DiffMode in rustc_ast::expand::autodiff_attrs - Rust
Description: Forward and Reverse Mode are well known names for automatic differentiation implementations. Enzyme does support both, but with different semantics, see DiffActivity. The First variants are a hack to support higher order derivatives. We need to compute first order derivatives before we compute second order derivatives, otherwise we would differentiate our placeholder functions. The proper solution is to recognize and resolve this DAG of autodiff invocations, as it’s already done in the C++ and Julia frontend of Enzyme.

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## DiffMode

# Enum DiffMode

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    pub enum DiffMode {
        Error,
        Source,
        Forward,
        Reverse,
    }

Expand description

Forward and Reverse Mode are well known names for automatic differentiation implementations. Enzyme does support both, but with different semantics, see DiffActivity. The First variants are a hack to support higher order derivatives. We need to compute first order derivatives before we compute second order derivatives, otherwise we would differentiate our placeholder functions. The proper solution is to recognize and resolve this DAG of autodiff invocations, as it’s already done in the C++ and Julia frontend of Enzyme.

Documentation for using reverse and forward mode is available online.

## Variants§

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### Error

No autodiff is applied (used during error handling).

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### Source

The primal function which we will differentiate.

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### Forward

The target function, to be created using forward mode AD.

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### Reverse

The target function, to be created using reverse mode AD.

## Implementations§

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### impl DiffMode

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#### pub fn all_modes() -> &'static [Symbol]

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### impl DiffMode

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#### pub fn is_rev(&self) -> bool

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#### pub fn is_fwd(&self) -> bool

## Trait Implementations§

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### impl Clone for DiffMode

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#### fn clone(&self) -> DiffMode

Returns a duplicate of the value. Read more
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#### fn clone_from(&mut self, source: &Self)

Performs copy-assignment from `source`. Read more
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### impl Debug for DiffMode

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#### fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more
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### impl<__D: SpanDecoder> Decodable<__D> for DiffMode

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#### fn decode(__decoder: &mut __D) -> Self

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### impl Display for DiffMode

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#### fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more
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### impl<__E: SpanEncoder> Encodable<__E> for DiffMode

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#### fn encode(&self, __encoder: &mut __E)

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### impl FromStr for DiffMode

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#### type Err = ()

The associated error which can be returned from parsing.
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#### fn from_str(s: &str) -> Result<DiffMode, ()>

Parses a string `s` to return a value of this type. Read more
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### impl PartialEq for DiffMode

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#### fn eq(&self, other: &DiffMode) -> bool

Tests for `self` and `other` values to be equal, and is used by `==`.
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#### fn ne(&self, other: &Rhs) -> bool

Tests for `!=`. The default implementation is almost always sufficient, and should not be overridden without very good reason.
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### impl StableHash for DiffMode

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#### fn stable_hash<__Hcx: StableHashCtxt>( &self, __hcx: &mut __Hcx, __hasher: &mut StableHasher, )

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### impl Copy for DiffMode

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### impl Eq for DiffMode

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### impl StructuralPartialEq for DiffMode

## Auto Trait Implementations§

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### impl DynSend for DiffMode

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### impl DynSync for DiffMode

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### impl Freeze for DiffMode

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### impl RefUnwindSafe for DiffMode

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### impl Send for DiffMode

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### impl Sync for DiffMode

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### impl Unpin for DiffMode

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### impl UnsafeUnpin for DiffMode

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### impl UnwindSafe for DiffMode

## Blanket Implementations§

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### impl<T> Aligned for T

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#### const ALIGN: Alignment

Alignment of `Self`.
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### impl<T> Any for T
where T: 'static + ?Sized,

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#### fn type_id(&self) -> TypeId

Gets the `TypeId` of `self`. Read more
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### impl<T> Borrow<T> for T
where T: ?Sized,

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#### fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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### impl<T> BorrowMut<T> for T
where T: ?Sized,

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#### fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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### impl<T> CloneToUninit for T
where T: Clone,

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#### unsafe fn clone_to_uninit(&self, dest: *mut u8)

