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// RUN: %target-run-simple-swift
// REQUIRES: executable_test
import _Differentiation
import StdlibUnittest
var TypeErasureTests = TestSuite("DifferentiableTypeErasure")
struct Vector: Differentiable, Equatable {
var x, y: Float
}
struct Generic<T: Differentiable & Equatable>: Differentiable, Equatable {
var x: T
}
extension AnyDerivative {
// This exists only to facilitate testing.
func moved(along offset: TangentVector) -> Self {
var result = self
result.move(by: offset)
return result
}
}
TypeErasureTests.test("AnyDifferentiable operations") {
do {
var any = AnyDifferentiable(Vector(x: 1, y: 1))
let tan = AnyDerivative(Vector.TangentVector(x: 1, y: 1))
any.move(by: tan)
expectEqual(Vector(x: 2, y: 2), any.base as? Vector)
}
do {
var any = AnyDifferentiable(Generic<Float>(x: 1))
let tan = AnyDerivative(Generic<Float>.TangentVector(x: 1))
any.move(by: tan)
expectEqual(Generic<Float>(x: 2), any.base as? Generic<Float>)
}
}
TypeErasureTests.test("AnyDerivative operations") {
do {
var tan = AnyDerivative(Vector.TangentVector(x: 1, y: 1))
tan += tan
expectEqual(AnyDerivative(Vector.TangentVector(x: 2, y: 2)), tan)
expectEqual(AnyDerivative(Vector.TangentVector(x: 4, y: 4)), tan + tan)
expectEqual(AnyDerivative(Vector.TangentVector(x: 0, y: 0)), tan - tan)
expectEqual(AnyDerivative(Vector.TangentVector(x: 4, y: 4)), tan.moved(along: tan))
expectEqual(AnyDerivative(Vector.TangentVector(x: 2, y: 2)), tan)
}
do {
var tan = AnyDerivative(Generic<Float>.TangentVector(x: 1))
tan += tan
expectEqual(AnyDerivative(Generic<Float>.TangentVector(x: 2)), tan)
expectEqual(AnyDerivative(Generic<Float>.TangentVector(x: 4)), tan + tan)
expectEqual(AnyDerivative(Generic<Float>.TangentVector(x: 0)), tan - tan)
expectEqual(AnyDerivative(Generic<Float>.TangentVector(x: 4)), tan.moved(along: tan))
}
}
TypeErasureTests.test("AnyDerivative.zero") {
var zero = AnyDerivative.zero
zero += zero
zero -= zero
expectEqual(zero, zero + zero)
expectEqual(zero, zero - zero)
expectEqual(zero, zero.moved(along: zero))
var tan = AnyDerivative(Vector.TangentVector(x: 1, y: 1))
expectEqual(zero, zero)
expectEqual(AnyDerivative(Vector.TangentVector.zero), tan - tan)
expectNotEqual(AnyDerivative(Vector.TangentVector.zero), zero)
expectNotEqual(AnyDerivative.zero, tan - tan)
tan += zero
tan -= zero
expectEqual(tan, tan + zero)
expectEqual(tan, tan - zero)
expectEqual(tan, tan.moved(along: zero))
expectEqual(tan, zero.moved(along: tan))
expectEqual(zero, zero)
expectEqual(tan, tan)
}
TypeErasureTests.test("AnyDifferentiable casting") {
let any = AnyDifferentiable(Vector(x: 1, y: 1))
expectEqual(Vector(x: 1, y: 1), any.base as? Vector)
let genericAny = AnyDifferentiable(Generic<Float>(x: 1))
expectEqual(Generic<Float>(x: 1),
genericAny.base as? Generic<Float>)
expectEqual(nil, genericAny.base as? Generic<Double>)
}
TypeErasureTests.test("AnyDifferentiable reflection") {
let originalVector = Vector(x: 1, y: 1)
let vector = AnyDifferentiable(originalVector)
let mirror = Mirror(reflecting: vector)
let children = Array(mirror.children)
expectEqual(2, children.count)
expectEqual(["x", "y"], children.map(\.label))
expectEqual([originalVector.x, originalVector.y], children.map { $0.value as! Float })
}
TypeErasureTests.test("AnyDerivative casting") {
let tan = AnyDerivative(Vector.TangentVector(x: 1, y: 1))
expectEqual(Vector.TangentVector(x: 1, y: 1), tan.base as? Vector.TangentVector)
let genericTan = AnyDerivative(Generic<Float>.TangentVector(x: 1))
expectEqual(Generic<Float>.TangentVector(x: 1),
genericTan.base as? Generic<Float>.TangentVector)
expectEqual(nil, genericTan.base as? Generic<Double>.TangentVector)
let zero = AnyDerivative.zero
expectEqual(nil, zero.base as? Float)
expectEqual(nil, zero.base as? Vector.TangentVector)
expectEqual(nil, zero.base as? Generic<Float>.TangentVector)
}
TypeErasureTests.test("AnyDerivative reflection") {
let originalTan = Vector.TangentVector(x: 1, y: 1)
let tan = AnyDerivative(originalTan)
let mirror = Mirror(reflecting: tan)
let children = Array(mirror.children)
expectEqual(2, children.count)
expectEqual(["x", "y"], children.map(\.label))
expectEqual([originalTan.x, originalTan.y], children.map { $0.value as! Float })
}
TypeErasureTests.test("AnyDifferentiable differentiation") {
// Test `AnyDifferentiable` initializer.
