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FX Carry Trade Strategy

This currency strategy ranks a universe of currency instruments by the interest rate differential between the base and quote currencies. At the start of each month it goes long the TopK highest‑carry symbols and shorts the TopK lowest. Profits aim to capture positive carry on longs while paying the negative carry on shorts.

Interest rate differentials are gathered from each security’s yield data. Positions are sized equally and rebalanced monthly; any instrument leaving the top or bottom groups is closed and replaced.

Details

  • Entry Criteria:
    • On the first trading day of the month, compute the interest rate differential for each currency.
    • Go long the TopK currencies with the highest carry and short the TopK with the lowest carry if order values exceed MinTradeUsd.
  • Long/Short: Long top carry, short bottom carry.
  • Exit Criteria: Positions are closed when a currency leaves the selected sets at the next rebalance.
  • Stops: None.
  • Default Values:
    • Universe – list of currency securities.
    • TopK = 3.
    • CandleType = 1 day.
    • MinTradeUsd – minimum trade value.
  • Filters:
    • Category: Carry.
    • Direction: Long & short.
    • Timeframe: Monthly.
    • Rebalance: Monthly.
using System;
using System.Collections.Generic;

using Ecng.Common;

using StockSharp.Algo.Indicators;
using StockSharp.Algo.Strategies;
using StockSharp.BusinessEntities;
using StockSharp.Configuration;
using StockSharp.Messages;

namespace StockSharp.Samples.Strategies;

/// <summary>
/// FX carry trade strategy that trades the primary instrument when its synthetic carry exceeds or lags a benchmark currency.
/// </summary>
public class FXCarryTradeStrategy : Strategy
{
	private readonly StrategyParam<string> _security2Id;
	private readonly StrategyParam<int> _carryLength;
	private readonly StrategyParam<int> _lookbackPeriod;
	private readonly StrategyParam<decimal> _entryThreshold;
	private readonly StrategyParam<decimal> _exitThreshold;
	private readonly StrategyParam<int> _cooldownBars;
	private readonly StrategyParam<decimal> _stopLoss;
	private readonly StrategyParam<DataType> _candleType;

	private Security _benchmark = null!;
	private ExponentialMovingAverage _primaryCarry = null!;
	private ExponentialMovingAverage _benchmarkCarry = null!;
	private SimpleMovingAverage _spreadAverage = null!;
	private StandardDeviation _spreadDeviation = null!;
	private decimal _latestPrimaryCarry;
	private decimal _latestBenchmarkCarry;
	private decimal? _previousZScore;
	private bool _primaryUpdated;
	private bool _benchmarkUpdated;
	private int _cooldownRemaining;

	/// <summary>
	/// Benchmark currency identifier.
	/// </summary>
	public string Security2Id
	{
		get => _security2Id.Value;
		set => _security2Id.Value = value;
	}

	/// <summary>
	/// Smoothing length for the synthetic carry signal.
	/// </summary>
	public int CarryLength
	{
		get => _carryLength.Value;
		set => _carryLength.Value = value;
	}

	/// <summary>
	/// Lookback period used to normalize the carry spread.
	/// </summary>
	public int LookbackPeriod
	{
		get => _lookbackPeriod.Value;
		set => _lookbackPeriod.Value = value;
	}

	/// <summary>
	/// Z-score threshold required to open a position.
	/// </summary>
	public decimal EntryThreshold
	{
		get => _entryThreshold.Value;
		set => _entryThreshold.Value = value;
	}

	/// <summary>
	/// Z-score threshold required to close a position.
	/// </summary>
	public decimal ExitThreshold
	{
		get => _exitThreshold.Value;
		set => _exitThreshold.Value = value;
	}

	/// <summary>
	/// Closed candles to wait before another position change.
	/// </summary>
	public int CooldownBars
	{
		get => _cooldownBars.Value;
		set => _cooldownBars.Value = value;
	}

	/// <summary>
	/// Stop loss percentage.
	/// </summary>
	public decimal StopLoss
	{
		get => _stopLoss.Value;
		set => _stopLoss.Value = value;
	}

	/// <summary>
	/// Candle type for calculations.
	/// </summary>
	public DataType CandleType
	{
		get => _candleType.Value;
		set => _candleType.Value = value;
	}

	public FXCarryTradeStrategy()
	{
		_security2Id = Param(nameof(Security2Id), Paths.HistoryDefaultSecurity2)
			.SetDisplay("Benchmark Security Id", "Identifier of the benchmark currency security", "General");

		_carryLength = Param(nameof(CarryLength), 10)
			.SetRange(2, 80)
			.SetDisplay("Carry Length", "Smoothing length for the synthetic carry signal", "Indicators");

		_lookbackPeriod = Param(nameof(LookbackPeriod), 24)
			.SetRange(5, 120)
			.SetDisplay("Lookback Period", "Lookback period used to normalize the carry spread", "Indicators");

		_entryThreshold = Param(nameof(EntryThreshold), 1.2m)
			.SetRange(0.2m, 5m)
			.SetDisplay("Entry Threshold", "Z-score threshold required to open a position", "Signals");

		_exitThreshold = Param(nameof(ExitThreshold), 0.3m)
			.SetRange(0m, 2m)
			.SetDisplay("Exit Threshold", "Z-score threshold required to close a position", "Signals");

		_cooldownBars = Param(nameof(CooldownBars), 8)
			.SetRange(0, 120)
			.SetDisplay("Cooldown Bars", "Closed candles to wait before another position change", "Risk");

