submit_market_immediate walks the ask/bid book for a buy/sell market
order, computes notional cost + filled lots across up to 10 levels,
and updates per-backtest Pos { position_lots, vwap_entry, realized_pnl }
with correct VWAP scale-in + counter-direction realized-P&L accounting.
Single-writer (thread 0) per block — no atomics per
feedback_no_atomicadd.md. Each backtest gets its own target slot
{ side, size } in the device-global targets array (side=2 = no-op).
Pos struct added to lob_state.cuh (24 bytes); host mirror PosFlat in
src/lob/mod.rs is repr(C) bytemuck::Pod for direct host↔device cast.
LobSimCuda gains submit_market(backtest_idx, side, size) +
read_pos(backtest_idx) -> PosFlat. Fixture harness extended with the
SubmitMarket event variant + ExpectedPos check (vwap_tol + realized_pnl_tol
for FP tolerance).
market_order_consumes_top fixture verifies a buy of 5 lots into
ask[3@5500.00, 10@5500.25] fills 3+2 → position_lots=5,
vwap_entry=5500.10 within 1e-3 tolerance. All 4 Ring 1 fixtures
(book_update × 3 + market_order × 1) green on RTX 3050.
Scope deliberately trimmed from plan C5: this commit lands market-fill
matching only. Queue decay on resting limits, in-flight latency
promotion, stop-trigger detection, and OCO leg-cancellation will land
in follow-up commits — each in its own kernel addition. This keeps the
incremental delta reviewable.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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