📚 Description

Added method for block matrix representation of a one-sum node. Issue found with one_sum method in matrix_cmr_sparse.pyx, found as follows:

sage: from sage.matrix.matrix_cmr_sparse import Matrix_cmr_chr_sparse
sage: M3 = Matrix_cmr_chr_sparse.one_sum([[1, 0], [-1, 1]], [[1, 1], [-1, 0]], [[1, 0], [0,1]]
....:
....: ....: ); M3
[ 1 0| 0 0| 0 0]
[-1 1| 0 0| 0 0]
[-----+-----+-----]
[ 0 0| 1 1| 0 0]
[ 0 0|-1 0| 0 0]
[-----+-----+-----]
[ 0 0| 0 0| 1 0]
[ 0 0| 0 0| 0 1]
sage: result, certificate = M3.is_totally_unimodular(certificate=True); certificate
OneSumNode with 4 children
sage: certificate.block_diagonal_repr()
[ 1 0| 0 0| 0| 0]
[-1 1| 0 0| 0| 0]
[-----+-----+--+--]
[ 0 0| 1 1| 0| 0]
[ 0 0|-1 0| 0| 0]
[-----+-----+--+--]
[ 0 0| 0 0| 1| 0]
[-----+-----+--+--]
[ 0 0| 0 0| 0| 1]
sage: type(certificate)
<class 'sage.matrix.seymour_decomposition.OneSumNode'>
sage: certificate.block_diagonal_repr()

OverflowError Traceback (most recent call last)
Cell In [7], line 1
----> 1 certificate.block_diagonal_repr()

File ~/sage/worktree-cmr/src/sage/matrix/seymour_decomposition.pyx:252, in sage.matrix.seymour_decomposition.OneSumNode.block_diagonal_repr()
250 [ 0 0| 0 0| 0| 1]
251 """
--> 252 return Matrix_cmr_chr_sparse.one_sum(*self.get_children_matrices())
253
254

File ~/sage/worktree-cmr/src/sage/matrix/seymour_decomposition.pyx:199, in genexpr()
197 if self._children() is None:
198 raise ValueError('Node has no children')
--> 199 return tuple(ch.matrix() for ch in self._children())
200
201

File ~/sage/worktree-cmr/src/sage/matrix/seymour_decomposition.pyx:199, in genexpr()
197 if self._children() is None:
198 raise ValueError('Node has no children')
--> 199 return tuple(ch.matrix() for ch in self._children())
200
201

File ~/sage/worktree-cmr/src/sage/misc/cachefunc.pyx:2301, in sage.misc.cachefunc.CachedMethodCallerNoArgs.call()
2299 if self.cache is None:
2300 f = self.f
-> 2301 self.cache = f(self._instance)
2302 return self.cache
2303

File ~/sage/worktree-cmr/src/sage/matrix/seymour_decomposition.pyx:59, in sage.matrix.seymour_decomposition.DecompositionNode.matrix()
57 if mat == NULL:
58 return None
---> 59 ms = MatrixSpace(ZZ, mat.numRows, mat.numColumns, sparse=True)
60 result = Matrix_cmr_chr_sparse.new(Matrix_cmr_chr_sparse, ms)
61 result._mat = mat

File ~/sage/worktree-cmr/src/sage/misc/classcall_metaclass.pyx:320, in sage.misc.classcall_metaclass.ClasscallMetaclass.call()
318 """
319 if cls.classcall is not None:
--> 320 return cls.classcall(cls, *args, **kwds)
321 else:
322 # Fast version of type.call(cls, *args, **kwds)

File ~/sage/worktree-cmr/src/sage/matrix/matrix_space.py:587, in MatrixSpace.classcall(cls, base_ring, nrows, ncols, sparse, implementation, **kwds)
585 raise ArithmeticError("ncols must be nonnegative")
586 if nrows > sys.maxsize or ncols > sys.maxsize:
--> 587 raise OverflowError("number of rows and columns may be at most %s" % sys.maxsize)
589 matrix_cls = get_matrix_class(base_ring, nrows, ncols, sparse, implementation)
590 return super().classcall(cls, base_ring, nrows,
591 ncols, sparse, matrix_cls, **kwds)

OverflowError: number of rows and columns may be at most 9223372036854775807

📝 Checklist

• [x ] The title is concise, informative, and self-explanatory.
• The description explains in detail what this PR is about.
• I have linked a relevant issue or discussion.
• I have created tests covering the changes.
• I have updated the documentation accordingly.

⌛ Dependencies