Opened 3 years ago

Last modified 3 years ago

#22192 new defect

Insufficient checks when constructing matrix group elements from GAP

Reported by: pbruin Owned by:
Priority: major Milestone: sage-7.6
Component: group theory Keywords:
Cc: Merged in:
Authors: Reviewers:
Report Upstream: N/A Work issues:
Branch: u/pbruin/22192-matrix_group_element_gap (Commits) Commit: 4d71bc26b83572d3e5b7085e4b18fe1d58b2d824
Dependencies: Stopgaps:

Description

In Sage 7.5:

sage: G = GL(2, GF(2))
sage: H = G.subgroup([])
sage: g = G([[0, 1], [1, 0]])
sage: H(g.gap())
[0 1]
[1 0]

This should raise an error since g is not in H.

Change History (2)

comment:1 Changed 3 years ago by pbruin

This is not so straightforward since for e.g. matrix groups over Z, testing membership seems to cause infinite(?) loops in GAP:

sage: a = matrix(ZZ,2,[1,1,0,1])
sage: b = matrix(ZZ,2,[1,0,1,1])
sage: G = MatrixGroup([a])
sage: G(b)  # seems to run forever

We could decide to add checks only over finite base rings.

comment:2 Changed 3 years ago by pbruin

  • Branch set to u/pbruin/22192-matrix_group_element_gap
  • Commit set to 4d71bc26b83572d3e5b7085e4b18fe1d58b2d824

First attempt (does not work due to the above and other reasons)

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