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div with differently sized denominators #799

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3bcc7e3
Implement `div_rem` for smaller sized denominators
erik-3milabs Mar 31, 2025
dac7678
Implement `div_rem` for larger denominators
erik-3milabs Mar 31, 2025
41c328b
Clean up `Uint::rem_mixed` test
erik-3milabs Mar 31, 2025
0883c63
Implement `Uint::div` traits
erik-3milabs Mar 31, 2025
a147ed9
Implement `Int::div` traits
erik-3milabs Mar 31, 2025
10eec67
Implement `Int::div_uint` traits
erik-3milabs Mar 31, 2025
6b004a4
Update `Uint::div` benchmarks
erik-3milabs Mar 31, 2025
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55 changes: 51 additions & 4 deletions benches/uint.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -219,7 +219,19 @@ fn bench_division(c: &mut Criterion) {
let mut rng = make_rng();
let mut group = c.benchmark_group("wrapping ops");

group.bench_function("div/rem, U256/U128, full size", |b| {
group.bench_function("div/rem, U256/U128", |b| {
b.iter_batched(
|| {
let x = U256::random(&mut rng);
let y = U128::random(&mut rng);
(x, NonZero::new(y).unwrap())
},
|(x, y)| black_box(x.div_rem(&y)),
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Just a side node, you don't need to wrap the output in black_box, Criterion already does that for all iter* methods.

BatchSize::SmallInput,
)
});

group.bench_function("div/rem, U256/U128 (in U256)", |b| {
b.iter_batched(
|| {
let x = U256::random(&mut rng);
Expand All @@ -232,6 +244,18 @@ fn bench_division(c: &mut Criterion) {
)
});

group.bench_function("div/rem, U256/U128 (in U512)", |b| {
b.iter_batched(
|| {
let x = U256::random(&mut rng);
let y: U512 = U128::random(&mut rng).resize();
(x, NonZero::new(y).unwrap())
},
|(x, y)| black_box(x.div_rem(&y)),
BatchSize::SmallInput,
)
});

group.bench_function("div/rem_vartime, U256/U128, full size", |b| {
b.iter_batched(
|| {
Expand All @@ -244,12 +268,35 @@ fn bench_division(c: &mut Criterion) {
)
});

group.bench_function("rem, U256/U128, full size", |b| {
group.bench_function("rem, U256/U128", |b| {
b.iter_batched(
|| {
let x = U256::random(&mut rng);
let y_half = U128::random(&mut rng);
let y: U256 = (y_half, U128::ZERO).into();
let y = U128::random(&mut rng);
(x, NonZero::new(y).unwrap())
},
|(x, y)| black_box(x.rem(&y)),
BatchSize::SmallInput,
)
});

group.bench_function("rem, U256/U128 (in U256)", |b| {
b.iter_batched(
|| {
let x = U256::random(&mut rng);
let y: U256 = U128::random(&mut rng).resize();
(x, NonZero::new(y).unwrap())
},
|(x, y)| black_box(x.rem(&y)),
BatchSize::SmallInput,
)
});

group.bench_function("rem, U256/U128 (in U512)", |b| {
b.iter_batched(
|| {
let x = U256::random(&mut rng);
let y: U512 = U128::random(&mut rng).resize();
(x, NonZero::new(y).unwrap())
},
|(x, y)| black_box(x.rem(&y)),
Expand Down
128 changes: 78 additions & 50 deletions src/int/div.rs
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -13,10 +13,10 @@ impl<const LIMBS: usize> Int<LIMBS> {
///
/// Computes the quotient and remainder of `self / rhs`.
/// Furthermore, returns the signs of `self` and `rhs`.
const fn div_rem_base(
const fn div_rem_base<const RHS_LIMBS: usize>(
&self,
rhs: &NonZero<Self>,
) -> (Uint<{ LIMBS }>, Uint<{ LIMBS }>, ConstChoice, ConstChoice) {
rhs: &NonZero<Int<RHS_LIMBS>>,
) -> (Uint<LIMBS>, Uint<RHS_LIMBS>, ConstChoice, ConstChoice) {
// Step 1: split operands into signs and magnitudes.
let (lhs_mag, lhs_sgn) = self.abs_sign();
let (rhs_mag, rhs_sgn) = rhs.abs_sign();
Expand Down Expand Up @@ -52,7 +52,10 @@ impl<const LIMBS: usize> Int<LIMBS> {
/// assert_eq!(quotient.unwrap(), I128::from(2));
/// assert_eq!(remainder, I128::from(-2));
/// ```
pub const fn checked_div_rem(&self, rhs: &NonZero<Self>) -> (ConstCtOption<Self>, Self) {
pub const fn checked_div_rem<const RHS_LIMBS: usize>(
&self,
rhs: &NonZero<Int<RHS_LIMBS>>,
) -> (ConstCtOption<Self>, Int<RHS_LIMBS>) {
let (quotient, remainder, lhs_sgn, rhs_sgn) = self.div_rem_base(rhs);
let opposing_signs = lhs_sgn.ne(rhs_sgn);
(
Expand All @@ -66,12 +69,15 @@ impl<const LIMBS: usize> Int<LIMBS> {
/// - `self != MIN` or `rhs != MINUS_ONE`.
///
/// Note: this operation rounds towards zero, truncating any fractional part of the exact result.
pub fn checked_div(&self, rhs: &Self) -> CtOption<Self> {
pub fn checked_div<const RHS_LIMBS: usize>(&self, rhs: &Int<RHS_LIMBS>) -> CtOption<Self> {
NonZero::new(*rhs).and_then(|rhs| self.checked_div_rem(&rhs).0.into())
}

