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AutoGraph: Imperative-style Coding with Graph-based Performance

Dan Moldovan
James Decker
Fei Wang
Andrew Johnson
Brian Lee
Tiark Rompf
Alexander B Wiltschko
SysML (2019)


Traditionally there has been a perceived trade-off between machine learning code that is easy to write and machine learning code that fast, scalable, or easy to distribute, with platforms like TensorFlow, Theano, PyTorch, and Autograd inhabiting different points along this tradeoff curve. PyTorch and Autograd offer the coding benefits of imperative programming style and accept the computational tradeoff of interpretive overhead. TensorFlow and Theano give the benefit of whole-program optimization based on defined computation graphs, with the trade-off of potentially cumbersome graph-based semantics and associated developer overhead, which become especially apparent for more complex model types that depend on control flow operators. We propose to capture the benefits of both paradigms, using imperative programming style while enabling high performance program optimization, by using staged programming via source code transformation to essentially compile native Python into a lower-level IR like TensorFlow graphs. A key insight is to delay all type-dependent decisions until runtime, via dynamic dispatch. We instantiate these principles in AutoGraph, a piece of software that improves the programming experience of the TensorFlow machine learning library, and demonstrate the strong usability improvements with no loss in performance compared to native TensorFlow graphs.\end{abstract}