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Generalize arithmetic ops to more combinations of scalars and arrays #782

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Generalize arithmetic ops to more combinations of scalars and arrays #782

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52ca234
Add benches for op with scalar and strided array
jturner314 Feb 15, 2020
65e13d9
Allow `&arr (op) scalar` output to be any elem type
jturner314 Feb 15, 2020
b2a7d0b
Generalize lhs scalar ops to more combos of types
jturner314 Feb 15, 2020
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16 changes: 16 additions & 0 deletions benches/bench1.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -431,6 +431,22 @@ fn scalar_add_2(bench: &mut test::Bencher) {
bench.iter(|| n + &a);
}

#[bench]
fn scalar_add_strided_1(bench: &mut test::Bencher) {
let a =
Array::from_shape_fn((64, 64 * 2), |(i, j)| (i * 64 + j) as f32).slice_move(s![.., ..;2]);
let n = 1.;
bench.iter(|| &a + n);
}

#[bench]
fn scalar_add_strided_2(bench: &mut test::Bencher) {
let a =
Array::from_shape_fn((64, 64 * 2), |(i, j)| (i * 64 + j) as f32).slice_move(s![.., ..;2]);
let n = 1.;
bench.iter(|| n + &a);
}

#[bench]
fn scalar_sub_1(bench: &mut test::Bencher) {
let a = Array::<f32, _>::zeros((64, 64));
Expand Down
144 changes: 65 additions & 79 deletions src/impl_ops.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -152,70 +152,56 @@ impl<A, S, D, B> $trt<B> for ArrayBase<S, D>
#[doc=$doc]
/// between the reference `self` and the scalar `x`,
/// and return the result as a new `Array`.
impl<'a, A, S, D, B> $trt<B> for &'a ArrayBase<S, D>
where A: Clone + $trt<B, Output=A>,
impl<'a, A, S, D, B, C> $trt<B> for &'a ArrayBase<S, D>
where A: Clone + $trt<B, Output=C>,
S: Data<Elem=A>,
D: Dimension,
B: ScalarOperand,
{
type Output = Array<A, D>;
fn $mth(self, x: B) -> Array<A, D> {
self.to_owned().$mth(x)
type Output = Array<C, D>;
fn $mth(self, x: B) -> Self::Output {
self.map(move |elt| elt.clone() $operator x.clone())
}
}
);
);

// Pick the expression $a for commutative and $b for ordered binop
macro_rules! if_commutative {
(Commute { $a:expr } or { $b:expr }) => {
$a
};
(Ordered { $a:expr } or { $b:expr }) => {
$b
};
}

macro_rules! impl_scalar_lhs_op {
// $commutative flag. Reuse the self + scalar impl if we can.
// We can do this safely since these are the primitive numeric types
($scalar:ty, $commutative:ident, $operator:tt, $trt:ident, $mth:ident, $doc:expr) => (
// these have no doc -- they are not visible in rustdoc
// Perform elementwise
// between the scalar `self` and array `rhs`,
// and return the result (based on `self`).
impl<S, D> $trt<ArrayBase<S, D>> for $scalar
where S: DataOwned<Elem=$scalar> + DataMut,
D: Dimension,
($scalar:ty, $operator:tt, $trt:ident, $mth:ident, $doc:expr) => (
/// Perform elementwise
#[doc=$doc]
/// between the scalar `self` and array `rhs`,
/// and return the result (based on `self`).
impl<A, S, D> $trt<ArrayBase<S, D>> for $scalar
where
$scalar: Clone + $trt<A, Output=A>,
A: Clone,
S: DataOwned<Elem=A> + DataMut,
D: Dimension,
{
type Output = ArrayBase<S, D>;
fn $mth(self, rhs: ArrayBase<S, D>) -> ArrayBase<S, D> {
if_commutative!($commutative {
rhs.$mth(self)
} or {{
let mut rhs = rhs;
rhs.unordered_foreach_mut(move |elt| {
*elt = self $operator *elt;
});
rhs
}})
fn $mth(self, mut rhs: ArrayBase<S, D>) -> ArrayBase<S, D> {
rhs.unordered_foreach_mut(move |elt| {
*elt = self.clone() $operator elt.clone();
});
rhs
}
}

