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Fix Contempt Factor implementation

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First disable Contempt Factor during analysis, then
calculate the modified draw score from the point of
view of the player, so from the point of view of
RootPosition color.

Thanks to Ryan Taker for suggesting the fixes.

No functional change.
This commit is contained in:
Marco Costalba 2012-10-06 10:12:34 +02:00
parent ff9ca3e76e
commit cedbd3332a
3 changed files with 12 additions and 5 deletions
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8
src/evaluate.cpp
View file

@ -268,7 +268,8 @@ namespace {
namespace Eval {
Color RootColor;
Value ValueDrawContempt;
Value ContemptFactor;
Value ValueDraw[2];
/// evaluate() is the main evaluation function. It always computes two
/// values, an endgame score and a middle game score, and interpolates
@ -309,7 +310,10 @@ namespace Eval {
KingDangerTable[0][i] = apply_weight(make_score(t, 0), Weights[KingDangerThem]);
}
ValueDrawContempt = VALUE_DRAW - Options["Contempt Factor"] * PawnValueMg / 100;
if (Options["UCI_AnalyseMode"])
ContemptFactor = VALUE_ZERO;
else
ContemptFactor = Options["Contempt Factor"] * PawnValueMg / 100;
}

3
src/evaluate.h
View file

@ -27,7 +27,8 @@ class Position;
namespace Eval {
extern Color RootColor;
extern Value ValueDrawContempt;
extern Value ContemptFactor;
extern Value ValueDraw[2];
extern void init();
extern Value evaluate(const Position& pos, Value& margin);

6
src/search.cpp
View file

@ -199,6 +199,8 @@ void Search::think() {
Position& pos = RootPosition;
Chess960 = pos.is_chess960();
Eval::RootColor = pos.side_to_move();
Eval::ValueDraw[ Eval::RootColor] = VALUE_DRAW - Eval::ContemptFactor;
Eval::ValueDraw[~Eval::RootColor] = VALUE_DRAW + Eval::ContemptFactor;
TimeMgr.init(Limits, pos.startpos_ply_counter(), pos.side_to_move());
TT.new_search();
H.clear();
@ -538,7 +540,7 @@ namespace {
{
// Step 2. Check for aborted search and immediate draw
if (Signals.stop || pos.is_draw<false>() || ss->ply > MAX_PLY)
return Eval::ValueDrawContempt;
return Eval::ValueDraw[pos.side_to_move()];
// Step 3. Mate distance pruning. Even if we mate at the next move our score
// would be at best mate_in(ss->ply+1), but if alpha is already bigger because
@ -1094,7 +1096,7 @@ split_point_start: // At split points actual search starts from here
// Check for an instant draw or maximum ply reached
if (pos.is_draw<true>() || ss->ply > MAX_PLY)
return Eval::ValueDrawContempt;
return Eval::ValueDraw[pos.side_to_move()];
// Decide whether or not to include checks, this fixes also the type of
// TT entry depth that we are going to use. Note that in qsearch we use