/// Computes `self` % `rhs`, returns the remainder.
pub const fn rem(&self, rhs: &NonZero<Self>) -> Self {
pub const fn rem<const RHS_LIMBS: usize>(
&self,
rhs: &NonZero<Int<RHS_LIMBS>>,
) -> Int<RHS_LIMBS> {
self.checked_div_rem(rhs).1
}
}
Expand Down Expand Up @@ -223,7 +229,10 @@ impl<const LIMBS: usize> Int<LIMBS> {
/// I128::from(2)
/// )
/// ```
pub fn checked_div_floor(&self, rhs: &Self) -> CtOption<Self> {
pub fn checked_div_floor<const RHS_LIMBS: usize>(
&self,
rhs: &Int<RHS_LIMBS>,
) -> CtOption<Self> {
NonZero::new(*rhs).and_then(|rhs| self.checked_div_rem_floor(&rhs).0.into())
}

Expand Down Expand Up @@ -257,7 +266,10 @@ impl<const LIMBS: usize> Int<LIMBS> {
/// assert_eq!(quotient.unwrap(), I128::from(2));
/// assert_eq!(remainder, I128::from(2));
/// ```
pub const fn checked_div_rem_floor(&self, rhs: &NonZero<Self>) -> (ConstCtOption<Self>, Self) {
pub const fn checked_div_rem_floor<const RHS_LIMBS: usize>(
&self,
rhs: &NonZero<Int<RHS_LIMBS>>,
) -> (ConstCtOption<Self>, Int<RHS_LIMBS>) {
let (lhs_mag, lhs_sgn) = self.abs_sign();
let (rhs_mag, rhs_sgn) = rhs.abs_sign();
let (quotient, remainder) = lhs_mag.div_rem(&rhs_mag);
Expand All @@ -283,40 +295,40 @@ impl<const LIMBS: usize> Int<LIMBS> {
}
}

impl<const LIMBS: usize> CheckedDiv for Int<LIMBS> {
fn checked_div(&self, rhs: &Int<LIMBS>) -> CtOption<Self> {
impl<const LIMBS: usize, const RHS_LIMBS: usize> CheckedDiv<Int<RHS_LIMBS>> for Int<LIMBS> {
fn checked_div(&self, rhs: &Int<RHS_LIMBS>) -> CtOption<Self> {
self.checked_div(rhs)
}
}

impl<const LIMBS: usize> Div<&NonZero<Int<LIMBS>>> for &Int<LIMBS> {
impl<const LIMBS: usize, const RHS_LIMBS: usize> Div<&NonZero<Int<RHS_LIMBS>>> for &Int<LIMBS> {
type Output = CtOption<Int<LIMBS>>;

fn div(self, rhs: &NonZero<Int<LIMBS>>) -> Self::Output {
fn div(self, rhs: &NonZero<Int<RHS_LIMBS>>) -> Self::Output {
*self / *rhs
}
}

impl<const LIMBS: usize> Div<&NonZero<Int<LIMBS>>> for Int<LIMBS> {
impl<const LIMBS: usize, const RHS_LIMBS: usize> Div<&NonZero<Int<RHS_LIMBS>>> for Int<LIMBS> {
type Output = CtOption<Int<LIMBS>>;

fn div(self, rhs: &NonZero<Int<LIMBS>>) -> Self::Output {
fn div(self, rhs: &NonZero<Int<RHS_LIMBS>>) -> Self::Output {
self / *rhs
}
}