// Perform elementwise
// between the scalar `self` and array `rhs`,
// and return the result as a new `Array`.
impl<'a, S, D> $trt<&'a ArrayBase<S, D>> for $scalar
where S: Data<Elem=$scalar>,
D: Dimension,
/// Perform elementwise
#[doc=$doc]
/// between the scalar `self` and array `rhs`,
/// and return the result as a new `Array`.
impl<'a, A, S, D, B> $trt<&'a ArrayBase<S, D>> for $scalar
where
$scalar: Clone + $trt<A, Output=B>,
A: Clone,
S: Data<Elem=A>,
D: Dimension,
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@bluss bluss Dec 29, 2020 •
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This impl somehow now breaks Rust -- see the failed tests -- and causes a recursion errror - for an expression that has type f32 + f32 which is quite strange/scary(!)

   --> tests/oper.rs:159:48
    |
159 |         .fold(f32::zero(), |acc, (&x, &y)| acc + x * y)
    |                                                ^
    |
    = help: consider adding a `#![recursion_limit="256"]` attribute to your crate (`oper`)
    = note: required because of the requirements on the impl of `Add<&ndarray::ArrayBase<_, _>>` for `f32`
    = note: required because of the requirements on the impl of `Add<&ndarray::ArrayBase<_, _>>` for `f32`
    = note: required because of the requirements on the impl of `Add<&ndarray::ArrayBase<_, _>>` for `f32`
    = note: required because of the requirements on the impl of `Add<&ndarray::ArrayBase<_, _>>` for `f32`
    = note: required because of the requirements on the impl of `Add<&ndarray::ArrayBase<_, _>>` for `f32`
    = note: required because of the requirements on the impl of `Add<&ndarray::ArrayBase<_, _>>` for `f32`
    = note: required because of the requirements on the impl of `Add<&ndarray::ArrayBase<_, _>>` for `f32`
    = note: required because of the requirements on the impl of `Add<&ndarray::ArrayBase<_, _>>` for `f32`

Unsure if this is a Rust bug - for example that the impl is accepted(?), but I think this impl is too general and has infinite descent.

Given the question if f32 implements Add<&ArrayBase<S, D>> look for other impl that has f32: Add<A> where S: Data<Elem=A> which looks recursive, is that it?

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It looks like a compiler bug to me. As you point out, the expression involves only f32, but for some reason, the error message indicates that one of the arguments is an array. It's also interesting that on my machine with Rust 1.48.0, the error message is slightly different, saying "impl of Add<ndarray::ArrayBase<_, _>> for f32" instead of the error message in your comment "impl of Add<&ndarray::ArrayBase<_, _>> for f32". (Note the &.)

The function fails to compile (with the same error message) even after adding type annotations:

fn reference_dot<'a, V1, V2>(a: V1, b: V2) -> f32
where
    V1: AsArray<'a, f32>,
    V2: AsArray<'a, f32>,
{
    let a: ArrayView1<'a, f32> = a.into();
    let b: ArrayView1<'a, f32> = b.into();
    a.iter()
        .zip(b.iter())
        .fold(f32::zero(), |acc: f32, (&x, &y): (&f32, &f32)| acc + x * y)
}

but if I remove the + x * y, it compiles successfully:

fn reference_dot<'a, V1, V2>(a: V1, b: V2) -> f32
where
    V1: AsArray<'a, f32>,
    V2: AsArray<'a, f32>,
{
    let a: ArrayView1<'a, f32> = a.into();
    let b: ArrayView1<'a, f32> = b.into();
    a.iter()
        .zip(b.iter())
        .fold(f32::zero(), |acc: f32, (&x, &y): (&f32, &f32)| acc)
}

I don't see any reason other than a compiler bug for the first function to fail to compile when the second one compiles without errors, since the type annotations confirm that the closure is operating only on f32 values.

