Sparse integer matrices

AUTHORS:

• William Stein (2007-02-21)

• Soroosh Yazdani (2007-02-21)

class sage.matrix.matrix_integer_sparse.Matrix_integer_sparse

Bases: Matrix_sparse

Create a sparse matrix over the integers.

INPUT:

• parent – a matrix space over ZZ

• entries – see matrix()

• copy – ignored (for backwards compatibility)

• coerce – if False, assume without checking that the entries are of type Integer

charpoly(var='x', algorithm=None)

Return the characteristic polynomial of this matrix.

INPUT:

• var – (default: 'x') the name of the variable of the polynomial

• algorithm – (default: None) one of None, 'linbox', or an algorithm accepted by sage.matrix.matrix_sparse.Matrix_sparse.charpoly()

EXAMPLES:

sage: M = MatrixSpace(ZZ, 4, sparse=True)
sage: m = M()
sage: m[0,0] = m[1,2] = m[2,3] = m[3,3] = 1
sage: m[0,2] = m[1,3] = m[2,0] = m[3,0] = -3
sage: m[1,1] = 2
sage: m
[ 1  0 -3  0]
[ 0  2  1 -3]
[-3  0  0  1]
[-3  0  0  1]
sage: m.charpoly()
x^4 - 4*x^3 - 4*x^2 + 16*x

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)

alias of echelon_form().

minpoly(var='x', algorithm=None)

Return the minimal polynomial of this matrix.

INPUT:

• var – (default: 'x') the name of the variable of the polynomial

• algorithm – (default: None) one of None, 'linbox', or an algorithm accepted by sage.matrix.matrix_sparse.Matrix_sparse.minpoly()

EXAMPLES:

sage: M = MatrixSpace(ZZ, 4, sparse=True)
sage: m = M({(0, 0):2, (1, 1):1, (2, 1):-8, (2, 2):2, (2, 3):-1, (3, 3):1})
sage: m
[ 2  0  0  0]
[ 0  1  0  0]
[ 0 -8  2 -1]
[ 0  0  0  1]
sage: m.minpoly()
x^2 - 3*x + 2

rank(algorithm=None)

Compute the rank of this matrix.

INPUT:

• algorithm – (optional) one of None, 'linbox' or 'generic'

EXAMPLES:

sage: M = MatrixSpace(ZZ, 3, 2, sparse=True)
sage: m = M([1, 0, 2, 3, -1, 0])
sage: m.rank()
2

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(transformation=True, integral=None)

Return the smith normal form of this matrix, that is the diagonal matrix $S$ with diagonal entries the ordered elementary divisors of this matrix.

INPUT:

• transformation – boolean (default: True); whether to return the transformation matrices $U$ and $V$ such that $S=U\cdot self\cdot V$

• integral – a subring of the base ring or True (default: None); ignored for matrices with integer entries

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

Note

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  2 -1]
[ 0 -1  1]
[ 1 -2  1]
sage: V
[ 0  0  1]
[-1  2 -2]
[ 1 -1  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  2 -1]
[ 0 -1  1]
[ 1 -2  1]
sage: V
[-1  1]
[ 1  0]
sage: U * A * V
[1 0]
[0 2]
[0 0]

The examples above show that Issue #10626 has been implemented.

See also

elementary_divisors()