Fix test failure from #40435

[antonio-rojas]

Fixes

File "sage-src/src/sage/matrix/matrix_gfpn_dense.pyx", line 693, in sage.matrix.matrix_gfpn_dense.Matrix_gfpn_dense.copy_from_unsafe
Failed example:
    M = MatrixSpace(K, 3, 4, implementation=Matrix_gfpn_dense)(range(12))
Exception raised:
    Traceback (most recent call last):
      File "/usr/lib/python3.13/site-packages/sage/doctest/forker.py", line 733, in _run
        self.compile_and_execute(example, compiler, test.globs)
        ~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
      File "/usr/lib/python3.13/site-packages/sage/doctest/forker.py", line 1157, in compile_and_execute
        exec(compiled, globs)
        ~~~~^^^^^^^^^^^^^^^^^
      File "<doctest sage.matrix.matrix_gfpn_dense.Matrix_gfpn_dense.copy_from_unsafe[1]>", line 1, in <module>
        M = MatrixSpace(K, Integer(3), Integer(4), implementation=Matrix_gfpn_dense)(range(Integer(12)))
                                                                  ^^^^^^^^^^^^^^^^^
    NameError: name 'Matrix_gfpn_dense' is not defined

This isn't detected by CI as it depends on the optional meataxe package

[xcaruso]

Thanks!

[xcaruso]

On my computer:

sage: from sage.matrix.matrix_gfpn_dense import Matrix_gfpn_dense
Traceback (most recent call last)
...
ModuleNotFoundError: No module named 'sage.matrix.matrix_gfpn_dense'

I think it's because it's a pyx file.

[antonio-rojas]

On my computer:

sage: from sage.matrix.matrix_gfpn_dense import Matrix_gfpn_dense
Traceback (most recent call last)
...
ModuleNotFoundError: No module named 'sage.matrix.matrix_gfpn_dense'

I think it's because it's a pyx file.

You don't have the extension compiled. It's optional and you need to explicitly compile it (sage -i meataxe)

[github-actions]

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[xcaruso]

Suggested change

	sage: from sage.matrix.matrix_gfpn_dense import Matrix_gfpn_dense
	sage: K.<z> = GF(59)
	sage: M = MatrixSpace(K, 3, 4, implementation=Matrix_gfpn_dense)(range(12))
	sage: K.<z> = GF(25)
	sage: M = MatrixSpace(K, 3, 4, implementation='meataxe')(range(12)) # optional - meataxe, needs sage.rings.finite_rings

[antonio-rojas]

This doesn't work for me, it gives a AssertionError. Also, the optional - meataxe directive is not necessary as it's already present at the top of the file

[xcaruso]

You don't have the extension compiled. It's optional and you need to explicitly compile it (sage -i meataxe)

Ok. Then it looks fine.