Registry indexed
Event-driven backtesting with realistic order execution, position tracking, and performance measurement. Use when simulating a trading strategy on historical data.
Event-driven backtesting with realistic order execution, position tracking, and performance measurement. Use when simulating a trading strategy on historical data.
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Vectorized backtests hide execution reality. Event-driven simulation processes each bar sequentially, submitting orders that fill at future prices - the only way to model what actually happens when you trade.
Vectorized positions * returns backtests assume instant fills at known prices. In reality, you decide to trade on bar t but fill at bar t+1. Ignoring this inflates Sharpe by 0.3-0.5 or more for daily strategies. The faster the signal, the larger the gap.
# Vectorized: signal and fill use the SAME bar's price
signals = compute_signal(prices) # uses close[t]
positions = np.where(signals > 0, 1, 0) # no shift!
returns = prices.pct_change()
strategy_returns = positions * returns # lookahead: traded at price used to decide
sharpe = strategy_returns.mean() / strategy_returns.std() * np.sqrt(252)
import numpy as np
def event_backtest(prices: np.ndarray, signal_fn, cost_bps: float = 10):
"""Minimal event-driven backtest: decide on bar t, fill on bar t+1."""
n = len(prices)
cash, shares = 100_000.0, 0
equity = np.zeros(n)
for t in range(1, n):
# Fill yesterday's order at today's open
target = signal_fn(prices[:t]) # can only see past
current_shares = shares
trade = target - current_shares
if trade != 0:
fill_price = prices[t] # next bar (simulating open)
cost = abs(trade * fill_price) * cost_bps / 10_000
cash -= trade * fill_price + cost
shares += trade
equity[t] = cash + shares * prices[t]
returns = np.diff(equity[1:]) / equity[1:-1]
sharpe = returns.mean() / returns.std() * np.sqrt(252)
return equity, sharpe
signal_fn(prices[:t]) sees only past barsSAME_BAR close is optimistic - prefer next-bar open for daily strategies (close-to-open gap is 50-100 bps on equities)ml4t-backtest provides a validated event-driven engine:
from ml4t.backtest import (
Strategy, Engine, DataFeed, BacktestConfig,
)
class Momentum(Strategy):
def on_data(self, timestamp, data, context, broker):
for sym, bar in data.items():
if bar["signals"].get("momentum", 0) > 0 and not broker.get_position(sym):
size = int(broker.get_cash() * 0.1 / bar["close"])
broker.submit_order(sym, size)
feed = DataFeed(prices_df=prices, signals_df=signals)
config = BacktestConfig(commission_rate=0.001, slippage_rate=0.001)
result = Engine(feed, Momentum(), config).run()
print(f"Sharpe: {result.metrics['sharpe']:.2f} MaxDD: {result.metrics['max_drawdown']:.1%}")
prices[:t])name: ml4t-run-backtest description: "Event-driven backtesting with realistic order execution, position tracking, and performance measurement. Use when simulating a trading strategy on historical data." when_to_use: "Use when simulating a strategy bar-by-bar with fills, positions, and costs" dependencies: [cost-model] metadata: book_chapters: "16" library: "ml4t-backtest" paths: ["**/*backtest*.py", "**/*strategy*.py", "**/*engine*.py", "**/*broker*.py", "**/*cost*.py", "**/*regime*.py", "**/*tearsheet*.py"]
---
name: ml4t-run-backtest
description: "Event-driven backtesting with realistic order execution, position tracking, and performance measurement. Use when simulating a trading strategy on historical data."
when_to_use: "Use when simulating a strategy bar-by-bar with fills, positions, and costs"
dependencies: [cost-model]
metadata:
book_chapters: "16"
library: "ml4t-backtest"
paths: ["**/*backtest*.py", "**/*strategy*.py", "**/*engine*.py", "**/*broker*.py", "**/*cost*.py", "**/*regime*.py", "**/*tearsheet*.py"]
---
# Event-Driven Backtesting
Vectorized backtests hide execution reality. Event-driven simulation processes each bar sequentially, submitting orders that fill at future prices - the only way to model what actually happens when you trade.
