PACT: A Runtime Contract for Sparse-Topology Updates in GPU-Accelerated Timing ECOs

Timing ECO flows repeatedly modify circuit topology, yet GPU-accelerated Static Timing Analysis (STA) engines built on static sparse layouts commonly rebuild and resynchronize the GPU-visible topology after each edit. Existing GPU-accelerated STA work instead co-designs dynamic representations with application-specific kernels, exposing representation assumptions to consumers and limiting reuse with CSR-based analyses. We present PACT (Private Atomic Committed Topology), a runtime contract that keeps the mutation representation runtime-private behind a representation-independent committed-traversal contract. GPU traversal consumers observe only a committed CSR-compatible view. PACT maintains this view through a contract-preserving localized commit realization that maps objects created by or incident to each edit batch into affected CSR rows, rematerializes each complete affected CSR row, and exposes the new view after synchronization. Dependency-ordered contract composition applies the same contract to explicit netlist/parasitic edits and timing-state edits derived from their committed frontiers. The selected realization achieves 3.59× the geometric-mean topology-maintenance throughput of a reimplemented Dual-CSR baseline. In an in-house CPU–GPU STA engine, PACT delivers 2.72× and 2.96× end-to-end speedups over full rebuild under two ECO schedules with identical complete timing outputs. Scalability studies further delimit its measured operating range across host thread counts and update-batch sizes.