Segment 23

This sub-session completed the implementation of Phase 7 of the cuzk proving engine, following the detailed specification in c2-optimization-proposal-7.md. The agent extended data structures, refactored dispatch logic to use a semaphore-gated pool of spawn_blocking workers, added partition-aware GPU routing, and integrated error handling and memory management. Initial benchmarks showed improved throughput (~45-50s/proof) but revealed jumpy GPU utilization. Deep performance analysis traced the root cause to a static std::mutex in generate_groth16_proofs_c that holds for the entire ~3.5s function, with only ~2.1s being actual CUDA kernel execution. This diagnosis led to the design of Phase 8, documented in c2-optimization-proposal-8.md, proposing a dual-GPU-worker interlock that allows CPU preamble/epilogue to overlap with GPU kernels, promising to boost GPU efficiency from ~64% to ~98% and yield 3-10% throughput improvement. Both the Phase 7 implementation and Phase 8 design document were committed to the feat/cuzk branch.

From Per-Partition Pipeline to Dual-GPU Interlock: The Phase 7–8 Journey in the cuzk Proving Engine 2944 words

Chunks

• From Architecture to Diagnosis: The Phase 7 Journey Through Implementation, Benchmarking, and the Discovery of Phase 8
  1590 words
• From Diagnosis to Design: How a 64.3% GPU Efficiency Number Drove Phase 8 of the cuzk Proving Engine
  2117 words