Chunk 15.1

In this chunk, the assistant investigated the user's hypothesis that allocation overhead during synthesis might mirror the previously fixed deallocation bottleneck. Tracing the growth of `ProvingAssignment` Vecs (`a`, `b`, `c`, `aux_assignment`) in bellperson, the assistant found that while a `SynthesisCapacityHint` API for pre-allocation already existed, it was never wired up in the pipeline callers, forcing the Vecs to grow organically via `push()` through ~27 reallocation cycles each. The assistant implemented a global hint cache and modified all six synthesis call sites in `pipeline.rs` to use `synthesize_circuits_batch_with_hint`, theoretically eliminating ~265 GB of redundant memory copies across 10 parallel circuits. This infrastructure was committed as a defensive optimization. Despite the strong theoretical motivation, rigorous benchmarking (single-partition synth-only and full E2E with the daemon) showed **zero measurable impact** (50.65s synthesis time with and without hints). The themes of this chunk are hypothesis-driven optimization, the critical importance of measurement over intuition, and the fundamental asymmetry of alloc vs dealloc: Rust's geometric `push()` amortizes cost and overlaps with parallel computation, while the previous dealloc win came from synchronous `munmap` of large GPU-phase buffers. This confirms the synthesis bottleneck is purely computational, reinforcing the necessity of Phase 5 (PCE) for significant gains.

The Allocation Hypothesis: When a Quarter-Terabyte of Wasted Copies Changed Nothing 2561 words

Message Articles

Subagent Sessions