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We also deprecate the outdated and unused global function linear_program, which directly uses cvxopt.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

[mkoeppe]

Description changed:

--- 
+++ 
@@ -1,5 +1,5 @@
 `sage.numerical.sdp` and the backends `cvxopt_backend` and `cvxopt_sdp_backend` are underdeveloped and unmaintained to the point of being unusable. `SemidefiniteProgram`, introduced over 5 years ago, is not used anywhere in the Sage library.
 
-Given the brittle build system of `cvxopt` (#31905, #32087, and of its dependency `suitesparse` (#30478), we will be better off making them optional instead of standard packages.
+Given the brittle build system of `cvxopt` (#31905, #32087), and of its dependency `suitesparse` (#30478), we will be better off making them optional instead of standard packages.
 
 

[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

[mkoeppe]

Description changed:

--- 
+++ 
@@ -2,4 +2,5 @@
 
 Given the brittle build system of `cvxopt` (#31905, #32087), and of its dependency `suitesparse` (#30478), we will be better off making them optional instead of standard packages.
 
+We also deprecate the outdated and unused global function `linear_program`, which directly uses `cvxopt`.
 

[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.