		_stopLoss = Param(nameof(StopLoss), 2.5m)
			.SetRange(0.5m, 10m)
			.SetDisplay("Stop Loss %", "Stop loss percentage", "Risk");

		_candleType = Param(nameof(CandleType), TimeSpan.FromHours(4).TimeFrame())
			.SetDisplay("Candle Type", "Time frame for candles", "General");
	}

	/// <inheritdoc />
	public override IEnumerable<(Security, DataType)> GetWorkingSecurities()
	{
		if (Security != null)
			yield return (Security, CandleType);

		if (!Security2Id.IsEmpty())
			yield return (new Security { Id = Security2Id }, CandleType);
	}

	/// <inheritdoc />
	protected override void OnReseted()
	{
		base.OnReseted();

		_benchmark = null!;
		_primaryCarry = null!;
		_benchmarkCarry = null!;
		_spreadAverage = null!;
		_spreadDeviation = null!;
		_latestPrimaryCarry = 0m;
		_latestBenchmarkCarry = 0m;
		_previousZScore = null;
		_primaryUpdated = false;
		_benchmarkUpdated = false;
		_cooldownRemaining = 0;
	}

	/// <inheritdoc />
	protected override void OnStarted2(DateTime time)
	{
		base.OnStarted2(time);

		if (Security == null)
			throw new InvalidOperationException("Primary security is not specified.");

		if (Security2Id.IsEmpty())
			throw new InvalidOperationException("Benchmark security identifier is not specified.");

		_benchmark = this.LookupById(Security2Id) ?? new Security { Id = Security2Id };
		_primaryCarry = new ExponentialMovingAverage { Length = CarryLength };
		_benchmarkCarry = new ExponentialMovingAverage { Length = CarryLength };
		_spreadAverage = new SimpleMovingAverage { Length = LookbackPeriod };
		_spreadDeviation = new StandardDeviation { Length = LookbackPeriod };

		var primarySubscription = SubscribeCandles(CandleType, security: Security);
		var benchmarkSubscription = SubscribeCandles(CandleType, security: _benchmark);

		primarySubscription
			.Bind(ProcessPrimaryCandle)
			.Start();

		benchmarkSubscription
			.Bind(ProcessBenchmarkCandle)
			.Start();

		var area = CreateChartArea();
		if (area != null)
		{
			DrawCandles(area, primarySubscription);
			DrawCandles(area, benchmarkSubscription);
			DrawOwnTrades(area);
		}

		StartProtection(
			new Unit(2, UnitTypes.Percent),
			new Unit(StopLoss, UnitTypes.Percent));
	}

	private void ProcessPrimaryCandle(ICandleMessage candle)
	{
		if (candle.State != CandleStates.Finished)
			return;

		_latestPrimaryCarry = UpdateCarry(_primaryCarry, candle);
		_primaryUpdated = true;
		TryProcessSpread(candle.OpenTime);
	}

	private void ProcessBenchmarkCandle(ICandleMessage candle)
	{
		if (candle.State != CandleStates.Finished)
			return;

		_latestBenchmarkCarry = UpdateCarry(_benchmarkCarry, candle);
		_benchmarkUpdated = true;
		TryProcessSpread(candle.OpenTime);
	}

	private decimal UpdateCarry(ExponentialMovingAverage average, ICandleMessage candle)
	{
		var carrySignal = CalculateCarrySignal(candle);
		return average.Process(carrySignal, candle.OpenTime, true).ToDecimal();
	}

	private decimal CalculateCarrySignal(ICandleMessage candle)
	{
		var priceBase = Math.Max(candle.OpenPrice, 1m);
		var range = Math.Max(candle.HighPrice - candle.LowPrice, Security?.PriceStep ?? 1m);
		var bodyRatio = (candle.ClosePrice - candle.OpenPrice) / priceBase;
		var stability = 1m - Math.Min(0.2m, range / priceBase);

		return (bodyRatio * 12m) + stability;
	}

	private void TryProcessSpread(DateTime time)
	{
		if (!_primaryUpdated || !_benchmarkUpdated)
			return;

		_primaryUpdated = false;
		_benchmarkUpdated = false;

		var spread = _latestPrimaryCarry - _latestBenchmarkCarry;
		var mean = _spreadAverage.Process(spread, time, true).ToDecimal();
		var deviation = _spreadDeviation.Process(spread, time, true).ToDecimal();

		if (!_spreadAverage.IsFormed || !_spreadDeviation.IsFormed || deviation <= 0m)
			return;

		if (!IsFormedAndOnlineAndAllowTrading())
			return;

		if (_cooldownRemaining > 0)
			_cooldownRemaining--;

		var zScore = (spread - mean) / deviation;
		var bullishEntry = _previousZScore is decimal previousBullish && previousBullish < EntryThreshold && zScore >= EntryThreshold;
		var bearishEntry = _previousZScore is decimal previousBearish && previousBearish > -EntryThreshold && zScore <= -EntryThreshold;

		if (_cooldownRemaining == 0 && Position == 0)
		{
			if (bullishEntry)
			{
				BuyMarket();
				_cooldownRemaining = CooldownBars;
			}
			else if (bearishEntry)
			{
				SellMarket();
				_cooldownRemaining = CooldownBars;
			}
		}
		else if (Position > 0 && zScore <= ExitThreshold)
		{
			SellMarket(Position);
			_cooldownRemaining = CooldownBars;
		}
		else if (Position < 0 && zScore >= -ExitThreshold)
		{
			BuyMarket(Math.Abs(Position));
			_cooldownRemaining = CooldownBars;
		}

		_previousZScore = zScore;
	}
}