Differentiable programming is a programming paradigm in which the programs can be differentiated throughout, usually via automatic differentiation. This allows for gradient based optimization of parameters in the program, often via gradient descent. Differentiable programming has found use in a wide variety of areas, particularly scientific computing and artificial intelligence.
Most differentiable programming frameworks work by constructing a graph containing the control flow and data structures in the program. Earlier attempts generally fall into two groups:
- Static, compiled graph based approaches such as TensorFlow, Theano, and MXNet. They tend to allow for good compiler optimization and easier scaling to large systems, but their static nature limits interactivity and the types of programs that can be created easily (e.g. those involving loops or recursion), as well as making it harder for users to reason effectively about their programs.
- Operator overloading, dynamic graph based approaches such as PyTorch and AutoGrad. Their dynamic and interactive nature lets most programs be written and reasoned about more easily. However, they lead to interpreter overhead (particularly when composing many small operations), poorer scalability, and struggle to gain benefit from compiler optimization.
Both of these early approaches are only able to differentiate code written in a suitable manner for the framework, limiting their interoperability with other programs.
More recent packages in the Julia programming language — Zygote, the Swift programming language — Swift for TensorFlow, and a programming language called Myia, resolve the issues that earlier attempts faced by treating the language's syntax as the graph. The intermediate representation of arbitrary code can then be differentiated directly, optimized, and compiled.
- TensorFlow 1 uses the static graph approach, whereas TensorFlow 2 uses the dynamic graph approach by default.
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