NOVA: Coordinated Test Selection and Bayes-Optimized Constrained Randomization for Accelerated Coverage Closure

TL;DR

NOVA is a framework that combines coverage-aware test selection with Bayesian-optimized constrained randomization to significantly accelerate coverage convergence in RTL verification, reducing simulation time without manual heuristics.

Contribution

NOVA introduces a coordinated approach that integrates coverage-based test filtering with Bayesian optimization of randomization constraints, improving verification efficiency.

Findings

Up to 2.82× coverage speedup across multiple RTL designs.

Automated parameter tuning reduces manual effort in test generation.

Effective coverage growth without relying on handcrafted heuristics.

Abstract

Functional verification relies on large simulation-based regressions. Traditional test selection relies on static test features and overlooks actual coverage behavior, wasting substantial simulation time, while constrained random stimuli generation depends on manually crafted distributions that are difficult to design and often ineffective. We present NOVA, a framework that coordinates coverage-aware test selection with Bayes-optimized constrained randomization. NOVA extracts fine-grained coverage features to filter redundant tests and modifies the constraint solver to expose parameterized decision strategies whose settings are tuned via Bayesian optimization to maximize coverage growth. Across multiple RTL designs, NOVA achieves up to a 2.82$\times$ coverage convergence speedup without requiring human-crafted heuristics.