configure: Add option --disable-cvxopt

[mkoeppe]

Given the brittle build system of cvxopt (#31905, #32087), and of its dependency suitesparse (#30478), we should give users a recourse when the installation fails.

cvxopt provides our only backend for SemidefiniteProgram, introduced over 5 years ago. Although not yet used anywhere in the Sage library, it provides important functionality for a number of Sage user, e.g.
it's used in https://github.com/bachirelkhadir/sdp_solvers_experiments which is needed for
demonstration of https://epubs.siam.org/doi/pdf/10.1137/19M1287584 in
https://github.com/bachirelkhadir/Convex-Quaternary-Quartics-Are-Sum-of-Squares/blob/master/optimal_constant_generalized_cs_deg_8_a4.pdf

Hence, we keep cvxopt as a standard package, but make it disablable.

Marking doctests that depend on cvxopt with # optional - cvxopt is also preparation for modularization. Thanks to the dummy backend MatrixSDPBackend, the modeling side of the interface can still be doctested even if cvxopt is not installed.

We also deprecate the outdated and unused global function linear_program, which directly uses cvxopt.

CC: @dimpase @tscrim @orlitzky

Component: packages: standard

Author: Matthias Koeppe

Branch/Commit: 2ab2f15

Reviewer: Dima Pasechnik

Issue created by migration from https://trac.sagemath.org/ticket/32226

[mkoeppe]

Branch: u/mkoeppe/downgrade_suitesparse__cvxopt_to__optional_

[mkoeppe]

Commit: 83e309a

[mkoeppe]

New commits:

83e309a

build/pkgs/{cvxopt,suitesparse}/type: Change to optional

[mkoeppe]

Author: Matthias Koeppe

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

f77a3f8

src/doc/en/thematic_tutorials/numerical_sage/cvxopt.rst: Mark all tests optional - cvxopt

[sagetrac-git]

Changed commit from 83e309a to f77a3f8

[sagetrac-git]

Changed commit from f77a3f8 to 88c2291

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

88c2291

src/sage/numerical/backends/cvxopt_backend.pyx: Mark all tests # optional - cvxopt

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

c3bf30c	src/sage/numerical/backends/cvxopt_sdp_backend.pyx: Mark all tests # optional - cvxopt
198a681	src/sage/numerical/optimize.py: Deprecate linear_program
9955c1f	src/sage/numerical/sdp.pyx, src/sage/numerical/backends/generic_sdp_backend.pyx: Use MatrixSDPBackend as fall back, mark tests using 'solve' # optional - cvxopt

[sagetrac-git]

Changed commit from 88c2291 to 9955c1f

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

4608b0a

src/setup.cfg.m4: Remove cvxopt

[sagetrac-git]

Changed commit from 9955c1f to 4608b0a

[dimpase]

comment:10

I disagree. Most of Sage functionality is not used by sagelib, it's absolutely not a reason to remove it.
Besides, it's the only SDP backend we have at the moment.

A number of publications I have depend on this functionality, and perhaps more.

[mkoeppe]

comment:11

Note that this ticket does not remove cvxopt, it merely makes it optional - same status as cbc and as many other well maintained software that some people use within sage

The problem is that standard packages really need to build on everyone's system, and right now there are unresolved issues (linked in the ticket description).

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

2cde511	configure.ac: Add option --disable-cvxopt
2ab2f15	Revert "build/pkgs/{cvxopt,suitesparse}/type: Change to optional"

[sagetrac-git]

Changed commit from 4608b0a to 2ab2f15

[orlitzky]

comment:15

What's the practical difference between standard-but-optional and plain optional? Is it just the default value of --enable-<pkg> (yes vs no)?

It's a tiny bit annoying to have to remember to --disable-cvxopt when I'm building a branch that doesn't use cvxopt (i.e. pretty much all of them), but I guess that's no different than most packages that disable some things but enable others by default.

[mkoeppe]

comment:16

Replying to @orlitzky:

What's the practical difference between standard-but-optional and plain optional? Is it just the default value of --enable-<pkg> (yes vs no)?

Kind of, but in addition to that, also controls what is packaged up in the source distribution

[dimpase]

Reviewer: Dima Pasechnik

[dimpase]

comment:17

OK, fine by me.

[mkoeppe]

comment:18

Thanks.

[vbraun]

Changed branch from u/mkoeppe/downgrade_suitesparse__cvxopt_to__optional_ to 2ab2f15