🔬This is a nightly-only experimental API. (`clone_to_uninit`)
Performs copy-assignment from `self` to `dest`. Read more
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### impl<Q, K> Equivalent<K> for Q
where Q: Eq + ?Sized, K: Borrow<Q> + ?Sized,

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#### fn equivalent(&self, key: &K) -> bool

Checks if this value is equivalent to the given key. Read more
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### impl<Q, K> Equivalent<K> for Q
where Q: Eq + ?Sized, K: Borrow<Q> + ?Sized,

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#### fn equivalent(&self, key: &K) -> bool

Checks if this value is equivalent to the given key. Read more
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### impl<Q, K> Equivalent<K> for Q
where Q: Eq + ?Sized, K: Borrow<Q> + ?Sized,

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#### fn equivalent(&self, key: &K) -> bool

Compare self to `key` and return `true` if they are equal.
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### impl<T> From<T> for T

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#### fn from(t: T) -> T

Returns the argument unchanged.

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### impl<T> Instrument for T

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#### fn instrument(self, span: Span) -> Instrumented<Self>

Instruments this type with the provided `Span`, returning an `Instrumented` wrapper. Read more
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#### fn in_current_span(self) -> Instrumented<Self>

Instruments this type with the current `Span`, returning an `Instrumented` wrapper. Read more
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### impl<T, U> Into<U> for T
where U: From<T>,

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#### fn into(self) -> U

Calls `U::from(self)`.

That is, this conversion is whatever the implementation of `From<T> for U` chooses to do.

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### impl<T> IntoEither for T

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#### fn into_either(self, into_left: bool) -> Either<Self, Self>

Converts `self` into a `Left` variant of `Either<Self, Self>` if `into_left` is `true`. Converts `self` into a `Right` variant of `Either<Self, Self>` otherwise. Read more
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#### fn into_either_with<F>(self, into_left: F) -> Either<Self, Self>
where F: FnOnce(&Self) -> bool,

Converts `self` into a `Left` variant of `Either<Self, Self>` if `into_left(&self)` returns `true`. Converts `self` into a `Right` variant of `Either<Self, Self>` otherwise. Read more
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### impl<T> MutVisitorResult for T

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#### type Result = ()

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### impl<T> Pointable for T

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#### const ALIGN: usize

The alignment of pointer.
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#### type Init = T

The type for initializers.
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#### unsafe fn init(init: <T as Pointable>::Init) -> usize

Initializes a with the given initializer. Read more
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#### unsafe fn deref<'a>(ptr: usize) -> &'a T

Dereferences the given pointer. Read more
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#### unsafe fn deref_mut<'a>(ptr: usize) -> &'a mut T

Mutably dereferences the given pointer. Read more
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#### unsafe fn drop(ptr: usize)

Drops the object pointed to by the given pointer. Read more
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### impl<T> Same for T

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#### type Output = T

Should always be `Self`
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### impl<T> ToOwned for T
where T: Clone,

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#### type Owned = T

The resulting type after obtaining ownership.
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#### fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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#### fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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### impl<T> ToString for T
where T: Display + ?Sized,

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#### fn to_string(&self) -> String

Converts the given value to a `String`. Read more
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### impl<T, U> TryFrom<U> for T
where U: Into<T>,

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#### type Error = Infallible

The type returned in the event of a conversion error.
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#### fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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### impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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#### type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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#### fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
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### impl<T> WithSubscriber for T

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#### fn with_subscriber<S>(self, subscriber: S) -> WithDispatch<Self>
where S: Into<Dispatch>,

Attaches the provided `Subscriber` to this type, returning a `WithDispatch` wrapper. Read more
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#### fn with_current_subscriber(self) -> WithDispatch<Self>

Attaches the current default `Subscriber` to this type, returning a `WithDispatch` wrapper. Read more

## Layout§

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain `repr(...)` attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.

Size: 1 byte

Size for each variant:

- `Error`: 0 bytes
- `Source`: 0 bytes
- `Forward`: 0 bytes
- `Reverse`: 0 bytes