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83 lines
1.8 KiB
Go
83 lines
1.8 KiB
Go
// Copyright ©2016 The gonum Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package integrate
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import (
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"math"
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"testing"
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"gonum.org/v1/gonum/floats"
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)
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func TestTrapezoidal(t *testing.T) {
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const N = 1e6
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x := floats.Span(make([]float64, N), 0, 1)
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for i, test := range []struct {
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x []float64
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f func(x float64) float64
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want float64
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}{
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{
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x: x,
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f: func(x float64) float64 { return x },
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want: 0.5,
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},
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{
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x: floats.Span(make([]float64, N), -1, 1),
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f: func(x float64) float64 { return x },
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want: 0,
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},
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{
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x: x,
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f: func(x float64) float64 { return x + 10 },
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want: 10.5,
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},
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{
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x: x,
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f: func(x float64) float64 { return 3*x*x + 10 },
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want: 11,
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},
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{
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x: x,
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f: func(x float64) float64 { return math.Exp(x) },
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want: 1.7182818284591876,
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},
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{
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x: floats.Span(make([]float64, N), 0, math.Pi),
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f: func(x float64) float64 { return math.Cos(x) },
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want: 0,
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},
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{
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x: floats.Span(make([]float64, N), 0, 2*math.Pi),
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f: func(x float64) float64 { return math.Cos(x) },
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want: 0,
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},
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{
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x: floats.Span(make([]float64, N*10), 0, math.Pi),
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f: func(x float64) float64 { return math.Sin(x) },
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want: 2,
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},
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{
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x: floats.Span(make([]float64, N*10), 0, 0.5*math.Pi),
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f: func(x float64) float64 { return math.Sin(x) },
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want: 1,
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},
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{
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x: floats.Span(make([]float64, N), 0, 2*math.Pi),
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f: func(x float64) float64 { return math.Sin(x) },
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want: 0,
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},
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} {
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y := make([]float64, len(test.x))
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for i, v := range test.x {
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y[i] = test.f(v)
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}
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v := Trapezoidal(test.x, y)
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if !floats.EqualWithinAbs(v, test.want, 1e-12) {
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t.Errorf("test #%d: got=%v want=%v\n", i, v, test.want)
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}
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}
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}
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