"""
Functions for changing the base ring of matrices quickly.
"""
from matrix_space import MatrixSpace
from matrix_real_double_dense cimport Matrix_real_double_dense
from matrix_integer_dense cimport Matrix_integer_dense
from sage.rings.real_double import RDF
include "../ext/cdefs.pxi"
include "../ext/interrupt.pxi"
def integer_to_real_double_dense(Matrix_integer_dense A):
"""
Fast conversion of a matrix over the integers to a matrix with
real double entries.
INPUT:
A -- a dense matrix over the integers
OUTPUT:
-- a dense real double matrix
EXAMPLES:
sage: a = matrix(ZZ,2,3,[-2,-5,3,4,8,1030339830489349908])
sage: a.change_ring(RDF)
[ -2.0 -5.0 3.0]
[ 4.0 8.0 1.03033983049e+18]
sage: import sage.matrix.change_ring
sage: sage.matrix.change_ring.integer_to_real_double_dense(a)
[ -2.0 -5.0 3.0]
[ 4.0 8.0 1.03033983049e+18]
"""
cdef Py_ssize_t i, j
cdef Matrix_real_double_dense M
S = MatrixSpace(RDF, A._nrows, A._ncols, sparse=False)
M = Matrix_real_double_dense.__new__(Matrix_real_double_dense,
S, None, None, None)
for i from 0 <= i < A._nrows:
for j from 0 <= j < A._ncols:
M.set_unsafe_double(i, j, mpz_get_d(A._matrix[i][j]))
return M