This also compiles successfully:

fn reference_dot2<'a>(a: ArrayView1<'a, f32>, b: ArrayView1<'a, f32>) -> f32 {
    a.iter()
        .zip(b.iter())
        .fold(f32::zero(), |acc: f32, (&x, &y): (&f32, &f32)| acc + x * y)
}

so the bug involves the .into() calls in some way. It's surprising that adding explicit type annotations for the results of the .into() calls, as in the first example, doesn't work around the bug.

Fwiw, I don't think impl<'a, A, S, D, B> $trt<&'a ArrayBase<S, D>> for $scalar is infinitely recursive, since AFAIK it's not possible to have an array of (arrays of (arrays of (arrays of ... [infinite depth]))). The innermost array type can only have an element type that's not an array. You're right that there is recursion if you're dealing with arrays of arrays, but that's the correct behavior, and the recursion is not infinite.

For the particular function we're looking at, the impl doesn't apply, and I don't think the compiler should be trying to apply it. (I think it should only apply the impl if it knows the RHS has some type &ArrayBase<?S, ?D>, where ?S and ?D are inference variables.)

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@bluss bluss Dec 30, 2020 •
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Interesting, the test runners for cross_test, stable, mips vs i686 disagree with each other about the error too, in the same way, even if they both use Rust 1.48

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I reported the issue (with a simplified example) at rust-lang/rust#80542.

{
type Output = Array<$scalar, D>;
fn $mth(self, rhs: &ArrayBase<S, D>) -> Array<$scalar, D> {
if_commutative!($commutative {
rhs.$mth(self)
} or {
self.$mth(rhs.to_owned())
})
type Output = Array<B, D>;
fn $mth(self, rhs: &ArrayBase<S, D>) -> Array<B, D> {
rhs.map(move |elt| self.clone() $operator elt.clone())
}
}
);
Expand All @@ -241,16 +227,16 @@ mod arithmetic_ops {

macro_rules! all_scalar_ops {
($int_scalar:ty) => (
impl_scalar_lhs_op!($int_scalar, Commute, +, Add, add, "addition");
impl_scalar_lhs_op!($int_scalar, Ordered, -, Sub, sub, "subtraction");
impl_scalar_lhs_op!($int_scalar, Commute, *, Mul, mul, "multiplication");
impl_scalar_lhs_op!($int_scalar, Ordered, /, Div, div, "division");
impl_scalar_lhs_op!($int_scalar, Ordered, %, Rem, rem, "remainder");
impl_scalar_lhs_op!($int_scalar, Commute, &, BitAnd, bitand, "bit and");
impl_scalar_lhs_op!($int_scalar, Commute, |, BitOr, bitor, "bit or");
impl_scalar_lhs_op!($int_scalar, Commute, ^, BitXor, bitxor, "bit xor");
impl_scalar_lhs_op!($int_scalar, Ordered, <<, Shl, shl, "left shift");
impl_scalar_lhs_op!($int_scalar, Ordered, >>, Shr, shr, "right shift");
impl_scalar_lhs_op!($int_scalar, +, Add, add, "addition");
impl_scalar_lhs_op!($int_scalar, -, Sub, sub, "subtraction");
impl_scalar_lhs_op!($int_scalar, *, Mul, mul, "multiplication");
impl_scalar_lhs_op!($int_scalar, /, Div, div, "division");
impl_scalar_lhs_op!($int_scalar, %, Rem, rem, "remainder");
impl_scalar_lhs_op!($int_scalar, &, BitAnd, bitand, "bit and");
impl_scalar_lhs_op!($int_scalar, |, BitOr, bitor, "bit or");
impl_scalar_lhs_op!($int_scalar, ^, BitXor, bitxor, "bit xor");
impl_scalar_lhs_op!($int_scalar, <<, Shl, shl, "left shift");
impl_scalar_lhs_op!($int_scalar, >>, Shr, shr, "right shift");
);
}
all_scalar_ops!(i8);
Expand All @@ -264,31 +250,31 @@ mod arithmetic_ops {
all_scalar_ops!(i128);
all_scalar_ops!(u128);

