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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 = {7451904, 371210988, 148215588, 260679744, 86537616}

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

o2 = (372, | 17  -11 -20 -17 -13 |)
           | -12 -1  -9  -22 -4  |
           | 4   3   -21 46  13  |
           | 13  8   24  4   1   |
           | 4   -24 4   5   -7  |

o2 : Sequence
i3 : matrix{s} * z

o3 = | 0 0 0 0 372 |

              1        5
o3 : Matrix ZZ  <--- ZZ

See also

Ways to use gcdLLL :