Subversion Repositories Games.Chess Giants

#ifndef RTB_PROBE_HPP_

#define RTB_PROBE_HPP_

#include <string>

class Position;

namespace Syzygy {

extern int TBLargest;

void init(const std::string& path);

// Probe the WDL table for a particular position.

// If *success != 0, the probe was successful.

// The return value is from the point of view of the side to move:

// -2 : loss

// -1 : loss, but draw under 50-move rule

//  0 : draw

//  1 : win, but draw under 50-move rule

//  2 : win

int probe_wdl(Position& pos, int *success);

// Probe the DTZ table for a particular position.

// If *success != 0, the probe was successful.

// The return value is from the point of view of the side to move:

//         n < -100 : loss, but draw under 50-move rule

// -100 <= n < -1   : loss in n ply (assuming 50-move counter == 0)

//         0        : draw

//     1 < n <= 100 : win in n ply (assuming 50-move counter == 0)

//   100 < n        : win, but draw under 50-move rule

//

// The return value n can be off by 1: a return value -n can mean a loss

// in n+1 ply and a return value +n can mean a win in n+1 ply. This

// cannot happen for tables with positions exactly on the "edge" of

// the 50-move rule.

//

// This implies that if dtz > 0 is returned, the position is certainly

// a win if dtz + 50-move-counter <= 99. Care must be taken that the engine

// picks moves that preserve dtz + 50-move-counter <= 99.

//

// If n = 100 immediately after a capture or pawn move, then the position

// is also certainly a win, and during the whole phase until the next

// capture or pawn move, the inequality to be preserved is

// dtz + 50-movecounter <= 100.

//

// In short, if a move is available resulting in dtz + 50-move-counter <= 99,

// then do not accept moves leading to dtz + 50-move-counter == 100.

//

int probe_dtz(Position& pos, int *success);

}

#endif