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Currency PPP Value Strategy

The Currency PPP Value strategy looks for mispricing relative to purchasing power parity (PPP). Currencies that trade below their PPP value are bought, while those trading above their PPP value are shorted. The portfolio is rebalanced monthly to maintain the long/short exposure.

Because PPP data updates infrequently, trades are only placed when the required adjustment exceeds a minimum USD amount. The sample code provides the framework for ranking currencies but leaves the actual PPP calculation as a placeholder.

Details

  • Universe: Set of currency pairs with available PPP estimates.
  • Signal: Long the K most undervalued currencies and short the K most overvalued.
  • Rebalance: Monthly.
  • Positioning: Long/short, equal weight.
  • Parameters:
    • Universe – tradable currencies.
    • K – number of currencies to long and short.
    • MinTradeUsd – minimum trade size in USD.
    • CandleType – candle timeframe (default: 1 day).
  • Note: PPP deviation retrieval (TryGetPPPDeviation) is not implemented and must be supplied by the user.
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>
/// Currency PPP value strategy that trades the primary instrument when its synthetic PPP deviation becomes extreme relative to a benchmark currency.
/// </summary>
public class CurrencyPppValueStrategy : Strategy
{
	private readonly StrategyParam<string> _security2Id;
	private readonly StrategyParam<int> _pppLength;
	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 _primaryPpp = null!;
	private ExponentialMovingAverage _benchmarkPpp = null!;
	private SimpleMovingAverage _spreadAverage = null!;
	private StandardDeviation _spreadDeviation = null!;
	private decimal _latestPrimaryDeviation;
	private decimal _latestBenchmarkDeviation;
	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 PPP anchor.
	/// </summary>
	public int PppLength
	{
		get => _pppLength.Value;
		set => _pppLength.Value = value;
	}

	/// <summary>
	/// Lookback period used to normalize the deviation 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 used for both instruments.
	/// </summary>
	public DataType CandleType
	{
		get => _candleType.Value;
		set => _candleType.Value = value;
	}

	/// <summary>
	/// Constructor.
	/// </summary>
	public CurrencyPppValueStrategy()
	{
		_security2Id = Param(nameof(Security2Id), Paths.HistoryDefaultSecurity2)
			.SetDisplay("Benchmark Security Id", "Identifier of the benchmark currency security", "General");

		_pppLength = Param(nameof(PppLength), 14)
			.SetRange(2, 80)
			.SetDisplay("PPP Length", "Smoothing length for the synthetic PPP anchor", "Indicators");

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

		_entryThreshold = Param(nameof(EntryThreshold), 1.25m)
			.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 of candles", "General");
	}

	/// <inheritdoc />
	public override IEnumerable<(Security sec, DataType dt)> 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!;
		_primaryPpp = null!;
		_benchmarkPpp = null!;
		_spreadAverage = null!;
		_spreadDeviation = null!;
		_latestPrimaryDeviation = 0m;
		_latestBenchmarkDeviation = 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 currency security is not specified.");

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

		_benchmark = this.LookupById(Security2Id) ?? new Security { Id = Security2Id };
		_primaryPpp = new ExponentialMovingAverage { Length = PppLength };
		_benchmarkPpp = new ExponentialMovingAverage { Length = PppLength };
		_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;

		_latestPrimaryDeviation = UpdateDeviation(_primaryPpp, candle);
		_primaryUpdated = true;
		TryProcessSpread(candle.OpenTime);
	}

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

		_latestBenchmarkDeviation = UpdateDeviation(_benchmarkPpp, candle);
		_benchmarkUpdated = true;
		TryProcessSpread(candle.OpenTime);
	}

	private decimal UpdateDeviation(ExponentialMovingAverage average, ICandleMessage candle)
	{
		var syntheticPpp = CalculateSyntheticPpp(candle);
		var pppAnchor = average.Process(syntheticPpp, candle.OpenTime, true).ToDecimal();

		return (candle.ClosePrice - pppAnchor) / Math.Max(pppAnchor, 1m);
	}

	private decimal CalculateSyntheticPpp(ICandleMessage candle)
	{
		var priceBase = Math.Max(candle.OpenPrice, 1m);
		var range = Math.Max(candle.HighPrice - candle.LowPrice, Security?.PriceStep ?? 1m);
		var purchasingPowerAnchor = (candle.OpenPrice + candle.LowPrice + candle.ClosePrice) / 3m;
		var inflationPenalty = priceBase * Math.Min(0.12m, range / priceBase);

		return purchasingPowerAnchor - inflationPenalty;
	}

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

		_primaryUpdated = false;
		_benchmarkUpdated = false;

		var spread = _latestPrimaryDeviation - _latestBenchmarkDeviation;
		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;
	}
}