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A Formal Characterization of Non-Monotonicity in Tensor Cores


Poster Type: ACM Student Research Competition, Undergraduate

Author: Paul Jiang (Purdue University), Vivian Zheng (Stony Brook University)

Supervisor: Ganesh Gopalakrishnan (University of Utah)

Abstract: Modern high performance computing increasingly relies on hardware accelerators like NVIDIA Tensor Cores, which employ non-standard internal arithmetic that can evolve between hardware generations. This non-standard approach can violate the fundamental mathematical property of monotonicity, leading to incorrect outputs where adding a larger number produces a smaller result. To address this, we introduce a formal framework using satisfiability modulo theories to analyze the hardware design space by systematically varying hardware features (e.g., number of terms [𝑛], internal padding bits [𝑝]) within a custom bitvector encoding. We derive a precise condition for guaranteed monotonicity, proving that non-monotonicity can only occur when 𝑝 ≤ ⌊log2 (𝑛 − 1) − 2⌋. We also derive a formula for the maximum magnitude of error when non-monotonicity can occur. Our results provide hardware architects with provably correct design parameters to eliminate such anomalies, ensuring greater numerical stability.

Best Poster Finalist (BP): no
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