spec: detailed Phase 2 implementation — workspace isolation, double buffer, determinism
Phase 2a: branch parallel — cuBLAS workspace isolation per branch stream,
buffer isolation verified, backward join before trunk reduction.
Phase 2b: aux parallel — per-trainer workspace (128MB additional), 4 aux
streams, dependency graph within aux_child detailed.
Phase 2c: double buffer — ping-pong experience buffers (3GB additional),
collection/training stream separation, replay buffer staleness analysis,
child graph re-capture for buffer pointer swap.
Determinism: CUDA Graph replay is bit-identical via fixed dependency edges.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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