Trader Bot: Implement Kelly Criterion for optimal position sizing

csharp/TraderBot/KellyCriterion.cs

@@ -0,0 +1,79 @@
+namespace TraderBot;
+
+public static class KellyCriterion
+{
+    /// <summary>
+    /// Calculates the optimal bet size fraction using the Kelly Criterion formula.
+    /// Formula: f = (bp - q) / b
+    /// Where:
+    /// - f = fraction of capital to bet
+    /// - b = profit/loss ratio (odds)
+    /// - p = probability of winning
+    /// - q = probability of losing (1-p)
+    /// </summary>
+    /// <param name="winProbability">Probability of winning (0.0 to 1.0)</param>
+    /// <param name="profitLossRatio">The ratio of profit to loss (e.g., 2.0 means profit is 2x the loss)</param>
+    /// <param name="maxFraction">Maximum fraction to limit risk (default 0.25)</param>
+    /// <returns>The optimal fraction of capital to bet (0.0 to maxFraction)</returns>
+    public static double CalculateOptimalBetSize(double winProbability, double profitLossRatio, double maxFraction = 0.25)
+    {
+        if (winProbability < 0 || winProbability > 1)
+            throw new ArgumentException("Win probability must be between 0 and 1", nameof(winProbability));
+
+        if (profitLossRatio <= 0)
+            throw new ArgumentException("Profit/loss ratio must be positive", nameof(profitLossRatio));
+
+        if (maxFraction <= 0 || maxFraction > 1)
+            throw new ArgumentException("Max fraction must be between 0 and 1", nameof(maxFraction));
+
+        double lossProbability = 1.0 - winProbability;
+
+        // Kelly Criterion formula: f = (bp - q) / b
+        double kellyFraction = (profitLossRatio * winProbability - lossProbability) / profitLossRatio;
+
+        // Return 0 if Kelly suggests negative betting (negative expected value)
+        if (kellyFraction <= 0)
+            return 0.0;
+
+        // Cap at maximum fraction to limit risk
+        return Math.Min(kellyFraction, maxFraction);
+    }
+
+    /// <summary>
+    /// Calculates the win probability and profit/loss ratio from historical operations
+    /// </summary>
+    /// <param name="operations">List of completed operations</param>
+    /// <returns>Tuple containing (winProbability, profitLossRatio)</returns>
+    public static (double WinProbability, double ProfitLossRatio) CalculateHistoricalMetrics(
+        IEnumerable<(DateTime Date, decimal BuyPrice, decimal SellPrice)> operations)
+    {
+        var operationsList = operations.ToList();
+        if (operationsList.Count < 10) // Need minimum historical data
+            return (0.5, 1.0); // Default conservative values
+
+        var wins = 0;
+        var totalProfit = 0.0m;
+        var totalLoss = 0.0m;
+
+        foreach (var op in operationsList)
+        {
+            var profit = op.SellPrice - op.BuyPrice;
+            if (profit > 0)
+            {
+                wins++;
+                totalProfit += profit;
+            }
+            else if (profit < 0)
+            {
+                totalLoss += Math.Abs(profit);
+            }
+        }
+
+        var winProbability = (double)wins / operationsList.Count;
+        var avgProfit = wins > 0 ? (double)(totalProfit / wins) : 0.0;
+        var avgLoss = (operationsList.Count - wins) > 0 ? (double)(totalLoss / (operationsList.Count - wins)) : 1.0;
+        var profitLossRatio = avgLoss > 0 ? avgProfit / avgLoss : 1.0;
+
+        return (winProbability, Math.Max(profitLossRatio, 0.1)); // Minimum ratio to avoid division issues
+    }
+}

csharp/TraderBot/TradingService.cs

@@ -39,6 +39,7 @@ public class TradingService : BackgroundService
     protected readonly ConcurrentDictionary<string, OrderState> ActiveSellOrders;
     protected readonly ConcurrentDictionary<decimal, long> LotsSets;
     protected readonly ConcurrentDictionary<string, decimal> ActiveSellOrderSourcePrice;
+    protected readonly List<(DateTime Date, decimal BuyPrice, decimal SellPrice)> CompletedOperations;
 
