Sparse integer matrices.

AUTHORS:

  • William Stein (2007-02-21)
  • Soroosh Yazdani (2007-02-21)
class sage.matrix.matrix_integer_sparse.Matrix_integer_sparse

Bases: sage.matrix.matrix_sparse.Matrix_sparse

Create a sparse matrix over the integers.

INPUT:

  • parent – a matrix space
  • entries – can be one of the following:
    • a Python dictionary whose items have the form (i, j): x, where 0 <= i < nrows, 0 <= j < ncols, and x is coercible to an integer. The i,j entry of self is set to x. The x‘s can be 0.
    • Alternatively, entries can be a list of all the entries of the sparse matrix, read row-by-row from top to bottom (so they would be mostly 0).
  • copy – ignored
  • coerce – ignored
elementary_divisors(algorithm='pari')

Return the elementary divisors of self, in order.

The elementary divisors are the invariants of the finite abelian group that is the cokernel of left multiplication by this matrix. They are ordered in reverse by divisibility.

INPUT:

  • self – matrix
  • algorithm – (default: ‘pari’)
    • ‘pari’: works robustly, but is slower.
    • ‘linbox’ – use linbox (currently off, broken)

OUTPUT:

list of integers

EXAMPLES:

sage: matrix(3, range(9),sparse=True).elementary_divisors()
[1, 3, 0]
sage: M = matrix(ZZ, 3, [1,5,7, 3,6,9, 0,1,2], sparse=True)
sage: M.elementary_divisors()
[1, 1, 6]

This returns a copy, which is safe to change:

sage: edivs = M.elementary_divisors()
sage: edivs.pop()
6
sage: M.elementary_divisors()
[1, 1, 6]

See also

smith_form()

hermite_form(algorithm='default', cutoff=0, **kwds)

Return the echelon form of self.

Note

This row reduction does not use division if the matrix is not over a field (e.g., if the matrix is over the integers). If you want to calculate the echelon form using division, then use rref(), which assumes that the matrix entries are in a field (specifically, the field of fractions of the base ring of the matrix).

INPUT:

  • algorithm – string. Which algorithm to use. Choices are
    • 'default': Let Sage choose an algorithm (default).
    • 'classical': Gauss elimination.
    • 'strassen': use a Strassen divide and conquer algorithm (if available)
  • cutoff – integer. Only used if the Strassen algorithm is selected.
  • transformation – boolean. Whether to also return the transformation matrix. Some matrix backends do not provide this information, in which case this option is ignored.

OUTPUT:

The reduced row echelon form of self, as an immutable matrix. Note that self is not changed by this command. Use echelonize() to change self in place.

If the optional parameter transformation=True is specified, the output consists of a pair \((E,T)\) of matrices where \(E\) is the echelon form of self and \(T\) is the transformation matrix.

EXAMPLES:

sage: MS = MatrixSpace(GF(19),2,3)
sage: C = MS.matrix([1,2,3,4,5,6])
sage: C.rank()
2
sage: C.nullity()
0
sage: C.echelon_form()
[ 1  0 18]
[ 0  1  2]

The matrix library used for \(\ZZ/p\)-matrices does not return the transformation matrix, so the transformation option is ignored:

sage: C.echelon_form(transformation=True)
[ 1  0 18]
[ 0  1  2]

sage: D = matrix(ZZ, 2, 3, [1,2,3,4,5,6])
sage: D.echelon_form(transformation=True)
(
[1 2 3]  [ 1  0]
[0 3 6], [ 4 -1]
)
sage: E, T = D.echelon_form(transformation=True)
sage: T*D == E
True
rational_reconstruction(N)

Use rational reconstruction to lift self to a matrix over the rational numbers (if possible), where we view self as a matrix modulo N.

EXAMPLES:

sage: A = matrix(ZZ, 3, 4, [(1/3)%500, 2, 3, (-4)%500, 7, 2, 2, 3, 4, 3, 4, (5/7)%500], sparse=True)
sage: A.rational_reconstruction(500)
[1/3   2   3  -4]
[  7   2   2   3]
[  4   3   4 5/7]
smith_form()

Returns matrices S, U, and V such that S = U*self*V, and S is in Smith normal form. Thus S is diagonal with diagonal entries the ordered elementary divisors of S.

This version is for sparse matrices and simply makes the matrix dense and calls the version for dense integer matrices.

Warning

The elementary_divisors function, which returns the diagonal entries of S, is VASTLY faster than this function.

The elementary divisors are the invariants of the finite abelian group that is the cokernel of this matrix. They are ordered in reverse by divisibility.

EXAMPLES:

sage: A = MatrixSpace(IntegerRing(), 3, sparse=True)(range(9))
sage: D, U, V = A.smith_form()
sage: D
[1 0 0]
[0 3 0]
[0 0 0]
sage: U
[ 0  1  0]
[ 0 -1  1]
[-1  2 -1]
sage: V
[-1  4  1]
[ 1 -3 -2]
[ 0  0  1]
sage: U*A*V
[1 0 0]
[0 3 0]
[0 0 0]

It also makes sense for nonsquare matrices:

sage: A = Matrix(ZZ,3,2,range(6), sparse=True)
sage: D, U, V = A.smith_form()
sage: D
[1 0]
[0 2]
[0 0]
sage: U
[ 0  1  0]
[ 0 -1  1]
[-1  2 -1]
sage: V
[-1  3]
[ 1 -2]
sage: U * A * V
[1 0]
[0 2]
[0 0]

The examples above show that trac ticket #10626 has been implemented.

See also

elementary_divisors()