Chunk 22.0

In this session, the user corrected a fundamental misunderstanding about how the 10 PoRep C2 partitions flow through the proving pipeline. Contrary to my assumption that partitions could be treated as independent ~4s work units, the research agents revealed that each partition actually takes ~32-37s to synthesize (25-27s for witness generation plus 7-10s for SpMV evaluation), and they currently all run in parallel via rayon, finishing simultaneously and submitting to the GPU as a batch. This "thundering herd" approach forces the GPU to wait until all 10 partitions are ready before starting any work, keeps all 10 synthesized partitions in memory at once (~136 GiB), and creates the CPU contention problem when parallel synthesis is attempted. The user's proposed holistic refactor is to break the "10 circuits as a batch" abstraction entirely, treating each partition as an independent work unit that flows through the pipeline one-by-one. Under this model, partition P0 would be dispatched to the GPU immediately upon completion of its synthesis (~32-37s), while P1-P9 are still being synthesized. This would eliminate the vertical handoff stall, reduce memory pressure from 10 partitions to 1-2, and naturally pipeline synthesis across sectors without needing the `synthesis_concurrency` parameter. The partitioned pipeline code path (`prove_porep_c2_partitioned()`) already exists in `pipeline.rs` but currently bypasses the engine-level dispatch, so the next phase would involve refactoring it to emit individual partition `SynthesizedJob` messages through the engine's channel system.

From Thundering Herd to Continuous Pipeline: The Architectural Revolution of the cuzk Proving Engine 2632 words

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