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Transformers, parallel computation, and logarithmic depth
Proceedings of the 41st International Conference on Machine Learning, PMLR 235:43276-43327, 2024.
Abstract
We show that a constant number of self-attention layers can efficiently simulate—and be simulated by—a constant number of communication rounds of Massively Parallel Computation. As a consequence, we show that logarithmic-depth is sufficient for transformers to solve basic computational tasks that cannot be efficiently solved by several other neural sequence models and sub-quadratic transformer approximations. We thus establish parallelism as a key distinguishing property of transformers.