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Add constants for 1/sqrt(a-d) and 1/(a-d)

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This commit is contained in:
Henry de Valence 2017-05-20 16:17:14 -07:00
parent e4913dfc2b
commit 52e51bdb16
1 changed files with 22 additions and 0 deletions
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22
src/constants.rs
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@ -55,6 +55,23 @@ pub const a_minus_d: FieldElement = FieldElement([
8787816, 6275908, 3247719, 18696448, 12055116, ]);
#[cfg(feature="radix_51")]
pub const a_minus_d: FieldElement = FieldElement([1321844580190025, 1785434093556034, 589740348686294, 217950738957124, 809005158844672]);
#[cfg(feature="radix_51")]
pub const invsqrt_a_minus_d: FieldElement = FieldElement([
278908739862762, 821645201101625, 8113234426968, 1777959178193151, 2118520810568447
]);
#[cfg(not(feature="radix_51"))]
pub const invsqrt_a_minus_d: FieldElement = FieldElement([
6111485, 4156064, -27798727, 12243468, -25904040,
120897, 20826367, -7060776, 6093568, -1986012
]);
#[cfg(feature="radix_51")]
pub const inv_a_minus_d: FieldElement = FieldElement([
2251799813563563, 2251799813685247, 2251799813685247, 2251799813685247, 2251799813685247
]);
#[cfg(not(feature="radix_51"))]
pub const inv_a_minus_d: FieldElement = FieldElement([
-121666, 0, 0, 0, 0, 0, 0, 0, 0, 0
]);
/// (p-1)/2, in little-endian bytes.
pub const HALF_P_MINUS_1_BYTES: [u8; 32] =
@ -3247,5 +3264,10 @@ mod test {
let a = FieldElement::minus_one();
let a_minus_d = &a - &constants::d;
assert_eq!(a_minus_d, constants::a_minus_d);
let (_, invsqrt_a_minus_d) = constants::a_minus_d.invsqrt();
assert_eq!(invsqrt_a_minus_d, constants::invsqrt_a_minus_d);
let inv_a_minus_d = invsqrt_a_minus_d.square();
assert_eq!(inv_a_minus_d, constants::inv_a_minus_d);
assert_eq!(&inv_a_minus_d * &a_minus_d, FieldElement::one());
}
}