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Extend full 3 fold detection to PvNodes

And restore old behaviour of not returning from a RootNode
without updating RootMoves[].

Also renamed is_draw() template parameters to reflect a
'positive' logic (Check instead of Skip) that is easier
to follow.

New bench: 5312693
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1 parent 71f37ac commit c594b989c0a7ff37002a4720e5bb667da70bb476 @mcostalba committed Oct 26, 2012
Showing with 14 additions and 26 deletions.
  1. +10 −18 src/position.cpp
  2. +1 −1 src/position.h
  3. +3 −7 src/search.cpp
View
@@ -1467,48 +1467,40 @@ Value Position::compute_non_pawn_material(Color c) const {
/// Position::is_draw() tests whether the position is drawn by material,
/// repetition, or the 50 moves rule. It does not detect stalemates, this
/// must be done by the search.
-template<bool SkipRepetition, bool SkipThreeFoldCheck>
+template<bool CheckRepetition, bool CheckThreeFold>
bool Position::is_draw() const {
- // Draw by material?
if ( !pieces(PAWN)
&& (non_pawn_material(WHITE) + non_pawn_material(BLACK) <= BishopValueMg))
return true;
- // Draw by the 50 moves rule?
if (st->rule50 > 99 && (!in_check() || MoveList<LEGAL>(*this).size()))
return true;
- // Draw by repetition?
- if (!SkipRepetition)
+ if (CheckRepetition)
{
- int i = 4, e = std::min(st->rule50, st->pliesFromNull), rep_count=0;
+ int i = 4, e = std::min(st->rule50, st->pliesFromNull);
if (i <= e)
{
StateInfo* stp = st->previous->previous;
- do {
+ for (int cnt = 0; i <= e; i += 2)
+ {
stp = stp->previous->previous;
- if (stp->key == st->key)
- {
- if(SkipThreeFoldCheck) return true;
- else if(++rep_count>=2) return true;
- }
-
- i +=2;
-
- } while (i <= e);
+ if (stp->key == st->key && (!CheckThreeFold || ++cnt >= 2))
+ return true;
+ }
}
}
return false;
}
// Explicit template instantiations
-template bool Position::is_draw<false,true>() const;
-template bool Position::is_draw<true,true>() const;
+template bool Position::is_draw<true, true>() const;
+template bool Position::is_draw<true, false>() const;
template bool Position::is_draw<false,false>() const;
View
@@ -183,7 +183,7 @@ class Position {
Thread* this_thread() const;
int64_t nodes_searched() const;
void set_nodes_searched(int64_t n);
- template<bool SkipRepetition, bool SkipThreeFoldCheck> bool is_draw() const;
+ template<bool CheckRepetition, bool CheckThreeFold> bool is_draw() const;
// Position consistency check, for debugging
bool pos_is_ok(int* failedStep = NULL) const;
View
@@ -524,7 +524,7 @@ namespace {
if (!RootNode)
{
// Step 2. Check for aborted search and immediate draw
- if (Signals.stop || pos.is_draw<false,true>() || ss->ply > MAX_PLY)
+ if (Signals.stop || pos.is_draw<true, PvNode>() || 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
@@ -538,10 +538,6 @@ namespace {
if (alpha >= beta)
return alpha;
}
- else
- {
- if(pos.is_draw<false,false>()) return DrawValue[pos.side_to_move()];
- }
// Step 4. Transposition table lookup
// We don't want the score of a partial search to overwrite a previous full search
@@ -1107,7 +1103,7 @@ namespace {
ss->ply = (ss-1)->ply + 1;
// Check for an instant draw or maximum ply reached
- if (pos.is_draw<true,true>() || ss->ply > MAX_PLY)
+ if (pos.is_draw<false, false>() || ss->ply > MAX_PLY)
return DrawValue[pos.side_to_move()];
// Transposition table lookup. At PV nodes, we don't use the TT for
@@ -1556,7 +1552,7 @@ void RootMove::extract_pv_from_tt(Position& pos) {
&& pos.is_pseudo_legal(m)
&& pos.pl_move_is_legal(m, pos.pinned_pieces())
&& ply < MAX_PLY
- && (!pos.is_draw<false,true>() || ply < 2))
+ && (!pos.is_draw<true, true>() || ply < 2))
{
pv.push_back(m);
pos.do_move(m, *st++);

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