impl_scalar_lhs_op!(bool, Commute, &, BitAnd, bitand, "bit and");
impl_scalar_lhs_op!(bool, Commute, |, BitOr, bitor, "bit or");
impl_scalar_lhs_op!(bool, Commute, ^, BitXor, bitxor, "bit xor");
impl_scalar_lhs_op!(bool, &, BitAnd, bitand, "bit and");
impl_scalar_lhs_op!(bool, |, BitOr, bitor, "bit or");
impl_scalar_lhs_op!(bool, ^, BitXor, bitxor, "bit xor");

impl_scalar_lhs_op!(f32, Commute, +, Add, add, "addition");
impl_scalar_lhs_op!(f32, Ordered, -, Sub, sub, "subtraction");
impl_scalar_lhs_op!(f32, Commute, *, Mul, mul, "multiplication");
impl_scalar_lhs_op!(f32, Ordered, /, Div, div, "division");
impl_scalar_lhs_op!(f32, Ordered, %, Rem, rem, "remainder");
impl_scalar_lhs_op!(f32, +, Add, add, "addition");
impl_scalar_lhs_op!(f32, -, Sub, sub, "subtraction");
impl_scalar_lhs_op!(f32, *, Mul, mul, "multiplication");
impl_scalar_lhs_op!(f32, /, Div, div, "division");
impl_scalar_lhs_op!(f32, %, Rem, rem, "remainder");

impl_scalar_lhs_op!(f64, Commute, +, Add, add, "addition");
impl_scalar_lhs_op!(f64, Ordered, -, Sub, sub, "subtraction");
impl_scalar_lhs_op!(f64, Commute, *, Mul, mul, "multiplication");
impl_scalar_lhs_op!(f64, Ordered, /, Div, div, "division");
impl_scalar_lhs_op!(f64, Ordered, %, Rem, rem, "remainder");
impl_scalar_lhs_op!(f64, +, Add, add, "addition");
impl_scalar_lhs_op!(f64, -, Sub, sub, "subtraction");
impl_scalar_lhs_op!(f64, *, Mul, mul, "multiplication");
impl_scalar_lhs_op!(f64, /, Div, div, "division");
impl_scalar_lhs_op!(f64, %, Rem, rem, "remainder");

impl_scalar_lhs_op!(Complex<f32>, Commute, +, Add, add, "addition");
impl_scalar_lhs_op!(Complex<f32>, Ordered, -, Sub, sub, "subtraction");
impl_scalar_lhs_op!(Complex<f32>, Commute, *, Mul, mul, "multiplication");
impl_scalar_lhs_op!(Complex<f32>, Ordered, /, Div, div, "division");
impl_scalar_lhs_op!(Complex<f32>, +, Add, add, "addition");
impl_scalar_lhs_op!(Complex<f32>, -, Sub, sub, "subtraction");
impl_scalar_lhs_op!(Complex<f32>, *, Mul, mul, "multiplication");
impl_scalar_lhs_op!(Complex<f32>, /, Div, div, "division");

impl_scalar_lhs_op!(Complex<f64>, Commute, +, Add, add, "addition");
impl_scalar_lhs_op!(Complex<f64>, Ordered, -, Sub, sub, "subtraction");
impl_scalar_lhs_op!(Complex<f64>, Commute, *, Mul, mul, "multiplication");
impl_scalar_lhs_op!(Complex<f64>, Ordered, /, Div, div, "division");
impl_scalar_lhs_op!(Complex<f64>, +, Add, add, "addition");
impl_scalar_lhs_op!(Complex<f64>, -, Sub, sub, "subtraction");
impl_scalar_lhs_op!(Complex<f64>, *, Mul, mul, "multiplication");
impl_scalar_lhs_op!(Complex<f64>, /, Div, div, "division");

impl<A, S, D> Neg for ArrayBase<S, D>
where
Expand Down