Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

feat: remove byte decomposition in compute_decomposition #6159

Merged
merged 4 commits into from
Oct 10, 2024
Merged

feat: remove byte decomposition in compute_decomposition #6159

Changes from all commits
Commits
Show all changes
4 commits
Select commit Hold shift + click to select a range
5f3c41c
feat: remove byte decomposition in `compute_decomposition`
TomAFrench Sep 26, 2024
741b1d9
Update noir_stdlib/src/field/bn254.nr
TomAFrench Sep 27, 2024
56a3a44
Merge branch 'master' into tf/poor-mans-field-integer-division
TomAFrench Sep 27, 2024
6cdf91c
Merge branch 'master' into tf/poor-mans-field-integer-division
TomAFrench Oct 10, 2024
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
22 changes: 10 additions & 12 deletions noir_stdlib/src/field/bn254.nr
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -5,20 +5,18 @@ global PLO: Field = 53438638232309528389504892708671455233;
global PHI: Field = 64323764613183177041862057485226039389;

pub(crate) global TWO_POW_128: Field = 0x100000000000000000000000000000000;
global TWO_POW_64: Field = 0x10000000000000000;

// Decomposes a single field into two 16 byte fields.
fn compute_decomposition(x: Field) -> (Field, Field) {
let x_bytes: [u8; 32] = x.to_le_bytes();

let mut low: Field = 0;
let mut high: Field = 0;

let mut offset = 1;
for i in 0..16 {
low += (x_bytes[i] as Field) * offset;
high += (x_bytes[i + 16] as Field) * offset;
offset *= 256;
}
fn compute_decomposition(mut x: Field) -> (Field, Field) {
// Here's we're taking advantage of truncating 64 bit limbs from the input field
// and then subtracting them from the input such the field division is equivalent to integer division.
let low_lower_64 = (x as u64) as Field;
x = (x - low_lower_64) / TWO_POW_64;
let low_upper_64 = (x as u64) as Field;

let high = (x - low_upper_64) / TWO_POW_64;
let low = low_upper_64 * TWO_POW_64 + low_lower_64;

(low, high)
}
Expand Down
Loading