Replaced the CPU validation path (compute_validation_loss) with the
existing GpuBacktestEvaluator. The CPU path downloaded Q-values to host,
did argmax + PnL + Sharpe on CPU — 2s/epoch from the GPU→CPU sync.
The GPU evaluator does everything on-device: cuBLAS forward, argmax,
PnL simulation, Sharpe/drawdown/PF computation. Lazy-initialized once
per fold from val_data, called each epoch with current weights.
Deleted:
- val_features_gpu, val_closes_gpu, val_ofi_gpu fields (CPU caches)
- CPU state tensor assembly (80-line loop)
- clone_htod_f32_to_bf16 upload
- dtoh_bf16_to_f32 download + GPU→CPU sync
- CPU argmax loop
- CPU Sharpe computation
- Epsilon save/restore
Net -61 lines of dead CPU code.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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