Saturation over ZZ

sage.matrix.matrix_integer_dense_saturation.index_in_saturation(A, proof=True)

The index of A in its saturation.

INPUT:

• A – matrix over \(\ZZ\)
• proof – boolean (True or False)

OUTPUT:

An integer

EXAMPLES:

sage: from sage.matrix.matrix_integer_dense_saturation import index_in_saturation
sage: A = matrix(ZZ, 2, 2, [3,2,3,4]); B = matrix(ZZ, 2,3,[1,2,3,4,5,6]); C = A*B; C
[11 16 21]
[19 26 33]
sage: index_in_saturation(C)
18
sage: W = C.row_space()
sage: S = W.saturation()
sage: W.index_in(S)
18

For any zero matrix the index in its saturation is 1 (see trac ticket #13034):

sage: m = matrix(ZZ, 3)
sage: m
[0 0 0]
[0 0 0]
[0 0 0]
sage: m.index_in_saturation()
1
sage: m = matrix(ZZ, 2, 3)
sage: m
[0 0 0]
[0 0 0]
sage: m.index_in_saturation()
1

sage.matrix.matrix_integer_dense_saturation.p_saturation(A, p, proof=True)

INPUT:

• A – a matrix over ZZ
• p – a prime
• proof – bool (default: True)

OUTPUT:

The p-saturation of the matrix A, i.e., a new matrix in Hermite form whose row span a ZZ-module that is p-saturated.

EXAMPLES:

sage: from sage.matrix.matrix_integer_dense_saturation import p_saturation
sage: A = matrix(ZZ, 2, 2, [3,2,3,4]); B = matrix(ZZ, 2,3,[1,2,3,4,5,6])
sage: A.det()
6
sage: C = A*B; C
[11 16 21]
[19 26 33]
sage: C2 = p_saturation(C, 2); C2
[ 1  8 15]
[ 0  9 18]
sage: C2.index_in_saturation()
9
sage: C3 = p_saturation(C, 3); C3
[ 1  0 -1]
[ 0  2  4]
sage: C3.index_in_saturation()
2

sage.matrix.matrix_integer_dense_saturation.random_sublist_of_size(k, n)

INPUT:

• k – an integer
• n – an integer

OUTPUT:

a randomly chosen sublist of range(k) of size n.

EXAMPLES:

sage: import sage.matrix.matrix_integer_dense_saturation as s
sage: s.random_sublist_of_size(10,3)
[0, 1, 5]
sage: s.random_sublist_of_size(10,7)
[0, 1, 3, 4, 5, 7, 8]

sage.matrix.matrix_integer_dense_saturation.saturation(A, proof=True, p=0, max_dets=5)

Compute a saturation matrix of A.

INPUT:

• A – a matrix over ZZ
• proof – bool (default: True)
• p – int (default: 0); if not 0 only guarantees that output is p-saturated
• max_dets – int (default: 4) max number of dets of submatrices to compute.

OUTPUT:

matrix – saturation of the matrix A.

EXAMPLES:

sage: from sage.matrix.matrix_integer_dense_saturation import saturation
sage: A = matrix(ZZ, 2, 2, [3,2,3,4]); B = matrix(ZZ, 2,3,[1,2,3,4,5,6]); C = A*B
sage: C
[11 16 21]
[19 26 33]
sage: C.index_in_saturation()
18
sage: S = saturation(C); S
[11 16 21]
[-2 -3 -4]
sage: S.index_in_saturation()
1
sage: saturation(C, proof=False)
[11 16 21]
[-2 -3 -4]
sage: saturation(C, p=2)
[11 16 21]
[-2 -3 -4]
sage: saturation(C, p=2, max_dets=1)
[11 16 21]
[-2 -3 -4]

sage.matrix.matrix_integer_dense_saturation.solve_system_with_difficult_last_row(B, A)

Solve the matrix equation B*Z = A when the last row of \(B\) contains huge entries.

INPUT:

• B – a square n x n nonsingular matrix with painful big bottom row.
• A – an n x k matrix.

OUTPUT:

the unique solution to B*Z = A.

EXAMPLES:

sage: from sage.matrix.matrix_integer_dense_saturation import solve_system_with_difficult_last_row
sage: B = matrix(ZZ, 3, [1,2,3, 3,-1,2,939239082,39202803080,2939028038402834]); A = matrix(ZZ,3,2,[1,2,4,3,-1,0])
sage: X = solve_system_with_difficult_last_row(B, A); X
[  290668794698843/226075992027744         468068726971/409557956572]
[-226078357385539/1582531944194208       1228691305937/2866905696004]
[      2365357795/1582531944194208           -17436221/2866905696004]
sage: B*X == A
True