Trait Differentiable 

pub trait Differentiable {
    type Tangent: Clone;

    // Required methods
    fn zero_tangent(&self) -> Self::Tangent;
    fn accumulate_tangent(a: Self::Tangent, b: &Self::Tangent) -> Self::Tangent;
    fn num_elements(&self) -> usize;
    fn seed_cotangent(&self) -> Self::Tangent;
}

Trait defining the tangent space for a differentiable type.

This is the core abstraction of the AD framework, analogous to Julia’s ChainRulesCore.jl tangent type system. Any type that participates in automatic differentiation must implement this trait.

The tangent type represents infinitesimal perturbations of the value. For most tensor types, Tangent = Self (e.g., the tangent of a matrix is another matrix of the same shape).

Note: This trait intentionally does not require Clone on the primal type. Clone is only required on Tangent (for gradient accumulation). Large values (e.g., tensors) may be expensive to clone; the AD engine avoids cloning primals by taking ownership where needed.

Examples

use chainrules_core::Differentiable;

// Tensor<f64> implements Differentiable with Tangent = Tensor<f64>
// (defined in tenferro-tensor crate)
fn example<V: Differentiable>(x: &V) {
    let zero = x.zero_tangent();
    let _acc = V::accumulate_tangent(zero.clone(), &x.zero_tangent());
}

Required Associated Types

type Tangent: Clone

The tangent type for this value.

For most types, this is Self (e.g., tangent of a tensor is a tensor).

Required Methods

fn zero_tangent(&self) -> Self::Tangent

Returns the zero tangent for this value (additive identity).

fn accumulate_tangent(a: Self::Tangent, b: &Self::Tangent) -> Self::Tangent

Accumulates (adds) two tangents: a + b.

fn num_elements(&self) -> usize

Returns the number of scalar elements in this value.

For scalar types (f64, f32), this is always 1. For tensor types, this is the total number of elements.

fn seed_cotangent(&self) -> Self::Tangent

Returns the seed cotangent for reverse-mode pullback.

For a scalar loss, this returns the “one” tangent (1.0 for scalars, ones-like for single-element tensors). Used internally by Tape::pullback to initialize the backward pass.

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementations on Foreign Types

impl Differentiable for f32

type Tangent = f32

fn zero_tangent(&self) -> f32

fn accumulate_tangent(a: f32, b: &f32) -> f32

fn num_elements(&self) -> usize

fn seed_cotangent(&self) -> f32

impl Differentiable for f64

type Tangent = f64

fn zero_tangent(&self) -> f64

fn accumulate_tangent(a: f64, b: &f64) -> f64

fn num_elements(&self) -> usize

fn seed_cotangent(&self) -> f64

Implementors