Cache all hot-path device pointers as raw u64 in HotPathPtrs struct at
trainer init. Replaces 9 device_ptr()/device_ptr_mut() calls (each
triggers cudarc event wait+record → cuStreamSynchronize) with direct
u64 reads from the cached struct.
Affected call sites:
- ISV staging DtoD (step_synthetic)
- Batched loss readback: pi/Q/V/FRD DtoD copies (step_synthetic)
- h_t→h_tp1 encoder DtoD copy (step_with_lobsim)
- trade_context/multires_output ptr pass to perception encoder
All pointers are stable (buffers pre-allocated at init, never
reallocated). Utility functions (read_slice_d, write_slice_f32_d, etc.)
retain device_ptr() as they operate on arbitrary caller-provided buffers
and each already does its own stream sync.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
4a4e3171a7