Migrates target_annual_vol_units, annualisation_factor, max_lots,
latency_ns, kelly_frac_floor, sharpe_weight_floor from scalar-broadcast
kernel args to per-backtest device arrays via BatchedSimConfig. Atomic
contract change per feedback_no_partial_refactor — kernel + sim + harness
+ all 3 existing test files migrate in this commit.
- crates/ml-backtesting/src/sim.rs → sim/mod.rs (directory module)
- crates/ml-backtesting/src/sim/batched_config.rs (NEW): BatchedSimConfig
+ UniformSimParams + validate(). from_uniform rebuilds the legacy
uniform-broadcast behaviour at n=1 (smoke/fixtures). from_grid lands
in P6 for the 140-variant sweep packing.
- LobSimCuda gains 6 per-backtest device buffers (target_annual_vol_units_d,
annualisation_factor_d, max_lots_d, latency_ns_d, kelly_frac_floor_d,
sharpe_weight_floor_d). step_decision_with_latency uploads from
BatchedSimConfig each call; both decision kernel launches now pass
per-backtest array pointers.
- decision_policy_default + decision_policy_program: scalar args become
const float* / const int* per_b arrays; first lines of each kernel
index by `b` into the arrays. Behaviour preserved at n=1 uniform.
- dispatch_latent_market_orders: reads latency per-backtest from
&BatchedSimConfig (host loop stays for P1; P2 replaces with kernel).
- step_decision_with_latency now ALWAYS dispatches through the latency
path; when cfg.latency_ns[b]=0 the in-flight slot's arrival_ts equals
current_ts and gets promoted immediately on next snapshot. Eliminates
the if/else branch and consolidates the launch path.
- harness.rs: BacktestHarness gains a sim_config field, built via
BatchedSimConfig::from_uniform at new() from the harness cfg's scalar
fields. The run loop passes &self.sim_config to step_decision_with_latency.
Regression coverage:
- parallel_sim_correctness::parallel_sim_equivalence_with_uniform_config
— n=8 with uniform config produces 8 bit-identical market_targets
(proves per-backtest indexing reduces correctly).
- Existing decision_floor_coldstart tests (3) all pass through the new
ABI — proves cold-start floor + variance-cap gate behaviour preserved.
- parallel_sim_independence_per_backtest deferred to P2 (needs
read_first_inflight_arrival_ts helper that depends on LimitSlot layout).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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