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Document Pawnidx[] and Pfactor[]

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This commit is contained in:
Marco Costalba 2016-05-16 08:50:51 +02:00
parent 306561431b
commit 1cbaaaef68
1 changed files with 28 additions and 14 deletions
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42
src/syzygy/tbprobe.cpp
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@ -218,9 +218,9 @@ std::string TBPaths;
std::deque<WDLEntry> WDLTable;
std::list<DTZEntry> DTZTable;
int Binomial[6][64];
int Pawnidx[5][24];
int Pfactor[5][4];
int Binomial[6][64]; // [k][n] k elements from a set of n elements
int LeadPawnIdx[4][24]; // [leadPawnsCnt - 1][MapToEdges[Sq]]
int LeadPawnsGroupSize[4][4]; // [leadPawnsCnt - 1][FILE_A..FILE_D]
enum { BigEndian, LittleEndian };
@ -767,7 +767,7 @@ uint64_t probe_table(const Position& pos, Entry* entry, WDLScore wdl = WDLDraw,
// Encode leading pawns. Note that any previous horizontal flip preserves
// the order because MapToEdges[] is (almost) flip invariant.
if (entry->hasPawns) {
idx = Pawnidx[leadPawnsCnt - 1][23 - MapToEdges[squares[0]] / 2];
idx = LeadPawnIdx[leadPawnsCnt - 1][23 - MapToEdges[squares[0]] / 2];
for (int i = 1; i < leadPawnsCnt; ++i)
idx += Binomial[i][MapToEdges[squares[leadPawnsCnt- i]]];
@ -928,7 +928,7 @@ uint64_t set_groups(T& e, PairsData* d, int order[], File f)
{
d->groupSize[0] = size;
size *= e.hasPawns ? Pfactor[d->groupLen[0] - 1][f]
size *= e.hasPawns ? LeadPawnsGroupSize[d->groupLen[0] - 1][f]
: e.hasUniquePieces ? 31332 : 462;
}
else if (k == order[1]) // Remaining pawns
@ -1594,18 +1594,32 @@ void Tablebases::init(const std::string& paths)
Binomial[k][n] = (k > 0 ? Binomial[k - 1][n - 1] : 0)
+ (k < n ? Binomial[k ][n - 1] : 0);
for (int k = 0; k < 5; ++k) {
int n = 0;
// Init tables for the encoding of leading pawns group: with 6-men TB we
// can have up to 4 leading pawns (KPPPPK).
for (int leadPawnsCnt = 1; leadPawnsCnt <= 4; ++leadPawnsCnt)
{
int mappedLeadSq = 0; // From a2 to d7 (a2a7...d2d7) mapped to 0..23
for (int f = 1; f <= 4; ++f) {
int s = 0;
for (File f = FILE_A; f <= FILE_D; ++f)
{
// Restart the index at every file because TB table is splitted
// by file, so we can reuse the same index for different files.
int idx = 0;
for ( ; n < 6 * f; ++n) {
Pawnidx[k][n] = s;
s += Binomial[k][47 - 2 * n];
// Sum all possible combinations for a given file, starting with
// the leading pawn on rank 2 and increasing the rank.
for (Rank r = RANK_2; r <= RANK_7; ++r, ++mappedLeadSq)
{
LeadPawnIdx[leadPawnsCnt - 1][mappedLeadSq] = idx;
// Given the leadSq any other pawn cannot be below or more
// toward the edge of leadSq. Start with 47 available squares
// when lead pawn is in a2 and after an increase the number is
// reduced by two due to mirroring, e.g. a3 -> no a2, h2
idx += Binomial[leadPawnsCnt - 1][47 - 2 * mappedLeadSq];
}
Pfactor[k][f - 1] = s;
// After a file is traversed, store the cumulated per-file index
LeadPawnsGroupSize[leadPawnsCnt - 1][f] = idx;
}
}