     public TradingService(ILogger<TradingService> logger, InvestApiClient investApi, IHostApplicationLifetime lifetime, TradingSettings settings)
     {
@@ -111,6 +112,7 @@ public TradingService(ILogger<TradingService> logger, InvestApiClient investApi,
         ActiveSellOrders = new ConcurrentDictionary<string, OrderState>();
         LotsSets = new ConcurrentDictionary<decimal, long>();
         ActiveSellOrderSourcePrice = new ConcurrentDictionary<string, decimal>();
+        CompletedOperations = new List<(DateTime, decimal, decimal)>();
         LastOperationsCheckpoint = settings.LoadOperationsFrom;
     }
 
@@ -290,7 +292,15 @@ protected void TrySubtractTradesFromOrder(ConcurrentDictionary<string, OrderStat
             if (activeOrder.LotsRequested == 0)
             {
                 orders.TryRemove(orderTrades.OrderId, out activeOrder);
-                ActiveSellOrderSourcePrice.TryRemove(orderTrades.OrderId, out decimal sourcePrice);
+
+                // Track completed buy-sell cycle for Kelly Criterion
+                if (orders == ActiveSellOrders && ActiveSellOrderSourcePrice.TryGetValue(orderTrades.OrderId, out decimal sourcePrice))
+                {
+                    var sellPrice = MoneyValueToDecimal(activeOrder.InitialSecurityPrice);
+                    TrackCompletedOperation(sourcePrice, sellPrice);
+                }
+
+                ActiveSellOrderSourcePrice.TryRemove(orderTrades.OrderId, out decimal _);
                 Logger.LogInformation($"Active order removed: {activeOrder}");
             }
         }
@@ -477,7 +487,7 @@ await marketDataStream.RequestStream.WriteAsync(new MarketDataRequest
                             {
                                 Logger.LogInformation($"buy activated");
                                 Logger.LogInformation($"bid: {bestBid}, ask: {bestAsk}.");
-                                var lots = (long)(cashBalance / lotPrice);
+                                var lots = CalculateOptimalLotSize(cashBalance, lotPrice);
                                 var marketLotsAtTargetPrice = orderBook.Bids.FirstOrDefault(o => o.Price == bestBid)?.Quantity ?? 0;
                                 Logger.LogInformation($"marketLotsAtTargetPrice: {marketLotsAtTargetPrice}");
                                 var response = await PlaceBuyOrder(lots, bestBid);
@@ -544,7 +554,7 @@ await marketDataStream.RequestStream.WriteAsync(new MarketDataRequest
                                 var lotPrice = bestBid * LotSize;
                                 if (cashBalance > lotPrice)
                                 {
-                                    var lots = (long)(cashBalance / lotPrice);
+                                    var lots = CalculateOptimalLotSize(cashBalance, lotPrice);
                                     var marketLotsAtTargetPrice = orderBook.Bids.FirstOrDefault(o => o.Price == bestBid)?.Quantity ?? 0;
                                     Logger.LogInformation($"marketLotsAtTargetPrice: {marketLotsAtTargetPrice}");
                                     var response = await PlaceBuyOrder(lots, bestBid);
@@ -652,6 +662,57 @@ private bool IsTimeToBuy()
     {
        var currentTime = DateTime.UtcNow.TimeOfDay;
        return currentTime > MinimumTimeToBuy && currentTime < MaximumTimeToBuy;
+    }
+
+    private long CalculateOptimalLotSize(decimal cashBalance, decimal lotPrice)
+    {
+        if (!Settings.UseKellyCriterion)
+        {
+            // Use traditional sizing: all available cash
+            return (long)(cashBalance / lotPrice);
+        }
+
+        double winProbability = Settings.WinProbability;
+        double profitLossRatio = Settings.ProfitLossRatio;
+
+        // If we have enough historical data, calculate metrics dynamically
+        if (CompletedOperations.Count >= 10)
+        {
+            var (historicalWinProb, historicalRatio) = KellyCriterion.CalculateHistoricalMetrics(CompletedOperations);
+            winProbability = historicalWinProb;
+            profitLossRatio = historicalRatio;
+            Logger.LogInformation($"Using historical metrics - Win Probability: {winProbability:F3}, Profit/Loss Ratio: {profitLossRatio:F3}");
+        }
+        else
+        {
+            Logger.LogInformation($"Using configured metrics - Win Probability: {winProbability:F3}, Profit/Loss Ratio: {profitLossRatio:F3}");
+        }
+
+        var kellyFraction = KellyCriterion.CalculateOptimalBetSize(winProbability, profitLossRatio, Settings.KellyFractionLimit);
+        var optimalCashToUse = cashBalance * (decimal)kellyFraction;
+        var lots = (long)Math.Max(1, optimalCashToUse / lotPrice); // Ensure at least 1 lot
+
+        Logger.LogInformation($"Kelly Criterion: Fraction={kellyFraction:F3}, OptimalCash={optimalCashToUse:F2}, Lots={lots}");
+
+        return lots;
+    }
+
+    private void TrackCompletedOperation(decimal buyPrice, decimal sellPrice)
+    {
+        lock (CompletedOperations)
+        {
+            CompletedOperations.Add((DateTime.UtcNow, buyPrice, sellPrice));
+
+            // Keep only last 100 operations to prevent memory growth
+            if (CompletedOperations.Count > 100)
+            {
+                CompletedOperations.RemoveAt(0);
+            }
+        }
+
+        var profit = sellPrice - buyPrice;
+        var profitPercent = (profit / buyPrice) * 100;
+        Logger.LogInformation($"Operation completed: Buy={buyPrice}, Sell={sellPrice}, Profit={profit:F4} ({profitPercent:F2}%)");
     } 
 
