Four new kernels in mamba2_alpha_kernel.cu:
- backtest_per_trade_pnl : [T, N] per-trade PnL with threshold filter
- backtest_sum_reduce_f32 : block tree-reduce returns per threshold (T scalars)
- backtest_sum_squared_reduce : block tree-reduce returns² per threshold (T scalars)
- backtest_sum_reduce_i32 : block tree-reduce trade counts per threshold
All atomicAdd-free via block tree-reduce in shared memory (per
feedback_no_atomicadd). Single kernel launch handles the full
threshold sweep across all sequences via grid_x=T, grid_y=ceil(N/256).
New module crates/ml-alpha/src/backtest.rs:
- GpuBacktest::from_block(&Mamba2Block) — reuses cubin already loaded
- GpuBacktest::run(probs, prices_t, prices_kt, thresholds, cost) → Vec<BacktestStats>
- Returns: n_trades, mean_ret, std_ret, Sharpe (per-trade unannualised),
hit_rate, total_pnl per threshold
Wired into phase1d_long_horizon.rs after the stacker eval:
- Convert stacker_logits → probs via sigmoid
- Upload probs + end-bar prices + (end-bar + horizon) prices to GPU
- Sweep thresholds [0.00, 0.02, 0.05, 0.10, 0.15, 0.20, 0.25]
- Print per-threshold table + best Sharpe operating point
- GATE: per-trade Sharpe > 1.5 = deployable, 0.5-1.5 = marginal, < 0.5 = fail
Cost model: 0.25 price units round-trip = 1 ES.FUT tick = $12.50/contract.
Tunable via --cost-per-trade. Realistic for retail flow; brokers can
trade at half-tick or better.
GPU-pure on the hot path: kernels do per-trade math + reductions;
host only receives T (= 7 here) scalars per metric for final Sharpe
arithmetic. No GPU↔CPU roundtrip per trade.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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