pvtable.c

#include "stdio.h"
#include "defs.h"

int GetPvLine(const int depth, S_BOARD *pos)    {   // Adding our principal variation to the PV Table array

    ASSERT(depth < MAXDEPTH);

    int move = ProbePvTable(pos);
    int count = 0;

    while (move != NOMOVE && count < depth) {

        ASSERT(count < MAXDEPTH);

        if (MoveExists(pos, move))  {
            MakeMove(pos, move);
            pos->PvArray[count++] = move;
        } else {
            break;
        }
        move = ProbePvTable(pos);
    }

    while (pos->ply > 0)    {
        TakeMove(pos);
    }

    return count;

}

const int PvSize = 0x100000 * 2;    // Size of table = 2MB

void ClearPvTable(S_PVTABLE *table) {

    S_PVENTRY *pvEntry;

    for (pvEntry = table->pTable; pvEntry < table->pTable + table->numEntries; pvEntry++)   {
        pvEntry->posKey = 0ULL;
        pvEntry->move = NOMOVE;
    }

}

void InitPvTable(S_PVTABLE *table)  {

    table->numEntries = PvSize / sizeof(S_PVENTRY);
    table->numEntries -= 2; // Indexed - want to make sure we don't fall off the end
    free(table->pTable);    // Free an element of the table
    table->pTable = (S_PVENTRY *) malloc(table->numEntries * sizeof(S_PVENTRY));    // Allocating memory as a pointer to array
    ClearPvTable(table);
    printf("PvTabel init complete with %d entries.\n", table->numEntries);
    
}

void StorePvMove(const S_BOARD *pos, const int move)    {

    int index = pos->posKey % pos->PvTable->numEntries;

    ASSERT(index >= 0 && index <= pos->PvTable->numEntries - 1);

    pos->PvTable->pTable[index].move = move;
    pos->PvTable->pTable[index].posKey = pos->posKey;

}

int ProbePvTable(const S_BOARD *pos)   {

    int index = pos->posKey % pos->PvTable->numEntries;

    ASSERT(index >= 0 && index <= pos->PvTable->numEntries - 1);

    if (pos->PvTable->pTable[index].posKey == pos->posKey)  {
        return pos->PvTable->pTable[index].move;
    }

    return NOMOVE;

}