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Introduce Cut/All node definitions 

Follow Don Dailey definition of cut/all node:

"If the previous node was a cut node, we consider this an ALL node.
The only exception is for PV nodes which are a special case of ALL nodes.
In the PVS framework, the first zero width window searched from a PV
node is by our definition a CUT node and if you have to do a re-search
then it is suddenly promoted to a PV nodes (as per PVS search) and only
then can the cut and all nodes swap positions. In other words, these
internal search failures can force the status of every node in the subtree
to swap if it propagates back to the last PV nodes."

http://talkchess.com/forum/viewtopic.php?topic_view=threads&p=519741&t=47577

With this definition we have an hit rate higher than 90% on:

    if (!PvNode && depth > 4 * ONE_PLY)
        dbg_hit_on_c(cutNode, (bestValue >= beta));

And an hit rate of just 28% on:

    if (!PvNode && depth > 4 * ONE_PLY)
        dbg_hit_on_c(!cutNode, (bestValue >= beta));

No functional change.
sf_4_base
Marco Costalba 2013-06-09 09:43:04 +02:00
parent b6e9d901b0
commit 3b8f66f8ac
3 changed files with 22 additions and 20 deletions
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32
src/search.cpp
View File

@ -91,7 +91,7 @@ namespace {
CountermovesStats Countermoves;
template <NodeType NT>
Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth);
Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode);
template <NodeType NT, bool InCheck>
Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth);
@ -349,7 +349,7 @@ namespace {
// research with bigger window until not failing high/low anymore.
while (true)
{
bestValue = search<Root>(pos, ss, alpha, beta, depth * ONE_PLY);
bestValue = search<Root>(pos, ss, alpha, beta, depth * ONE_PLY, false);
// Bring to front the best move. It is critical that sorting is
// done with a stable algorithm because all the values but the first
@ -455,7 +455,7 @@ namespace {
Value rBeta = bestValue - 2 * PawnValueMg;
ss->excludedMove = RootMoves[0].pv[0];
ss->skipNullMove = true;
Value v = search<NonPV>(pos, ss, rBeta - 1, rBeta, (depth - 3) * ONE_PLY);
Value v = search<NonPV>(pos, ss, rBeta - 1, rBeta, (depth - 3) * ONE_PLY, true);
ss->skipNullMove = false;
ss->excludedMove = MOVE_NONE;
@ -485,7 +485,7 @@ namespace {
// here: This is taken care of after we return from the split point.
template <NodeType NT>
Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) {
Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode) {
const bool PvNode = (NT == PV || NT == Root || NT == SplitPointPV || NT == SplitPointRoot);
const bool SpNode = (NT == SplitPointPV || NT == SplitPointNonPV || NT == SplitPointRoot);
@ -679,7 +679,7 @@ namespace {
pos.do_null_move(st);
(ss+1)->skipNullMove = true;
nullValue = depth-R < ONE_PLY ? -qsearch<NonPV, false>(pos, ss+1, -beta, -alpha, DEPTH_ZERO)
: - search<NonPV>(pos, ss+1, -beta, -alpha, depth-R);
: - search<NonPV>(pos, ss+1, -beta, -alpha, depth-R, !cutNode);
(ss+1)->skipNullMove = false;
pos.undo_null_move();
@ -694,7 +694,7 @@ namespace {
// Do verification search at high depths
ss->skipNullMove = true;
Value v = search<NonPV>(pos, ss, alpha, beta, depth-R);
Value v = search<NonPV>(pos, ss, alpha, beta, depth-R, false);
ss->skipNullMove = false;
if (v >= beta)
@ -744,7 +744,7 @@ namespace {
{
ss->currentMove = move;
pos.do_move(move, st, ci, pos.move_gives_check(move, ci));
value = -search<NonPV>(pos, ss+1, -rbeta, -rbeta+1, rdepth);
value = -search<NonPV>(pos, ss+1, -rbeta, -rbeta+1, rdepth, !cutNode);
pos.undo_move(move);
if (value >= rbeta)
return value;
@ -759,7 +759,7 @@ namespace {
Depth d = depth - 2 * ONE_PLY - (PvNode ? DEPTH_ZERO : depth / 4);
ss->skipNullMove = true;
search<PvNode ? PV : NonPV>(pos, ss, alpha, beta, d);
search<PvNode ? PV : NonPV>(pos, ss, alpha, beta, d, true);
ss->skipNullMove = false;
tte = TT.probe(posKey);
@ -855,7 +855,7 @@ split_point_start: // At split points actual search starts from here
Value rBeta = ttValue - int(depth);
ss->excludedMove = move;
ss->skipNullMove = true;
value = search<NonPV>(pos, ss, rBeta - 1, rBeta, depth / 2);
value = search<NonPV>(pos, ss, rBeta - 1, rBeta, depth / 2, cutNode);
ss->skipNullMove = false;
ss->excludedMove = MOVE_NONE;
@ -955,7 +955,7 @@ split_point_start: // At split points actual search starts from here
if (SpNode)
alpha = splitPoint->alpha;
value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d);
value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, true);
doFullDepthSearch = (value > alpha && ss->reduction != DEPTH_ZERO);
ss->reduction = DEPTH_ZERO;
@ -972,7 +972,7 @@ split_point_start: // At split points actual search starts from here
value = newDepth < ONE_PLY ?
givesCheck ? -qsearch<NonPV, true>(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO)
: -qsearch<NonPV, false>(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO)
: - search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth);
: - search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, !cutNode);
}
// Only for PV nodes do a full PV search on the first move or after a fail
@ -982,7 +982,7 @@ split_point_start: // At split points actual search starts from here
value = newDepth < ONE_PLY ?
givesCheck ? -qsearch<PV, true>(pos, ss+1, -beta, -alpha, DEPTH_ZERO)
: -qsearch<PV, false>(pos, ss+1, -beta, -alpha, DEPTH_ZERO)
: - search<PV>(pos, ss+1, -beta, -alpha, newDepth);
: - search<PV>(pos, ss+1, -beta, -alpha, newDepth, false);
// Step 17. Undo move
pos.undo_move(move);
@ -1057,7 +1057,7 @@ split_point_start: // At split points actual search starts from here
assert(bestValue < beta);
thisThread->split<FakeSplit>(pos, ss, alpha, beta, &bestValue, &bestMove,
depth, threatMove, moveCount, &mp, NT);
depth, threatMove, moveCount, &mp, NT, cutNode);
if (bestValue >= beta)
break;
}
@ -1705,13 +1705,13 @@ void Thread::idle_loop() {
switch (sp->nodeType) {
case Root:
search<SplitPointRoot>(pos, ss, sp->alpha, sp->beta, sp->depth);
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);
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);
search<SplitPointNonPV>(pos, ss, sp->alpha, sp->beta, sp->depth, sp->cutNode);
break;
default:
assert(false);

