Decision-stride S lets a length-K sequence span ((K-1)*S + 1) raw
snapshots instead of K consecutive ones — expands the effective
time-window covered by each sequence at the same K-positions compute
cost. With K=64 and S=4, the window covers 256 ticks (~5s on ES MBP-10
at 20ms-tick) instead of 64 ticks (~1.3s).
Loader (crates/ml-alpha/src/data/loader.rs):
- `MultiHorizonLoaderConfig.decision_stride: usize` (default 1, must
pre-existing call sites add the new field).
- `next_sequence` reads snapshot at `anchor + k * stride`; labels at the
same indices (labels stay in absolute-snapshot horizons regardless of
stride, e.g. h=6000 always means "predict 6000 raw snapshots forward").
- `prev` snapshot for microstructure features (prev_mid, prev_ts_ns)
now points to the prior K-position (`anchor + (k-1)*stride`), NOT the
consecutive-snapshot prior, so `Δt = ts_ns - prev_ts_ns` carries the
actual elapsed time between K-positions (consumed by Mamba2's dt_s and
the planned Phase 2C TGN Fourier features).
- New `#[ignore]` real-data test: `loader_stride_4_yields_correct_spacing`
asserts Δt monotonicity at stride=4.
Mamba2 dt_s (crates/ml-alpha/src/trainer/perception.rs):
- `PerceptionTrainerConfig.decision_stride: usize` plumbs the stride
through. dispatch_train_step + evaluate_batched now use
`dt_s = decision_stride as f32` so Mamba2's selective scan
`exp(-dt * sigmoid(a))` reflects the real elapsed time. With stride=1
the behaviour is identical to before.
CLI (crates/ml-alpha/examples/alpha_train.rs):
- `--decision-stride <S>` flag (default 1) wired into both train and val
loaders + PerceptionTrainerConfig.
Argo workflow:
- `decision-stride` parameter on the template (default "1") +
`--decision-stride` script flag + propagation into the train pod's
alpha_train invocation.
Synthetic smoke (tests/perception_overfit.rs):
- `stacked_trainer_loss_shrinks_with_stride_4` proves the trainer-level
dt_s=4.0 keeps the Mamba2+LN+CfC+GRN chain numerically stable.
Converges 0.32 → 0.0000 (matches stride=1 smoke trajectory — dt_s
scaling didn't break the SSM dynamics).
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
70d5fc29cf