LOB 不平衡 Alpha
Lob Imbalance Alpha
题目详情
订单簿不平衡（OBI）量化最优价位的买卖意愿差异，是市场微观结构分析的基础信号。通过测量此压力，可估计短期价格方向和流动性动态。
任务：实现函数计算订单簿不平衡 alpha。OBI = (买量 - 卖量) / (买量 + 卖量)。从多个价位深度计算加权 OBI，返回 -1 到 1 的不平衡指标。
英文原题
Order Book Imbalance (OBI) quantifies the disparity between buy and sell interest at the best price levels, serving as a fundamental signal in market microstructure analysis. By measuring this pressure, quantitative researchers can estimate short-term price directionality and liquidity dynamics essential for high-frequency trading strategies.
Task
Implement a function to calculate the Order Book Imbalance signal and its correlation with future price returns. Given time-series data for best bid
解析
问题分析
Order Book Imbalance (OBI) quantifies the disparity between buy and sell interest at the best price levels, serving as a fundamental signal in market microstructure analysis. By measuring this pressure, quantitative researchers can estimate short-term price directionality and liquidity dynamics esse
解法
根据题目要求实现相应功能。核心逻辑需要：
// 核心数据结构和方法——根据题目 API 约定实现
// 1. 确定状态表示——选择支持所需操作的数据结构
// 2. 实现核心算法——确保 O(·) 时间复杂度和正确性
// 3. 处理边界条件——空输入、极值参数、并发访问验证
用具体输入验证：构造已知输入的测试用例，确认输出匹配预期结果。
复杂度与边界
- 时间复杂度：取决于选用的算法
- 空间复杂度：取决于数据规模
- 关键边界条件：空输入、极值参数、并发场景下的正确性保证
英文解析
Analysis
Order Book Imbalance (OBI) quantifies the disparity between buy and sell interest at the best price levels, serving as a fundamental signal in market microstructure analysis. By measuring this pressure, quantitative researchers can estimate short-term price directionality and liquidity dynamics essential for both alpha generation and execution optimization.
Solution
double computeOBI(const OrderBook& book, int levels = 5) {
double bid_vol = 0, ask_vol = 0;
for (int i = 0; i < levels; ++i) {
bid_vol += book.bidVolume(i);
ask_vol += book.askVolume(i);
}
return (bid_vol - ask_vol) / (bid_vol + ask_vol); // Range: -1 to +1
}
// OBI > 0: buy pressure (price likely to rise)
// OBI < 0: sell pressure (price likely to fall)Complexity & Edge Cases
- Time complexity: O(levels) per computation
- Space complexity: O(1)
- Edge cases: (1) Empty book yields undefined OBI (handle as 0) (2) Deep levels may include stale orders (3) OBI signal decays quickly - must be used within milliseconds
Verification
Compute OBI at each book update, correlate with subsequent 100ms price change. Verify predictive power through regression analysis. Test that OBI correctly identifies buy/sell pressure direction.
Key Considerations
OBI is one of the most robust short-term alpha signals in equity markets. The imbalance at best bid/ask alone captures approximately 5-10bps of predictability for next-second price changes. However, OBI signal decay is rapid - the predictive power halves every 50-100ms, making it only useful for low-latency strategies or execution algorithms.