7
src/thread.cpp
View File

@ -252,7 +252,7 @@ Thread* ThreadPool::available_slave(Thread* master) const {
template <bool Fake>
void Thread::split(Position& pos, Stack* ss, Value alpha, Value beta, Value* bestValue,
Move* bestMove, Depth depth, Move threatMove, int moveCount,
MovePicker* movePicker, int nodeType) {
MovePicker* movePicker, int nodeType, bool cutNode) {
assert(pos.pos_is_ok());
assert(*bestValue <= alpha && alpha < beta && beta <= VALUE_INFINITE);
@ -274,6 +274,7 @@ void Thread::split(Position& pos, Stack* ss, Value alpha, Value beta, Value* bes
sp.alpha = alpha;
sp.beta = beta;
sp.nodeType = nodeType;
sp.cutNode = cutNode;
sp.movePicker = movePicker;
sp.moveCount = moveCount;
sp.pos = &pos;
@ -339,8 +340,8 @@ void Thread::split(Position& pos, Stack* ss, Value alpha, Value beta, Value* bes
}
// Explicit template instantiations
template void Thread::split<false>(Position&, Stack*, Value, Value, Value*, Move*, Depth, Move, int, MovePicker*, int);
template void Thread::split< true>(Position&, Stack*, Value, Value, Value*, Move*, Depth, Move, int, MovePicker*, int);
template void Thread::split<false>(Position&, Stack*, Value, Value, Value*, Move*, Depth, Move, int, MovePicker*, int, bool);
template void Thread::split< true>(Position&, Stack*, Value, Value, Value*, Move*, Depth, Move, int, MovePicker*, int, bool);
// wait_for_think_finished() waits for main thread to go to sleep then returns

3
src/thread.h
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@ -68,6 +68,7 @@ struct SplitPoint {
Value beta;
int nodeType;
Move threatMove;
bool cutNode;
// Const pointers to shared data
MovePicker* movePicker;
@ -103,7 +104,7 @@ struct Thread {
template <bool Fake>
void split(Position& pos, Search::Stack* ss, Value alpha, Value beta, Value* bestValue, Move* bestMove,
Depth depth, Move threatMove, int moveCount, MovePicker* movePicker, int nodeType);
Depth depth, Move threatMove, int moveCount, MovePicker* movePicker, int nodeType, bool cutNode);
SplitPoint splitPoints[MAX_SPLITPOINTS_PER_THREAD];
Material::Table materialTable;