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[AutoDiff] Change gradient(at:in:) to gradient(at:of:) #40884

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Jan 17, 2022
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[AutoDiff] Change gradient(at:in:) to gradient(at:of:) #40884

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8 changes: 4 additions & 4 deletions docs/DifferentiableProgrammingImplementation.md
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Expand Up @@ -34,7 +34,7 @@ This document explains how differentiation is implemented in the Swift compiler,

```swift
// From the standard library:
// func gradient<T, R>(at x: T, in f: @differentiable (T) -> R) -> T.TangentVector
// func gradient<T, R>(at x: T, of f: @differentiable (T) -> R) -> T.TangentVector
// where R: FloatingPoint, R.TangentVector == R

// 1. What does the `@differentiable` attribute do?
Expand All @@ -51,7 +51,7 @@ func cubed(_ x: Float) -> Float {
// transform generates derivative functions for the closure expression. The
// `gradient` higher-order function extracts and applies a derivative function to
// evaluate a gradient value.
gradient(at: 4, in: { x in x * x * x }) // 48.0
gradient(at: 4, of: { x in x * x * x }) // 48.0
```

> NOTE:
Expand Down Expand Up @@ -397,13 +397,13 @@ func cubed(_ x: Float) -> Float {
// %cubed = differentiable_function [wrt 0] %closure_ref
// with {%closure_jvp_ref, %closure_vjp_ref}

gradient(at: Float(4), in: { x in x * x * x })
gradient(at: Float(4), of: { x in x * x * x })

// Swift supports implicit function conversions, which happens above.
// Below is what the conversion looks like explicitly:
// let foo: (Float) -> Float = { x in x * x * x }
// let cubed: @differentiable (Float) -> Float = foo
// gradient(at: Float(4), in: cubed)
// gradient(at: Float(4), of: cubed)
```

> TODO: Update the \[differentiable\] attribute directly above the Swift declaration of `cubed(_:)` with a SIL differentiability witness.
Expand Down