Per feedback_no_htod_htoh_only_mapped_pinned.md (newly recorded): every
CPU<->GPU path in this redesign uses mapped pinned memory exclusively.
No cudaMemcpy HtoD, no Vec-to-Vec defensive copies, including in test
code. CPU is strictly read-only on the production surface.
Plan changes:
- New Task 2.0 promotes MappedF32Buffer / MappedI32Buffer from
distributional_q_tests.rs local definitions to a shared
crates/ml/src/cuda_pipeline/mapped_pinned.rs module so all kernel
test wrappers (Test 0.F, upcoming MoE tests) share one
implementation. Adds write_from_slice helper for direct host_ptr
write (no memcpy).
- Task 2.1 test wrapper rewritten to allocate mapped pinned buffers
+ write to host_ptr + read GPU-written output via host_ptr. No more
memcpy_stod / memcpy_dtov in test code.
Spec: new section 6.4 codifies the mapped-pinned-only constraint and
references the shared module + reference implementation.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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