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🔍 RFP: add history factor - simple impl with quiet history #1329

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🔍 RFP: add history factor - simple impl with quiet history #1329

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3 changes: 3 additions & 0 deletions src/Lynx/Configuration.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -186,6 +186,9 @@ public int Threads
[SPSA<int>(1, 300, 15)]
public int RFP_DepthScalingFactor { get; set; } = 52;

[SPSA<int>(200, 600, 20)]
public int RFP_HistoryDivisor { get; set; } = 400;

[SPSA<int>(1, 10, 0.5)]
public int Razoring_MaxDepth { get; set; } = 2;

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4 changes: 3 additions & 1 deletion src/Lynx/Search/NegaMax.cs
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Expand Up @@ -148,8 +148,10 @@ private int NegaMax(int depth, int ply, int alpha, int beta, bool cutnode, Cance
var improvingFactor = improvingRate * (0.75 * depth);

var rfpThreshold = rfpMargin + improvingFactor;
var previousMove = Game.ReadMoveFromStack(ply - 1);
var previousMoveHistory = _quietHistory[previousMove.Piece()][previousMove.TargetSquare()];

if (staticEval - rfpThreshold >= beta)
if (staticEval - rfpThreshold >= beta + previousMoveHistory / Configuration.EngineSettings.RFP_HistoryDivisor)
{
#pragma warning disable S3949 // Calculations should not overflow - value is being set at the beginning of the else if (!pvNode)
return (staticEval + beta) / 2;
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