Chunk 20.0

## Summary This chunk focused on end-to-end testing and analysis of the cuzk proving daemon's pipeline performance. The assistant first verified that all phases (PCE, pipelined partition proving) were properly wired into the daemon, then ran comprehensive e2e benchmarks using the daemon's gRPC interface. The key discovery was that the standard pipeline path (`slot_size=0`) dramatically outperformed the partitioned path (~47.7s/proof vs ~72s/proof) because it uses the engine's two-stage architecture where synthesis of proof N+1 overlaps with GPU proving of proof N via the synthesis task → GPU channel pipeline. The partitioned path blocked the synthesis task for the entire proof duration, preventing any inter-proof overlap. A throughput benchmark varying `-j` concurrency (1, 2, 3, 5) revealed that GPU utilization saturates at ~57% with `-j >= 2`, achieving 1.3 proofs/min. The bottleneck is synthesis time (~38s) exceeding GPU time (~26s), leaving a ~12s GPU idle gap between proofs. Testing `synthesis_lookahead=2` helped but didn't fully close the gap since synthesis remains the longer phase. The partitioned path's value proposition shifted from throughput improvement to memory reduction (71 GiB vs 228 GiB peak), making it suitable for memory-constrained deployments while the standard pipeline remains optimal for throughput. The overarching theme is that the existing engine pipeline already achieves near-optimal GPU utilization through inter-proof overlap, and the partitioned path's primary benefit is memory efficiency rather than throughput. The analysis identified that further GPU utilization gains would require either reducing synthesis time (already near-minimum with PCE) or running multiple synthesis tasks in parallel—a significant engine architecture change.

The Great Unwinding: How End-to-End Testing Revealed the True Value of a Pipelined Proving Architecture 2574 words

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