[eigen] eigen and API stability

[Nicolas Limare <nicolas.limare@xxxxxxxxxxxxxxxxxx>]

Hi,

I am working with/on IPOL, a research journal where software is
reviewed and published[1]. IPOL has software guidelines with, among
other things, a list of libraries the journal authors are allowed to
use in the software they send to the journal. We want software
published in IPOL to be usable as long as possible, on various
environments, so we only accept portable libraries with a stable API.

We are discussing the opportunity to add Eigen to this list of allowed
libraries. Eigen seems quite portable, as stated in the "Compiler
Support" section of the website main page[3]. I see no statement about
the OS, so I suppose Eigen is OS-agnostic.

But I would like to know more aboit the API stability. Specifically, I
wonder how long will a code written with Eigen 3.2 be usable with the
latest maintained version of Eigen.

Is there a project policy regarding this API stability? Do you require
that any code written for Eigen 3.n is usable without changes with
Eigen 3.m for any m>=n? I understand there are some unit tests, but
are are all tests written for 3.n versions kept unchanged for future
3.m versions?

What is the current development plan for Eigen, how long do you expect
to stay on the 3.x branch (which, I suppose, implies a major API version)?
And if/when Eigen moves to a 4.x branch, will the 3.x branch still be
maintained, especially fixed to be compilable with the latest compilers?

For example, I like this statement by GSL people: "GSL is a mature
library with a stable API. The main emphasis is on ensuring the
stability of the existing functions, tidying up and fixing any bugs
that are reported."[4] If the same thing can not be written for Eigen
(or can it?), which API policy statement could be written instead?

All the best,

[1]http://www.ipol.im
[2]https://tools.ipol.im/wiki/ref/software_guidelines/#external-libraries
[3]http://eigen.tuxfamily.org/#Compiler_support
[4]http://www.gnu.org/software/gsl/#development

-- 
Nicolas LIMARE - CMLA - ENS Cachan         http://limare.perso.math.cnrs.fr/
IPOL journal                                             http://www.ipol.im/
-> image processing, reproducible research, open science

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