impl<const LIMBS: usize> Div<NonZero<Int<LIMBS>>> for &Int<LIMBS> {
impl<const LIMBS: usize, const RHS_LIMBS: usize> Div<NonZero<Int<RHS_LIMBS>>> for &Int<LIMBS> {
type Output = CtOption<Int<LIMBS>>;

fn div(self, rhs: NonZero<Int<LIMBS>>) -> Self::Output {
fn div(self, rhs: NonZero<Int<RHS_LIMBS>>) -> Self::Output {
*self / rhs
}
}

impl<const LIMBS: usize> Div<NonZero<Int<LIMBS>>> for Int<LIMBS> {
impl<const LIMBS: usize, const RHS_LIMBS: usize> Div<NonZero<Int<RHS_LIMBS>>> for Int<LIMBS> {
type Output = CtOption<Int<LIMBS>>;

fn div(self, rhs: NonZero<Int<LIMBS>>) -> Self::Output {
fn div(self, rhs: NonZero<Int<RHS_LIMBS>>) -> Self::Output {
self.checked_div(&rhs)
}
}
Expand All @@ -333,34 +345,42 @@ impl<const LIMBS: usize> DivAssign<NonZero<Int<LIMBS>>> for Int<LIMBS> {
}
}

impl<const LIMBS: usize> Div<NonZero<Int<LIMBS>>> for Wrapping<Int<LIMBS>> {
impl<const LIMBS: usize, const RHS_LIMBS: usize> Div<NonZero<Int<RHS_LIMBS>>>
for Wrapping<Int<LIMBS>>
{
type Output = Wrapping<Int<LIMBS>>;

fn div(self, rhs: NonZero<Int<LIMBS>>) -> Self::Output {
fn div(self, rhs: NonZero<Int<RHS_LIMBS>>) -> Self::Output {
Wrapping((self.0 / rhs).expect("cannot represent positive equivalent of Int::MIN as int"))
}
}

impl<const LIMBS: usize> Div<NonZero<Int<LIMBS>>> for &Wrapping<Int<LIMBS>> {
impl<const LIMBS: usize, const RHS_LIMBS: usize> Div<NonZero<Int<RHS_LIMBS>>>
for &Wrapping<Int<LIMBS>>
{
type Output = Wrapping<Int<LIMBS>>;

fn div(self, rhs: NonZero<Int<LIMBS>>) -> Self::Output {
fn div(self, rhs: NonZero<Int<RHS_LIMBS>>) -> Self::Output {
*self / rhs
}
}

impl<const LIMBS: usize> Div<&NonZero<Int<LIMBS>>> for &Wrapping<Int<LIMBS>> {
impl<const LIMBS: usize, const RHS_LIMBS: usize> Div<&NonZero<Int<RHS_LIMBS>>>
for &Wrapping<Int<LIMBS>>
{
type Output = Wrapping<Int<LIMBS>>;

fn div(self, rhs: &NonZero<Int<LIMBS>>) -> Self::Output {
fn div(self, rhs: &NonZero<Int<RHS_LIMBS>>) -> Self::Output {
*self / *rhs
}
}

impl<const LIMBS: usize> Div<&NonZero<Int<LIMBS>>> for Wrapping<Int<LIMBS>> {
impl<const LIMBS: usize, const RHS_LIMBS: usize> Div<&NonZero<Int<RHS_LIMBS>>>
for Wrapping<Int<LIMBS>>
{
type Output = Wrapping<Int<LIMBS>>;

fn div(self, rhs: &NonZero<Int<LIMBS>>) -> Self::Output {
fn div(self, rhs: &NonZero<Int<RHS_LIMBS>>) -> Self::Output {
self / *rhs
}
}
Expand All @@ -379,34 +399,34 @@ impl<const LIMBS: usize> DivAssign<NonZero<Int<LIMBS>>> for Wrapping<Int<LIMBS>>
}
}

impl<const LIMBS: usize> Rem<&NonZero<Int<LIMBS>>> for &Int<LIMBS> {
type Output = Int<LIMBS>;
impl<const LIMBS: usize, const RHS_LIMBS: usize> Rem<&NonZero<Int<RHS_LIMBS>>> for &Int<LIMBS> {
type Output = Int<RHS_LIMBS>;

fn rem(self, rhs: &NonZero<Int<LIMBS>>) -> Self::Output {
fn rem(self, rhs: &NonZero<Int<RHS_LIMBS>>) -> Self::Output {
*self % *rhs
}
}

