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Additional work in bitbases

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Verified the generated bitbases are unchanged.

No functional change.
This commit is contained in:
Marco Costalba 2015-01-24 08:51:53 +01:00
parent 18375e3bfb
commit 69407ae9b8
1 changed files with 39 additions and 34 deletions
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73
src/bitbase.cpp
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@ -57,7 +57,7 @@ namespace {
struct KPKPosition {
KPKPosition() = default;
KPKPosition(unsigned idx);
explicit KPKPosition(unsigned idx);
operator Result() const { return result; }
Result classify(const std::vector<KPKPosition>& db)
{ return us == WHITE ? classify<WHITE>(db) : classify<BLACK>(db); }
@ -66,7 +66,7 @@ namespace {
unsigned id;
Color us;
Square bksq, wksq, psq;
Square ksq[COLOR_NB], psq;
Result result;
};
@ -92,7 +92,7 @@ void Bitbases::init() {
// Iterate through the positions until none of the unknown positions can be
// changed to either wins or draws (15 cycles needed).
while (std::accumulate(db.begin(), db.end(), false, [&](bool repeat, KPKPosition& pos)
{ return (pos == UNKNOWN && pos.classify(db) != UNKNOWN) || repeat; }));
{ return (pos == UNKNOWN && pos.classify(db) != UNKNOWN) || repeat; })){}
// Map 32 results into one KPKBitbase[] entry
for (auto& pos : db)
@ -105,44 +105,47 @@ namespace {
KPKPosition::KPKPosition(unsigned idx) {
id = idx;
wksq = Square((idx >> 0) & 0x3F);
bksq = Square((idx >> 6) & 0x3F);
us = Color ((idx >> 12) & 0x01);
psq = make_square(File((idx >> 13) & 0x3), RANK_7 - Rank((idx >> 15) & 0x7));
result = UNKNOWN;
id = idx;
ksq[WHITE] = Square((idx >> 0) & 0x3F);
ksq[BLACK] = Square((idx >> 6) & 0x3F);
us = Color ((idx >> 12) & 0x01);
psq = make_square(File((idx >> 13) & 0x3), RANK_7 - Rank((idx >> 15) & 0x7));
// Check if two pieces are on the same square or if a king can be captured
if ( distance(wksq, bksq) <= 1
|| wksq == psq
|| bksq == psq
|| (us == WHITE && (StepAttacksBB[PAWN][psq] & bksq)))
if ( distance(ksq[WHITE], ksq[BLACK]) <= 1
|| ksq[WHITE] == psq
|| ksq[BLACK] == psq
|| (us == WHITE && (StepAttacksBB[PAWN][psq] & ksq[BLACK])))
result = INVALID;
else if (us == WHITE)
{
// Immediate win if a pawn can be promoted without getting captured
if ( rank_of(psq) == RANK_7
&& wksq != psq + DELTA_N
&& ( distance(bksq, psq + DELTA_N) > 1
||(StepAttacksBB[KING][wksq] & (psq + DELTA_N))))
result = WIN;
}
// Immediate win if a pawn can be promoted without getting captured
else if ( us == WHITE
&& rank_of(psq) == RANK_7
&& ksq[us] != psq + DELTA_N
&& ( distance(ksq[~us], psq + DELTA_N) > 1
|| (StepAttacksBB[KING][ksq[us]] & (psq + DELTA_N))))
result = WIN;
// Immediate draw if it is a stalemate or a king captures undefended pawn
else if ( !(StepAttacksBB[KING][bksq] & ~(StepAttacksBB[KING][wksq] | StepAttacksBB[PAWN][psq]))
|| (StepAttacksBB[KING][bksq] & psq & ~StepAttacksBB[KING][wksq]))
else if ( us == BLACK
&& ( !(StepAttacksBB[KING][ksq[us]] & ~(StepAttacksBB[KING][ksq[~us]] | StepAttacksBB[PAWN][psq]))
|| (StepAttacksBB[KING][ksq[us]] & psq & ~StepAttacksBB[KING][ksq[~us]])))
result = DRAW;
// Position will be classified later
else
result = UNKNOWN;
}
template<Color Us>
Result KPKPosition::classify(const std::vector<KPKPosition>& db) {
// White to Move: If one move leads to a position classified as WIN, the result
// White to move: If one move leads to a position classified as WIN, the result
// of the current position is WIN. If all moves lead to positions classified
// as DRAW, the current position is classified as DRAW, otherwise the current
// position is classified as UNKNOWN.
//
// Black to Move: If one move leads to a position classified as DRAW, the result
// Black to move: If one move leads to a position classified as DRAW, the result
// of the current position is DRAW. If all moves lead to positions classified
// as WIN, the position is classified as WIN, otherwise the current position is
// classified as UNKNOWN.
@ -152,19 +155,21 @@ namespace {
const Result Bad = (Us == WHITE ? DRAW : WIN);
Result r = INVALID;
Bitboard b = StepAttacksBB[KING][Us == WHITE ? wksq : bksq];
Bitboard b = StepAttacksBB[KING][ksq[Us]];
while (b)
r |= Us == WHITE ? db[index(Them, bksq, pop_lsb(&b), psq)]
: db[index(Them, pop_lsb(&b), wksq, psq)];
r |= Us == WHITE ? db[index(Them, ksq[Them] , pop_lsb(&b), psq)]
: db[index(Them, pop_lsb(&b), ksq[Them] , psq)];
if (Us == WHITE && rank_of(psq) < RANK_7)
if (Us == WHITE)
{
Square s = psq + DELTA_N;
r |= db[index(BLACK, bksq, wksq, s)]; // Single push
if (rank_of(psq) < RANK_7) // Single push
r |= db[index(Them, ksq[Them], ksq[Us], psq + DELTA_N)];
if (rank_of(psq) == RANK_2 && s != wksq && s != bksq)
r |= db[index(BLACK, bksq, wksq, s + DELTA_N)]; // Double push
if ( rank_of(psq) == RANK_2 // Double push
&& psq + DELTA_N != ksq[Us]
&& psq + DELTA_N != ksq[Them])
r |= db[index(Them, ksq[Them], ksq[Us], psq + DELTA_N + DELTA_N)];
}
return result = r & Good ? Good : r & UNKNOWN ? UNKNOWN : Bad;