commonTest.space.kscience.kmath.expressions.SimpleAutoDiffTest.kt Maven / Gradle / Ivy
package space.kscience.kmath.expressions
import space.kscience.kmath.operations.RealField
import space.kscience.kmath.structures.asBuffer
import kotlin.math.E
import kotlin.math.PI
import kotlin.math.pow
import kotlin.math.sqrt
import kotlin.test.Test
import kotlin.test.assertEquals
import kotlin.test.assertTrue
class SimpleAutoDiffTest {
fun dx(
xBinding: Pair,
body: SimpleAutoDiffField.(x: AutoDiffValue) -> AutoDiffValue,
): DerivationResult = RealField.simpleAutoDiff(xBinding) { body(bindSymbol(xBinding.first)) }
fun dxy(
xBinding: Pair,
yBinding: Pair,
body: SimpleAutoDiffField.(x: AutoDiffValue, y: AutoDiffValue) -> AutoDiffValue,
): DerivationResult = RealField.simpleAutoDiff(xBinding, yBinding) {
body(bindSymbol(xBinding.first), bindSymbol(yBinding.first))
}
fun diff(block: SimpleAutoDiffField.() -> AutoDiffValue): SimpleAutoDiffExpression {
return SimpleAutoDiffExpression(RealField, block)
}
val x by symbol
val y by symbol
val z by symbol
@Test
fun testPlusX2() {
val y = RealField.simpleAutoDiff(x to 3.0) {
// diff w.r.t this x at 3
val x = bindSymbol(x)
x + x
}
assertEquals(6.0, y.value) // y = x + x = 6
assertEquals(2.0, y.derivative(x)) // dy/dx = 2
}
@Test
fun testPlusX2Expr() {
val expr = diff {
val x = bindSymbol(x)
x + x
}
assertEquals(6.0, expr(x to 3.0)) // y = x + x = 6
assertEquals(2.0, expr.derivative(x)(x to 3.0)) // dy/dx = 2
}
@Test
fun testPlus() {
// two variables
val z = RealField.simpleAutoDiff(x to 2.0, y to 3.0) {
val x = bindSymbol(x)
val y = bindSymbol(y)
x + y
}
assertEquals(5.0, z.value) // z = x + y = 5
assertEquals(1.0, z.derivative(x)) // dz/dx = 1
assertEquals(1.0, z.derivative(y)) // dz/dy = 1
}
@Test
fun testMinus() {
// two variables
val z = RealField.simpleAutoDiff(x to 7.0, y to 3.0) {
val x = bindSymbol(x)
val y = bindSymbol(y)
x - y
}
assertEquals(4.0, z.value) // z = x - y = 4
assertEquals(1.0, z.derivative(x)) // dz/dx = 1
assertEquals(-1.0, z.derivative(y)) // dz/dy = -1
}
@Test
fun testMulX2() {
val y = dx(x to 3.0) { x ->
// diff w.r.t this x at 3
x * x
}
assertEquals(9.0, y.value) // y = x * x = 9
assertEquals(6.0, y.derivative(x)) // dy/dx = 2 * x = 7
}
@Test
fun testSqr() {
val y = dx(x to 3.0) { x -> sqr(x) }
assertEquals(9.0, y.value) // y = x ^ 2 = 9
assertEquals(6.0, y.derivative(x)) // dy/dx = 2 * x = 7
}
@Test
fun testSqrSqr() {
val y = dx(x to 2.0) { x -> sqr(sqr(x)) }
assertEquals(16.0, y.value) // y = x ^ 4 = 16
assertEquals(32.0, y.derivative(x)) // dy/dx = 4 * x^3 = 32
}
@Test
fun testX3() {
val y = dx(x to 2.0) { x ->
// diff w.r.t this x at 2
x * x * x
}
assertEquals(8.0, y.value) // y = x * x * x = 8
assertEquals(12.0, y.derivative(x)) // dy/dx = 3 * x * x = 12
}
@Test
fun testDiv() {
val z = dxy(x to 5.0, y to 2.0) { x, y ->
x / y
}
assertEquals(2.5, z.value) // z = x / y = 2.5
assertEquals(0.5, z.derivative(x)) // dz/dx = 1 / y = 0.5
assertEquals(-1.25, z.derivative(y)) // dz/dy = -x / y^2 = -1.25
}
@Test
fun testPow3() {
val y = dx(x to 2.0) { x ->
// diff w.r.t this x at 2
pow(x, 3)
}
assertEquals(8.0, y.value) // y = x ^ 3 = 8
assertEquals(12.0, y.derivative(x)) // dy/dx = 3 * x ^ 2 = 12
}
@Test
fun testPowFull() {
val z = dxy(x to 2.0, y to 3.0) { x, y ->
pow(x, y)
}
assertApprox(8.0, z.value) // z = x ^ y = 8
assertApprox(12.0, z.derivative(x)) // dz/dx = y * x ^ (y - 1) = 12
assertApprox(8.0 * kotlin.math.ln(2.0), z.derivative(y)) // dz/dy = x ^ y * ln(x)
}
@Test
fun testFromPaper() {
val y = dx(x to 3.0) { x -> 2 * x + x * x * x }
assertEquals(33.0, y.value) // y = 2 * x + x * x * x = 33
assertEquals(29.0, y.derivative(x)) // dy/dx = 2 + 3 * x * x = 29
