start experiment 38 (exp/38-q06-kelly-sizing-score-magnitude-fractio)

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zhaoli
2026-08-19 23:28:29 +00:00
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"""Fractional-Kelly dropout strategy for cross-sectional signals.
Sizing rule variant of ``qlib.contrib.strategy.signal_strategy.TopkDropoutStrategy``:
the topk/n_drop SELECTION is identical to the reference, but the buy size is
proportional to the score MAGNITUDE (edge) instead of equal-weight, capped at a
fraction ``cap_frac`` of the equal-weight notional so a single name cannot
over-concentrate the book.
``cap_frac`` is the fraction of the equal-weight per-name notional that a top
signal can deploy at most (e.g. 0.5 = at most half the equal-weight size).
Names whose score is below the median of the buy set get a proportionally
smaller slice; the residual stays in cash (that is the point of the rule:
throw away less edge per name, deploy less capital when conviction is low).
"""
from __future__ import annotations
from typing import List
import numpy as np
import pandas as pd
from qlib.backtest import Order
from qlib.backtest.decision import OrderDir, TradeDecisionWO
from qlib.contrib.strategy.signal_strategy import TopkDropoutStrategy
__all__ = ["FractionalKellyDropoutStrategy"]
DEFAULT_CAP_FRAC = 0.5
class FractionalKellyDropoutStrategy(TopkDropoutStrategy):
"""TopkDropout selection with score-magnitude (fractional-Kelly) sizing.
Parameters
----------
topk, n_drop, method_sell, method_buy, hold_thresh, only_tradable,
forbid_all_trade_at_limit : same as ``TopkDropoutStrategy``.
cap_frac : max buy notional as a fraction of the equal-weight notional.
"""
def __init__(self, *, topk, n_drop, cap_frac: float = DEFAULT_CAP_FRAC, **kwargs):
super().__init__(topk=topk, n_drop=n_drop, **kwargs)
self.cap_frac = cap_frac
def generate_trade_decision(self, execute_result=None):
import copy
trade_step = self.trade_calendar.get_trade_step()
trade_start_time, trade_end_time = self.trade_calendar.get_step_time(trade_step)
pred_start_time, pred_end_time = self.trade_calendar.get_step_time(trade_step, shift=1)
pred_score = self.signal.get_signal(start_time=pred_start_time, end_time=pred_end_time)
if isinstance(pred_score, pd.DataFrame):
pred_score = pred_score.iloc[:, 0]
if pred_score is None:
return TradeDecisionWO([], self)
if self.only_tradable:
def get_first_n(li, n, reverse=False):
cur_n = 0
res = []
for si in reversed(li) if reverse else li:
if self.trade_exchange.is_stock_tradable(
stock_id=si, start_time=trade_start_time, end_time=trade_end_time
):
res.append(si)
cur_n += 1
if cur_n >= n:
break
return res[::-1] if reverse else res
def get_last_n(li, n):
return get_first_n(li, n, reverse=True)
def filter_stock(li):
return [
si
for si in li
if self.trade_exchange.is_stock_tradable(
stock_id=si, start_time=trade_start_time, end_time=trade_end_time
)
]
else:
def get_first_n(li, n):
return list(li)[:n]
def get_last_n(li, n):
return list(li)[-n:]
def filter_stock(li):
return li
current_temp: "object" = copy.deepcopy(self.trade_position)
sell_order_list: List[Order] = []
buy_order_list: List[Order] = []
cash = current_temp.get_cash()
current_stock_list = current_temp.get_stock_list()
last = pred_score.reindex(current_stock_list).sort_values(ascending=False).index
if self.method_buy == "top":
today = get_first_n(
pred_score[~pred_score.index.isin(last)].sort_values(ascending=False).index,
self.n_drop + self.topk - len(last),
)
elif self.method_buy == "random":
topk_candi = get_first_n(pred_score.sort_values(ascending=False).index, self.topk)
candi = list(filter(lambda x: x not in last, topk_candi))
n = self.n_drop + self.topk - len(last)
try:
today = np.random.choice(candi, n, replace=False)
except ValueError:
today = candi
else:
raise NotImplementedError(f"This type of input is not supported")
comb = pred_score.reindex(last.union(pd.Index(today))).sort_values(ascending=False).index
if self.method_sell == "bottom":
sell = last[last.isin(get_last_n(comb, self.n_drop))]
elif self.method_sell == "random":
candi = filter_stock(last)
try:
sell = pd.Index(np.random.choice(candi, self.n_drop, replace=False) if len(last) else [])
except ValueError:
sell = candi
else:
raise NotImplementedError(f"This type of input is not supported")
buy = today[: len(sell) + self.topk - len(last)]
for code in current_stock_list:
if not self.trade_exchange.is_stock_tradable(
stock_id=code,
start_time=trade_start_time,
end_time=trade_end_time,
direction=None if self.forbid_all_trade_at_limit else OrderDir.SELL,
):
continue
if code in sell:
time_per_step = self.trade_calendar.get_freq()
if current_temp.get_stock_count(code, bar=time_per_step) < self.hold_thresh:
continue
sell_amount = current_temp.get_stock_amount(code=code)
sell_order = Order(
stock_id=code,
amount=sell_amount,
start_time=trade_start_time,
end_time=trade_end_time,
direction=Order.SELL,
)
if self.trade_exchange.check_order(sell_order):
sell_order_list.append(sell_order)
trade_val, trade_cost, trade_price = self.trade_exchange.deal_order(
sell_order, position=current_temp
)
cash += trade_val - trade_cost
if len(buy) == 0:
return TradeDecisionWO(sell_order_list, self)
# ---- fractional-Kelly sizing --------------------------------------
# equal-weight notional (reference baseline)
eq_notional = cash * self.risk_degree / len(buy)
buy_scores = pred_score.reindex(buy).astype(float)
lo, hi = buy_scores.min(), buy_scores.max()
if hi == lo:
w = pd.Series(1.0, index=buy_scores.index)
else:
w = (buy_scores - lo) / (hi - lo) # [0,1] edge magnitude
w = w.clip(lower=0.0)
w_max = w.max()
w = w / w_max if w_max > 0 else w # max == 1.0
for code in buy:
if not self.trade_exchange.is_stock_tradable(
stock_id=code,
start_time=trade_start_time,
end_time=trade_end_time,
direction=None if self.forbid_all_trade_at_limit else OrderDir.BUY,
):
continue
buy_price = self.trade_exchange.get_deal_price(
stock_id=code, start_time=trade_start_time, end_time=trade_end_time, direction=OrderDir.BUY
)
notional = eq_notional * min(self.cap_frac, float(w.get(code, 0.0)))
buy_amount = notional / buy_price
factor = self.trade_exchange.get_factor(
stock_id=code, start_time=trade_start_time, end_time=trade_end_time
)
buy_amount = self.trade_exchange.round_amount_by_trade_unit(buy_amount, factor)
buy_order = Order(
stock_id=code,
amount=buy_amount,
start_time=trade_start_time,
end_time=trade_end_time,
direction=Order.BUY,
)
buy_order_list.append(buy_order)
return TradeDecisionWO(sell_order_list + buy_order_list, self)