Шахматные программы. Общие вопросы

622 	// Dive into quiescence search when the depth reaches zero

623 	if (depth < = 0)

624 	     return qsearch< PvNode ? PV : NonPV>(pos, ss, alpha, beta);

1581 	    else

1582 	    {

1583 	        unadjustedStaticEval = evaluate(pos);

1584 	        ss->staticEval       = bestValue =

1585 	          to_corrected_static_eval(unadjustedStaticEval, correctionValue);

1586 	    }



1588 	    // Stand pat. Return immediately if static value is at least beta

1589 	    if (bestValue >= beta)

1590 	    {

1591 	        if (!is_decisive(bestValue))

1592 	            bestValue = (bestValue + beta) / 2;

...	        ...

1598 	        return bestValue;

1599 	    }



1601 	    if (bestValue > alpha)

1602 	        alpha = bestValue;

734 	else

735 	{

736 	    unadjustedStaticEval = evaluate(pos);

737 	    ss->staticEval = eval = to_corrected_static_eval(unadjustedStaticEval, correctionValue);



739 	    // Static evaluation is saved as it was before adjustment by correction history

740 	    ttWriter.write(posKey, VALUE_NONE, ss->ttPv, BOUND_NONE, DEPTH_UNSEARCHED, Move::none(),

741 	                   unadjustedStaticEval, tt.generation());

742 	}

if (...)

    {

	value = -search(...);

    }

870 	// Step 7. Razoring

873 	if (!PvNode && eval < alpha - 485 - 281 * depth * depth)

874 	    return qsearch< NonPV>(pos, ss, alpha, beta);



876 	// Step 8. Futility pruning: child node

878 	{

879 	    auto futility_margin = [&](Depth d) {

...	    ...

885 	    };



887 	    if (!ss->ttPv && depth < 14 && eval - futility_margin(depth) >= beta && eval >= beta

888 	        && (!ttData.move || ttCapture) && !is_loss(beta) && !is_win(eval))

889 	        return (2 * beta + eval) / 3;

890 	}

892 	// Step 9. Null move search with verification search

893 	if (cutNode && ss->staticEval >= beta - 18 * depth + 350 && !excludedMove

894 	    && pos.non_pawn_material(us) && ss->ply >= nmpMinPly && !is_loss(beta))

895 	{

...	...

898 	    // Null move dynamic reduction based on depth

899 	    Depth R = 7 + depth / 3;

900 	    do_null_move(pos, st, ss);

902 	    Value nullValue = -search< NonPV>(pos, ss + 1, -beta, -beta + 1, depth - R, false);

904 	    undo_null_move(pos);



906 	    // Do not return unproven mate or TB scores

907 	    if (nullValue >= beta && !is_win(nullValue))

908 	    {

...	    ...

914 	        // Do verification search at high depths, with null move pruning disabled

915 	        // until ply exceeds nmpMinPly.

916 	        nmpMinPly = ss->ply + 3 * (depth - R) / 4;

918 	        Value v = search< NonPV>(pos, ss, beta - 1, beta, depth - R, false);

920 	        nmpMinPly = 0;



922 	        if (v >= beta)

923 	            return nullValue;

924 	    }

925 	}

929 	// Step 10. Internal iterative reductions

932 	if (!allNode && depth >= 6 && !ttData.move && priorReduction < = 3)

933 	    depth--;

935 	// Step 11. ProbCut

936 	// If we have a good enough capture (or queen promotion) and a reduced search

937 	// returns a value much above beta, we can (almost) safely prune the previous move.

938 	probCutBeta = beta + 235 - 63 * improving;

939 	if (depth >= 3

940 	    && !is_decisive(beta)

941 	    // If value from transposition table is lower than probCutBeta, don't attempt probCut there

943 	    && !(is_valid(ttData.value) && ttData.value < probCutBeta))

944 	{

...	...

947 	    MovePicker mp(pos, ttData.move, probCutBeta - ss->staticEval, &captureHistory);

948 	    Depth      probCutDepth = std::clamp(depth - 5 - (ss->staticEval - beta) / 315, 0, depth);



950 	    while ((move = mp.next_move()) != Move::none())

951 	    {

...	        ...

959 	        do_move(pos, move, st, ss);



961 	        // Perform a preliminary qsearch to verify that the move holds

962 	        value = -qsearch< NonPV>(pos, ss + 1, -probCutBeta, -probCutBeta + 1);



964 	        // If the qsearch held, perform the regular search

965 	        if (value >= probCutBeta && probCutDepth > 0)

966 	            value = -search< NonPV>(pos, ss + 1, -probCutBeta, -probCutBeta + 1, probCutDepth,

967 	                                   !cutNode);



969 	        undo_move(pos, move);



971 	        if (value >= probCutBeta)

972 	        {

973 	            // Save ProbCut data into transposition table

974 	            ttWriter.write(posKey, value_to_tt(value, ss->ply), ss->ttPv, BOUND_LOWER,

975 	                           probCutDepth + 1, move, unadjustedStaticEval, tt.generation());



977 	            if (!is_decisive(value))

978 	                return value - (probCutBeta - beta);

979 	        }

980 	    }

981 	}