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// Copyright ©2014 The Gonum Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package fd
import (
"math"
"testing"
)
var xSquared = func(x float64) float64 { return x * x }
type testPoint struct {
f func(float64) float64
loc float64
fofx float64
ans float64
}
var testsFirst = []testPoint{
{
f: xSquared,
loc: 0,
fofx: 0,
ans: 0,
},
{
f: xSquared,
loc: 5,
fofx: 25,
ans: 10,
},
{
f: xSquared,
loc: 2,
fofx: 4,
ans: 4,
},
{
f: xSquared,
loc: -5,
fofx: 25,
ans: -10,
},
}
var testsSecond = []testPoint{
{
f: xSquared,
loc: 0,
fofx: 0,
ans: 2,
},
{
f: xSquared,
loc: 5,
fofx: 25,
ans: 2,
},
{
f: xSquared,
loc: 2,
fofx: 4,
ans: 2,
},
{
f: xSquared,
loc: -5,
fofx: 25,
ans: 2,
},
}
func testDerivative(t *testing.T, formula Formula, tol float64, tests []testPoint) {
for i, test := range tests {
ans := Derivative(test.f, test.loc, &Settings{
Formula: formula,
})
if math.Abs(test.ans-ans) > tol {
t.Errorf("Case %v: ans mismatch serial: expected %v, found %v", i, test.ans, ans)
}
ans = Derivative(test.f, test.loc, &Settings{
Formula: formula,
OriginKnown: true,
OriginValue: test.fofx,
})
if math.Abs(test.ans-ans) > tol {
t.Errorf("Case %v: ans mismatch serial origin known: expected %v, found %v", i, test.ans, ans)
}
ans = Derivative(test.f, test.loc, &Settings{
Formula: formula,
Concurrent: true,
})
if math.Abs(test.ans-ans) > tol {
t.Errorf("Case %v: ans mismatch concurrent: expected %v, found %v", i, test.ans, ans)
}
ans = Derivative(test.f, test.loc, &Settings{
Formula: formula,
OriginKnown: true,
OriginValue: test.fofx,
Concurrent: true,
})
if math.Abs(test.ans-ans) > tol {
t.Errorf("Case %v: ans mismatch concurrent: expected %v, found %v", i, test.ans, ans)
}
}
}
func TestForward(t *testing.T) {
t.Parallel()
testDerivative(t, Forward, 2e-4, testsFirst)
}
func TestBackward(t *testing.T) {
t.Parallel()
testDerivative(t, Backward, 2e-4, testsFirst)
}
func TestCentral(t *testing.T) {
t.Parallel()
testDerivative(t, Central, 1e-6, testsFirst)
}
func TestCentralSecond(t *testing.T) {
t.Parallel()
testDerivative(t, Central2nd, 1e-3, testsSecond)
}
// TestDerivativeDefault checks that the derivative works when settings is nil
// or zero value.
func TestDerivativeDefault(t *testing.T) {
t.Parallel()
tol := 1e-6
for i, test := range testsFirst {
ans := Derivative(test.f, test.loc, nil)
if math.Abs(test.ans-ans) > tol {
t.Errorf("Case %v: ans mismatch default: expected %v, found %v", i, test.ans, ans)
}
ans = Derivative(test.f, test.loc, &Settings{})
if math.Abs(test.ans-ans) > tol {
t.Errorf("Case %v: ans mismatch zero value: expected %v, found %v", i, test.ans, ans)
}
}
}
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