[with patch positive review] kernels of integer matrices

[jhpalmieri]

sage: id = matrix(ZZ, 2, 2, [[1, 0], [0, 1]]) 
sage: id.left_kernel()
Traceback
...
TypeError: Argument K (= Integer Ring) must be a field.

On the other hand, id.right_kernel() and id.kernel() both work, and id.kernel() actually computes the left kernel. Note also that the documentation for both left_kernel and right_kernel says that the answer will be a vector space, not a module over the integers; this should be fixed, too.

Component: linear algebra

Keywords: matrix, kernel

Issue created by migration from https://trac.sagemath.org/ticket/5001

[williamstein]

Attachment: trac_5001.patch.gz

[jhpalmieri]

comment:2

Looks good, all tests passed. A few comments: the documentation still says "vector space" when computing the kernel of an integer matrix, but I can live with that. Perhaps more seriously, if you don't apply patch #5089, then computing the kernel (or left_kernel or right_kernel) of a sparse integer matrix leads to a segmentation fault. Does this need to be investigated further?

[sagetrac-mabshoff]

comment:3

Since #5089 is being merged I am changing this to a positive review. The documentation issue about vector spaces vs. modules should be addressed via a followup ticket.

Cheers,

Michael

[sagetrac-mabshoff]

comment:4

Merged in Sage 3.3.alpha2

Cheers,

Michael