RootMoveNumber == 1 && t > MaxSearchTime + ExtraSearchTime && !FailLow && !aspiration_fail_high_ply_1())
|| ( !FailHigh && !FailLow && !fail_high_ply_1() && !aspiration_fail_high_ply_1() && !Problem
&& t > 6*(MaxSearchTime + ExtraSearchTime));
if ( (Iteration >= 3 && (!InfiniteSearch && overTime))

1
src/thread.h
View file

@ -67,6 +67,7 @@ struct Thread {
int activeSplitPoints;
uint64_t nodes;
bool failHighPly1;
bool aspirationFailHighPly1;
volatile bool stop;
volatile bool running;
volatile bool idle;