Re: [boost] New library proposal: Autodiff

-----Original Message----- From: Boost On Behalf Of Matt Pulver via Boost Sent: Tuesday, December 18, 2018 5:38 PM

Hello,

An automatic differentiation https://en.wikipedia.org/wiki/Automatic_differentiation C++ library - Autodiff - is released under the Boost License and is proposed for inclusion into Boost:

- Github: https://github.com/pulver/autodiff - Boost Library Incubator: http://blincubator.com/bi_library/autodiff-2/?gform_post_id=1716

Features:

- Instances of autodiff variables satisfy Boost's Conceptual Requirements for Real Number Types https://www.boost.org/doc/libs/1_69_0/libs/math/doc/html/math_toolkit/real_c.... In fact the class and function template definitions are based upon the tables in this page. - No use of dynamic memory. The only member variable is a std::array<>. - Consistent with Boost's type promotion templates. When adding/multiplying/etc. variables of differing dimension number and sizes, the resulting data type is calculated at compile-time. - Single header-only file. - Intuitive and minimal API.

Requirements:

- C++17 compiler that supports constexpr if statements. There are a fair amount of calculations done at compile-time which would require messy SFINAE hacks to make this C++14-compatible.

Todo:

- A github build matrix that also includes clang and MSVC. - Additional documentation, including the mathematics.

Feedback and endorsements for Boost Library inclusion are welcome and requested.

1) What exactly is mean by "Standard Library Support Requirements"? Do my types have to work with the actual Standard library functions (e.g. via implicit conversion to double) or does there have to be a function with the same name that can be found via ADL? 2) Any plan to support types, where the result of a math operation might not be the same as the operands? 3) Regarding the language standard: Don't use c++17 just for the sake of it, or because it simplifies a few lines of code. But if (contrary to Peter Dimov's statement) it actually lets you avoid lots of template machinery It probably also reduces compile times and I for one would be very happy to see a library that prioritizes implementation simplicity and compile times over support for outdated standards and compilers. Best Mike

Best regards, Matt

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