impl<const LIMBS: usize> Rem<&NonZero<Int<LIMBS>>> for Int<LIMBS> {
type Output = Int<LIMBS>;
impl<const LIMBS: usize, const RHS_LIMBS: usize> Rem<&NonZero<Int<RHS_LIMBS>>> for Int<LIMBS> {
type Output = Int<RHS_LIMBS>;

fn rem(self, rhs: &NonZero<Int<LIMBS>>) -> Self::Output {
fn rem(self, rhs: &NonZero<Int<RHS_LIMBS>>) -> Self::Output {
self % *rhs
}
}

impl<const LIMBS: usize> Rem<NonZero<Int<LIMBS>>> for &Int<LIMBS> {
type Output = Int<LIMBS>;
impl<const LIMBS: usize, const RHS_LIMBS: usize> Rem<NonZero<Int<RHS_LIMBS>>> for &Int<LIMBS> {
type Output = Int<RHS_LIMBS>;

fn rem(self, rhs: NonZero<Int<LIMBS>>) -> Self::Output {
fn rem(self, rhs: NonZero<Int<RHS_LIMBS>>) -> Self::Output {
*self % rhs
}
}

impl<const LIMBS: usize> Rem<NonZero<Int<LIMBS>>> for Int<LIMBS> {
type Output = Int<LIMBS>;
impl<const LIMBS: usize, const RHS_LIMBS: usize> Rem<NonZero<Int<RHS_LIMBS>>> for Int<LIMBS> {
type Output = Int<RHS_LIMBS>;

fn rem(self, rhs: NonZero<Int<LIMBS>>) -> Self::Output {
fn rem(self, rhs: NonZero<Int<RHS_LIMBS>>) -> Self::Output {
Self::rem(&self, &rhs)
}
}
Expand All @@ -423,34 +443,42 @@ impl<const LIMBS: usize> RemAssign<NonZero<Int<LIMBS>>> for Int<LIMBS> {
}
}

impl<const LIMBS: usize> Rem<NonZero<Int<LIMBS>>> for Wrapping<Int<LIMBS>> {
type Output = Wrapping<Int<LIMBS>>;
impl<const LIMBS: usize, const RHS_LIMBS: usize> Rem<NonZero<Int<RHS_LIMBS>>>
for Wrapping<Int<LIMBS>>
{
type Output = Wrapping<Int<RHS_LIMBS>>;

fn rem(self, rhs: NonZero<Int<LIMBS>>) -> Self::Output {
fn rem(self, rhs: NonZero<Int<RHS_LIMBS>>) -> Self::Output {
Wrapping(self.0 % rhs)
}
}

impl<const LIMBS: usize> Rem<NonZero<Int<LIMBS>>> for &Wrapping<Int<LIMBS>> {
type Output = Wrapping<Int<LIMBS>>;
impl<const LIMBS: usize, const RHS_LIMBS: usize> Rem<NonZero<Int<RHS_LIMBS>>>
for &Wrapping<Int<LIMBS>>
{
type Output = Wrapping<Int<RHS_LIMBS>>;

fn rem(self, rhs: NonZero<Int<LIMBS>>) -> Self::Output {
fn rem(self, rhs: NonZero<Int<RHS_LIMBS>>) -> Self::Output {
*self % rhs
}
}

impl<const LIMBS: usize> Rem<&NonZero<Int<LIMBS>>> for &Wrapping<Int<LIMBS>> {
type Output = Wrapping<Int<LIMBS>>;
impl<const LIMBS: usize, const RHS_LIMBS: usize> Rem<&NonZero<Int<RHS_LIMBS>>>
for &Wrapping<Int<LIMBS>>
{
type Output = Wrapping<Int<RHS_LIMBS>>;

fn rem(self, rhs: &NonZero<Int<LIMBS>>) -> Self::Output {
fn rem(self, rhs: &NonZero<Int<RHS_LIMBS>>) -> Self::Output {
*self % *rhs
}
}

impl<const LIMBS: usize> Rem<&NonZero<Int<LIMBS>>> for Wrapping<Int<LIMBS>> {
type Output = Wrapping<Int<LIMBS>>;
impl<const LIMBS: usize, const RHS_LIMBS: usize> Rem<&NonZero<Int<RHS_LIMBS>>>
for Wrapping<Int<LIMBS>>
{
type Output = Wrapping<Int<RHS_LIMBS>>;

fn rem(self, rhs: &NonZero<Int<LIMBS>>) -> Self::Output {
fn rem(self, rhs: &NonZero<Int<RHS_LIMBS>>) -> Self::Output {
self % *rhs
}
}
Expand Down
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