Cached generator matrices and parity check matrices should be immutable

[johanrosenkilde]

In all linear code classes, constructed generator matrices and parity check matrices are cached for efficiency. However, they are often not immutable, leading to incorrect behaviour if the user inadvertently changes them.

sage: C = codes.GeneralizedReedSolomonCode(GF(7).list(), 3)
sage: C.generator_matrix()[0,0] = 0
sage: C.generator_matrix().row(0) in C
False

All such cached matrices should be made immutable by G.set_immutable(True).

Depends on #21328

CC: @sagetrac-dlucas

Component: coding theory

Keywords: linear code, rd3

Author: Clément Pernet

Branch/Commit: ac0e4f9

Reviewer: David Lucas

Issue created by migration from https://trac.sagemath.org/ticket/21159

[ClementPernet]

Branch: u/cpernet/immutable_generator_matrix

[ClementPernet]

comment:3

I processed all code classes with the following update:

• add some @cached_method decorator when it was missing to a generator_matrix or a parity_check method
• systematically set immutable these cached matrices
  Branch attached ready for review.

[ClementPernet]

Commit: d07341b

[ClementPernet]

Author: Clément Pernet

[sagetrac-git]

Changed commit from d07341b to 8409076

[sagetrac-git]

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

8409076

fix mistake: make the matrix immutable, not the tuple

[sagetrac-dlucas]

comment:7

Tests pass and doc builds, I agree with your changes, setting to positive review.

David

[sagetrac-dlucas]

Reviewer: David Lucas

[sagetrac-dlucas]

Changed keywords from linear code to linear code, rd3

[sagetrac-dlucas]

Changed branch from u/cpernet/immutable_generator_matrix to u/dlucas/immutable_generator_matrix

[sagetrac-dlucas]

Changed commit from 8409076 to ac0e4f9

[sagetrac-dlucas]

comment:9

Well, reopenig this ticket to include parity check codes (#21328) in it.
Waiting for review...

David

---

New commits:

b77de0f	Added new file that introduces the new parity-check code class. Initializes code class, generator matrix encoder class, straightforward encoder class and minimum distance method.
0b0d2f8	Correcting mistakes. Two errors are still waiting for correction: ParityCheckCodeStraightforwardEncoder.unencode_nocheck and ParityCheckCodeGeneratorMatrixEncoder.__init__
62abcd7	Fixed merge conflict.
1aa4b4e	Fixed doctests. Shorter output. Generator matrix encoder inherits from the generic one. Fixed encoders. Cleaned the code.
64ee227	Merged ticket #21328 in
ac0e4f9	Immutable generator matrix for parity codes

[sagetrac-dlucas]

Dependencies: #21328

[ClementPernet]

comment:11

Positive review to the merge and last commit by dlucas.

[vbraun]

Changed branch from u/dlucas/immutable_generator_matrix to ac0e4f9