alpha-rl-mbg2n on H100 failed at LobSimCuda::new with
`CUDA_ERROR_NO_BINARY_FOR_GPU` loading book_update.cubin. Root cause:
ml-backtesting/build.rs read only `FOXHUNT_CUDA_ARCH` (set by
lob-backtest-sweep-template) but NOT `CUDA_COMPUTE_CAP` (set by
alpha-rl-template from `nvidia-smi --query-gpu=compute_cap` inside the
compile pod). On H100 it silently fell through to default sm_86; the
sm_86 cubin contains no PTX → no JIT path on sm_90 device.
The docstring claimed "Mirrors crates/ml-alpha/build.rs" — it didn't
(ml-alpha reads CUDA_COMPUTE_CAP). Completing the mirror now: detect_arch
returns sm_<NN> honoring (in order):
1. CUDA_COMPUTE_CAP numeric env (alpha-rl-template)
2. FOXHUNT_CUDA_ARCH sm_-prefixed env (lob-backtest-sweep-template)
3. nvidia-smi --query-gpu=compute_cap at build time
4. Default sm_86 (RTX 3050 Ti local dev)
Both production argo templates now produce sm_90 cubins on H100 and
sm_89 on L40S without further changes.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
build.rs compiles every .cu under crates/ml-backtesting/cuda/ to
\$OUT_DIR/<name>.cubin via nvcc (no nvrtc per feedback_no_nvrtc.md);
pairs every env::var with rerun-if-env-changed per
pearl_build_rs_rerun_if_env_changed.md. Default arch sm_86 (RTX 3050
local); production sets FOXHUNT_CUDA_ARCH=sm_89 (L40S) or sm_90 (H100).
First kernel: book_update_apply_snapshot — block-per-backtest replace
of the 10-level book from a broadcast MBP-10 snapshot. Single-writer
per level (thread tid = level idx), no atomics per feedback_no_atomicadd.md.
lob_state.cuh defines the canonical per-block shared-mem layout that
all subsequent kernels share (Book struct in this commit; Orders, Pos,
IsvKellyState[5] added in C5-C7).
LobSimCuda host struct (in src/sim.rs) constructed from an &MlDevice;
owns per-backtest device book state + mapped-pinned input snapshots.
apply_snapshot launches the kernel and synchronises; read_books drains
device state for tests.
Three Ring 1 fixture tests (book_update_replace, _two_step,
_n_backtests=4) — N≤4 bit-exact GPU oracle assertions loaded from JSON.
All three pass on RTX 3050 locally. Verifies the build-script → cubin →
cudarc.load_cubin → kernel launch → DtoH read pipeline end-to-end.
cudarc added as direct path dep (../../vendor/cudarc) since it's not in
[workspace.dependencies] — same vendored fork ml-alpha uses.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