}
@Test
fun testInnerVariable() {
val y = dx(x to 1.0) { x ->
const(1.0) * x
}
assertEquals(1.0, y.value) // y = x ^ n = 1
assertEquals(1.0, y.derivative(x)) // dy/dx = n * x ^ (n - 1) = n - 1
}
@Test
fun testLongChain() {
val n = 10_000
val y = dx(x to 1.0) { x ->
var res = const(1.0)
for (i in 1..n) res *= x
res
}
assertEquals(1.0, y.value) // y = x ^ n = 1
assertEquals(n.toDouble(), y.derivative(x)) // dy/dx = n * x ^ (n - 1) = n - 1
}
@Test
fun testExample() {
val y = dx(x to 2.0) { x -> sqr(x) + 5 * x + 3 }
assertEquals(17.0, y.value) // the value of result (y)
assertEquals(9.0, y.derivative(x)) // dy/dx
}
@Test
fun testSqrt() {
val y = dx(x to 16.0) { x -> sqrt(x) }
assertEquals(4.0, y.value) // y = x ^ 1/2 = 4
assertEquals(1.0 / 8, y.derivative(x)) // dy/dx = 1/2 / x ^ 1/4 = 1/8
}
@Test
fun testSin() {
val y = dx(x to PI / 6.0) { x -> sin(x) }
assertApprox(0.5, y.value) // y = sin(PI/6) = 0.5
assertApprox(sqrt(3.0) / 2, y.derivative(x)) // dy/dx = cos(pi/6) = sqrt(3)/2
}
@Test
fun testCos() {
val y = dx(x to PI / 6) { x -> cos(x) }
assertApprox(sqrt(3.0) / 2, y.value) //y = cos(pi/6) = sqrt(3)/2
assertApprox(-0.5, y.derivative(x)) // dy/dx = -sin(pi/6) = -0.5
}
@Test
fun testTan() {
val y = dx(x to PI / 6) { x -> tan(x) }
assertApprox(1.0 / sqrt(3.0), y.value) // y = tan(pi/6) = 1/sqrt(3)
assertApprox(4.0 / 3.0, y.derivative(x)) // dy/dx = sec(pi/6)^2 = 4/3
}
@Test
fun testAsin() {
val y = dx(x to PI / 6) { x -> asin(x) }
assertApprox(kotlin.math.asin(PI / 6.0), y.value) // y = asin(pi/6)
assertApprox(6.0 / sqrt(36 - PI * PI), y.derivative(x)) // dy/dx = 6/sqrt(36-pi^2)
}
@Test
fun testAcos() {
val y = dx(x to PI / 6) { x -> acos(x) }
assertApprox(kotlin.math.acos(PI / 6.0), y.value) // y = acos(pi/6)
assertApprox(-6.0 / sqrt(36.0 - PI * PI), y.derivative(x)) // dy/dx = -6/sqrt(36-pi^2)
}
@Test
fun testAtan() {
val y = dx(x to PI / 6) { x -> atan(x) }
assertApprox(kotlin.math.atan(PI / 6.0), y.value) // y = atan(pi/6)
assertApprox(36.0 / (36.0 + PI * PI), y.derivative(x)) // dy/dx = 36/(36+pi^2)
}
@Test
fun testSinh() {
val y = dx(x to 0.0) { x -> sinh(x) }
assertApprox(kotlin.math.sinh(0.0), y.value) // y = sinh(0)
assertApprox(kotlin.math.cosh(0.0), y.derivative(x)) // dy/dx = cosh(0)
}
@Test
fun testCosh() {
val y = dx(x to 0.0) { x -> cosh(x) }
assertApprox(1.0, y.value) //y = cosh(0)
assertApprox(0.0, y.derivative(x)) // dy/dx = sinh(0)
}
@Test
fun testTanh() {
val y = dx(x to 1.0) { x -> tanh(x) }
assertApprox((E * E - 1) / (E * E + 1), y.value) // y = tanh(pi/6)
assertApprox(1.0 / kotlin.math.cosh(1.0).pow(2), y.derivative(x)) // dy/dx = sech(pi/6)^2
}
@Test
fun testAsinh() {
val y = dx(x to PI / 6) { x -> asinh(x) }
assertApprox(kotlin.math.asinh(PI / 6.0), y.value) // y = asinh(pi/6)
assertApprox(6.0 / sqrt(36 + PI * PI), y.derivative(x)) // dy/dx = 6/sqrt(pi^2+36)
}
@Test
fun testAcosh() {
val y = dx(x to PI / 6) { x -> acosh(x) }
assertApprox(kotlin.math.acosh(PI / 6.0), y.value) // y = acosh(pi/6)
assertApprox(-6.0 / sqrt(36.0 - PI * PI), y.derivative(x)) // dy/dx = -6/sqrt(36-pi^2)
}
@Test
fun testAtanh() {
val y = dx(x to PI / 6) { x -> atanh(x) }
assertApprox(kotlin.math.atanh(PI / 6.0), y.value) // y = atanh(pi/6)
assertApprox(-36.0 / (PI * PI - 36.0), y.derivative(x)) // dy/dx = -36/(pi^2-36)
}
@Test
fun testDivGrad() {
val res = dxy(x to 1.0, y to 2.0) { x, y -> x * x + y * y }
assertEquals(6.0, res.div())
assertTrue(res.grad(x, y).contentEquals(doubleArrayOf(2.0, 4.0).asBuffer()))
}
private fun assertApprox(a: Double, b: Double) {
if ((a - b) > 1e-10) assertEquals(a, b)
}
}
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