Prism: Symbolic Superoptimization for Tensors

Optimizing tensor programs for modern AI workloads presents a formidable challenge, often requiring a trade-off between exhaustive search rigor and practical scalability. The researchers behind Prism have introduced a groundbreaking approach to address this dilemma. Their work, detailed on arXiv, unveils Prism, the first symbolic superoptimizer for tensor programs.

Symbolic Graphs for Program Families

The core innovation lies in sGraph, a symbolic, hierarchical representation that compactly encodes vast classes of tensor programs by abstracting execution parameters. Prism leverages this by organizing optimization into a two-level search: first, constructing symbolic graphs representing families of programs, and then instantiating them into concrete implementations. This abstraction allows for structured pruning of provably suboptimal search space regions through symbolic reasoning on operator semantics, algebraic identities, and hardware constraints.

Bridging Rigor and Scalability

By integrating techniques for efficient symbolic graph generation, equivalence verification via e-graph rewriting, and parameter instantiation through auto-tuning, Prism effectively bridges the gap between the precision of exhaustive search and the demands of modern machine learning. The Prism symbolic superoptimizer demonstrated remarkable performance on five common LLM workloads, delivering up to a 2.2x speedup compared to the best superoptimizers and a 4.9x speedup over compiler-based methods. Crucially, it achieved this while reducing end-to-end optimization time by up to 3.4x, showcasing a significant leap in efficiency.