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LLLBases > gcdLLL

gcdLLL -- compute the gcd of integers, and small multipliers

Synopsis

Description

This function is provided by the package LLLBases.

The first n-1 columns of the matrix z form a basis of the kernel of the n integers of the list s, and the dot product of the last column of z and s is the gcd g.

The method used is described in the paper:

Havas, Majewski, Matthews, Extended GCD and Hermite Normal Form Algorithms via Lattice Basis Reduction, Experimental Mathematics 7:2 p. 125 (1998).

For an example,

i1 : s = apply(5,i->372*(random 1000000))

o1 = {284319228, 136785516, 239006652, 327463416, 116372016}

o1 : List
i2 : (g,z) = gcdLLL s

o2 = (372, | -4 25  22  1   -3  |)
           | 7  21  -16 31  17  |
           | -5 10  -40 -6  3   |
           | 1  -36 15  3   -1  |
           | 9  -5  5   -35 -16 |

o2 : Sequence
i3 : matrix{s} * z

o3 = | 0 0 0 0 372 |

              1        5
o3 : Matrix ZZ  <--- ZZ

See also

Ways to use gcdLLL :