## The Problem
Vectorized `positions * returns` backtests assume instant fills at known prices. In reality, you decide to trade on bar _t_ but fill at bar _t+1_. Ignoring this inflates Sharpe by 0.3-0.5 or more for daily strategies. The faster the signal, the larger the gap.
## The Pattern
### WRONG
```python
# Vectorized: signal and fill use the SAME bar's price
signals = compute_signal(prices) # uses close[t]
positions = np.where(signals > 0, 1, 0) # no shift!
returns = prices.pct_change()
strategy_returns = positions * returns # lookahead: traded at price used to decide
sharpe = strategy_returns.mean() / strategy_returns.std() * np.sqrt(252)
```
### CORRECT
```python
import numpy as np
def event_backtest(prices: np.ndarray, signal_fn, cost_bps: float = 10):
"""Minimal event-driven backtest: decide on bar t, fill on bar t+1."""
n = len(prices)
cash, shares = 100_000.0, 0
equity = np.zeros(n)
for t in range(1, n):
# Fill yesterday's order at today's open
target = signal_fn(prices[:t]) # can only see past
current_shares = shares
trade = target - current_shares
if trade != 0:
fill_price = prices[t] # next bar (simulating open)
cost = abs(trade * fill_price) * cost_bps / 10_000
cash -= trade * fill_price + cost
shares += trade
equity[t] = cash + shares * prices[t]
returns = np.diff(equity[1:]) / equity[1:-1]
sharpe = returns.mean() / returns.std() * np.sqrt(252)
return equity, sharpe
```
## Key Execution Rules
1. **Signal on bar _t_, fill on bar _t+1_** - never fill at the price you used to decide
2. **Track cash and positions explicitly** - position * price = equity, not magic
3. **Deduct costs per trade** - commission + spread + slippage on every fill
4. **No fractional knowledge** - `signal_fn(prices[:t])` sees only past bars
## Guardrails
- Fill at `SAME_BAR` close is optimistic - prefer next-bar open for daily strategies (close-to-open gap is 50-100 bps on equities)
- Any Sharpe above 2.0 on daily data warrants checking for fill-timing bugs
- Position sizing must respect available cash (no implicit margin)
- Watch for survivorship bias in the universe - delisted symbols vanish from data
## Production Implementation
`ml4t-backtest` provides a validated event-driven engine:
```python
from ml4t.backtest import (
Strategy, Engine, DataFeed, BacktestConfig,
)
class Momentum(Strategy):
def on_data(self, timestamp, data, context, broker):
for sym, bar in data.items():
if bar["signals"].get("momentum", 0) > 0 and not broker.get_position(sym):
size = int(broker.get_cash() * 0.1 / bar["close"])
broker.submit_order(sym, size)
feed = DataFeed(prices_df=prices, signals_df=signals)
config = BacktestConfig(commission_rate=0.001, slippage_rate=0.001)
result = Engine(feed, Momentum(), config).run()
print(f"Sharpe: {result.metrics['sharpe']:.2f} MaxDD: {result.metrics['max_drawdown']:.1%}")
```
## Checklist
- [ ] Orders fill at a future bar, not the decision bar
- [ ] Signal function sees only past data (`prices[:t]`)
- [ ] Commission and slippage deducted on every fill
- [ ] Cash balance tracked - no implicit leverage
- [ ] Sharpe < 2.0 on daily data (or justified)
Free to get does not mean free to run. Price labels are not safety ratings. Submit pricing information →
Skill source recorded
Skill instructions are recorded. This is not a runtime test, safety guarantee or compatibility certification.
Review before install: Avoid automatic install
License: Apache-2.0
Listed tools are metadata hints, not tested compatibility. Agent prompts are suggested handoffs.
Check the source for dependencies, API keys and third-party costs. A public repository does not mean every service is free.
Repository metadata and review signals are advisory. Popularity, source discovery and successful execution are different facts.
Version reported in registry metadata; check source releases before relying on it.
Quality
54/100
Needs review
Trust
66/100
Sandbox only
Audit
75/100
Risky
Copies are not installs. Installation counts require a reported successful installation; they are not a blanket quality guarantee.
This page exposes the same decision, trust, audit, use-case, and install signals through the Registry API, so agents can rank this skill without scraping the UI.
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