SgProbCut.cpp

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//----------------------------------------------------------------------------
/** @file SgProbCut.cpp
    See SgProbCut.h. */
//----------------------------------------------------------------------------

#include "SgSystem.h"
#include "SgProbCut.h"

#include "SgMath.h"
#include "SgSearch.h"

//----------------------------------------------------------------------------

bool SgProbCut::ProbCut(SgSearch& search, int depth, int alpha, int beta,
                       SgSearchStack& moveStack, bool* isExactValue,
                       int* value)
{
    SG_ASSERT(IsEnabled());
    SetEnabled(false);

    Cutoff c;
    int index = 0;
    while (GetCutoff(depth / SgSearch::DEPTH_UNIT, index++, c))
    {
        SgSearchStack newStack;
        bool isExact;
        float threshold = GetThreshold();

        if (beta < SgSearch::SG_INFINITY-1)
        {
            float b = (+threshold * c.sigma + float(beta) - c.b) / c.a;
            int bound = SgMath::RoundToInt(b);
            int res = search.SearchEngine(c.shallow * SgSearch::DEPTH_UNIT,
                                   bound-1, bound, newStack, &isExact);
            if (res >= bound)
            {
                SetEnabled(true);
                newStack.PushAll(moveStack);
                newStack.SwapWith(moveStack);
                *isExactValue = isExact;
                *value = beta;
                return true;
            }
        }

        if (alpha > -SgSearch::SG_INFINITY + 1)
        {
            float b = (-threshold * c.sigma + float(alpha) - c.b) / c.a;
            int bound = SgMath::RoundToInt(b);
            int res = search.SearchEngine(c.shallow * SgSearch::DEPTH_UNIT,
                                   bound, bound+1, newStack, &isExact);

            if (res <= bound)
            {
                SetEnabled(true);
                newStack.PushAll(moveStack);
                newStack.SwapWith(moveStack);
                *isExactValue = isExact;
                *value = alpha;
                return true;
            }
        }
    }
    SetEnabled(true);
    return false;
}

//----------------------------------------------------------------------------