     private async Task<(decimal, decimal)> GetCashBalance(bool forceRemote = false)

csharp/TraderBot/TradingSettings.cs

@@ -17,4 +17,8 @@ public class TradingSettings
     public long EarlySellOwnedLotsDelta { get; set; }
     public decimal EarlySellOwnedLotsMultiplier { get; set; }
     public DateTime LoadOperationsFrom { get; set; }
+    public bool UseKellyCriterion { get; set; }
+    public double WinProbability { get; set; }
+    public double ProfitLossRatio { get; set; }
+    public double KellyFractionLimit { get; set; } = 0.25;
 }

csharp/TraderBot/appsettings.TMON.json

@@ -24,6 +24,10 @@
     "MaximumTimeToBuy": "23:59:59",
     "EarlySellOwnedLotsDelta": 300000,
     "EarlySellOwnedLotsMultiplier": 0,
-    "LoadOperationsFrom": "2025-03-01T00:00:01.3389860Z"
+    "LoadOperationsFrom": "2025-03-01T00:00:01.3389860Z",
+    "UseKellyCriterion": true,
+    "WinProbability": 0.55,
+    "ProfitLossRatio": 1.2,
+    "KellyFractionLimit": 0.25
   }
 }

csharp/TraderBot/appsettings.TRUR.json

@@ -24,6 +24,10 @@
     "MaximumTimeToBuy": "14:45:00",
     "EarlySellOwnedLotsDelta": 300000,
     "EarlySellOwnedLotsMultiplier": 0,
-    "LoadOperationsFrom": "2025-03-01T00:00:01.3389860Z"
+    "LoadOperationsFrom": "2025-03-01T00:00:01.3389860Z",
+    "UseKellyCriterion": true,
+    "WinProbability": 0.52,
+    "ProfitLossRatio": 1.1,
+    "KellyFractionLimit": 0.2
   }
 }