do {
let x: Float = 3
let v = AnyDerivative(Float(2))
let 𝛁x = pullback(at: x, of: { AnyDifferentiable($0) })(v)
let expectedVJP: Float = 2
expectEqual(expectedVJP, 𝛁x)
}
do {
let x = Vector(x: 4, y: 5)
let v = AnyDerivative(Vector.TangentVector(x: 2, y: 2))
let 𝛁x = pullback(at: x, of: { AnyDifferentiable($0) })(v)
let expectedVJP = Vector.TangentVector(x: 2, y: 2)
expectEqual(expectedVJP, 𝛁x)
}
do {
let x = Generic<Double>(x: 4)
let v = AnyDerivative(Generic<Double>.TangentVector(x: 2))
let 𝛁x = pullback(at: x, of: { AnyDifferentiable($0) })(v)
let expectedVJP = Generic<Double>.TangentVector(x: 2)
expectEqual(expectedVJP, 𝛁x)
}
}
TypeErasureTests.test("AnyDerivative differentiation") {
// Test `AnyDerivative` operations.
func tripleSum(_ x: AnyDerivative, _ y: AnyDerivative) -> AnyDerivative {
let sum = x + y
return sum + sum + sum
}
do {
let x = AnyDerivative(Float(4))
let y = AnyDerivative(Float(-2))
let v = AnyDerivative(Float(1))
let expectedVJP: Float = 3
let (𝛁x, 𝛁y) = pullback(at: x, y, of: tripleSum)(v)
expectEqual(expectedVJP, 𝛁x.base as? Float)
expectEqual(expectedVJP, 𝛁y.base as? Float)
}
do {
let x = AnyDerivative(Vector.TangentVector(x: 4, y: 5))
let y = AnyDerivative(Vector.TangentVector(x: -2, y: -1))
let v = AnyDerivative(Vector.TangentVector(x: 1, y: 1))
let expectedVJP = Vector.TangentVector(x: 3, y: 3)
let (𝛁x, 𝛁y) = pullback(at: x, y, of: tripleSum)(v)
expectEqual(expectedVJP, 𝛁x.base as? Vector.TangentVector)
expectEqual(expectedVJP, 𝛁y.base as? Vector.TangentVector)
}
do {
let x = AnyDerivative(Generic<Double>.TangentVector(x: 4))
let y = AnyDerivative(Generic<Double>.TangentVector(x: -2))
let v = AnyDerivative(Generic<Double>.TangentVector(x: 1))
let expectedVJP = Generic<Double>.TangentVector(x: 3)
let (𝛁x, 𝛁y) = pullback(at: x, y, of: tripleSum)(v)
expectEqual(expectedVJP, 𝛁x.base as? Generic<Double>.TangentVector)
expectEqual(expectedVJP, 𝛁y.base as? Generic<Double>.TangentVector)
}
// Test `AnyDerivative` initializer.
func typeErased<T>(_ x: T) -> AnyDerivative
where T: Differentiable, T.TangentVector == T {
let any = AnyDerivative(x)
return any + any
}
do {
let x: Float = 3
let v = AnyDerivative(Float(1))
let 𝛁x = pullback(at: x, of: { x in typeErased(x) })(v)
let expectedVJP: Float = 2
expectEqual(expectedVJP, 𝛁x)
}
do {
let x = Vector.TangentVector(x: 4, y: 5)
let v = AnyDerivative(Vector.TangentVector(x: 1, y: 1))
let 𝛁x = pullback(at: x, of: { x in typeErased(x) })(v)
let expectedVJP = Vector.TangentVector(x: 2, y: 2)
expectEqual(expectedVJP, 𝛁x)
}
do {
let x = Generic<Double>.TangentVector(x: 4)
let v = AnyDerivative(Generic<Double>.TangentVector(x: 1))
let 𝛁x = pullback(at: x, of: { x in typeErased(x) })(v)
let expectedVJP = Generic<Double>.TangentVector(x: 2)
expectEqual(expectedVJP, 𝛁x)
}
}
runAllTests()
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