Function evaluate

Rapfi/eval/eval.cpp:96–116

/// @note Board must have at least one stone placed (`ply() > 0`).
template <Rule R>
Value evaluate(const Board &board, Value alpha, Value beta)
{
    assert(board.ply() > 0);
    Color self = board.sideToMove();

    const StateInfo &st0 = board.stateInfo();
    const StateInfo &st1 = board.stateInfo(1);

    Value basicEval  = (evaluateBasic(st0, self) + evaluateBasic(st1, self)) / 2;
    Value threatEval = evaluateThreat<R>(st0, self);
    Value eval       = std::clamp(basicEval + threatEval, VALUE_EVAL_MIN, VALUE_EVAL_MAX);

    if (board.evaluator()) {
        // Use evaluator eval if classical eval are in alpha-beta window margin
        int margin = classicalEvalMargin(eval);
        if (eval >= alpha - margin && eval <= beta + margin)
            return computeEvaluatorValue(board).value();
    }

    return eval;
}

template Value evaluate<FREESTYLE>(const Board &, Value, Value);
template Value evaluate<STANDARD>(const Board &, Value, Value);