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Update pxgcd.rs

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This commit is contained in:
goldenMetteyya 2019-03-07 16:16:28 +03:00
parent 9750e2cfbe
commit d0b7f4620e
1 changed files with 10 additions and 10 deletions
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20
src/algorithms/pxgcd.rs
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@ -1,12 +1,6 @@
// Partial Euclidean algorithm.
// Lehmer's version for computing GCD
// Flint-2.4.1 Book
// This function is an implementation of Lehmer extended GCD with early termination,
// as used in the qfb module. It terminates early when remainders fall below the specified bound.
// The initial values r1 and r2 are treated as successive remainders in the Euclidean algorithm
// and are replaced with the last two remainders computed. The values co1 and co2 are the last two
// cofactors and satisfy the identity co2*r1 - co1*r2 == +/- r2_orig upon termination, where
// r2_orig is the starting value of r2 supplied, and r1 and r2 are the final values.
// Ported from Flint-2.4.1
use crate::bigint::{Sign, BigInt};
@ -20,6 +14,12 @@ use bigint::ToBigInt;
//This function is an implementation of Lehmer extended GCD with early termination.
//It terminates early when remainders fall below the specified bound.
// The initial values r1 and r2 are treated as successive remainders in the Euclidean algorithm
// and are replaced with the last two remainders computed. The values co1 and co2 are the last two
// cofactors and satisfy the identity co2*r1 - co1*r2 == +/- r2_orig upon termination, where
// r2_orig is the starting value of r2 supplied, and r1 and r2 are the final values.
pub fn partial_extended_gcd(
r2_in: Cow<BigInt>,
r1_in: Cow<BigInt>,
@ -231,9 +231,9 @@ pub fn partial_extended_gcd(
// make sure R2 is positive
if r2.sign() == Sign::Minus {
co1.sign = co1.sign.neg();
co2.sign = co2.sign.neg();
r2.sign = r2.sign.neg();
co1.negate_sign();
co2.negate_sign();
r2.negate_sign();
}
//return back