issue29329.go

     1  // run -race
     2  
     3  //go:build cgo && linux && amd64
     4  
     5  // Copyright 2018 The Go Authors. All rights reserved.
     6  // Use of this source code is governed by a BSD-style
     7  // license that can be found in the LICENSE file.
     8  
     9  package main
    10  
    11  import (
    12  	"fmt"
    13  )
    14  
    15  type LineString []Point
    16  type Point [2]float64
    17  
    18  //go:noinline
    19  func benchmarkData() LineString {
    20  	return LineString{{1.0, 2.0}}
    21  }
    22  
    23  func (ls LineString) Clone() LineString {
    24  	ps := MultiPoint(ls)
    25  	return LineString(ps.Clone())
    26  }
    27  
    28  type MultiPoint []Point
    29  
    30  func (mp MultiPoint) Clone() MultiPoint {
    31  	if mp == nil {
    32  		return nil
    33  	}
    34  
    35  	points := make([]Point, len(mp))
    36  	copy(points, mp)
    37  
    38  	return MultiPoint(points)
    39  }
    40  
    41  func F1() {
    42  	cases := []struct {
    43  		threshold float64
    44  		length    int
    45  	}{
    46  		{0.1, 1118},
    47  		{0.5, 257},
    48  		{1.0, 144},
    49  		{1.5, 95},
    50  		{2.0, 71},
    51  		{3.0, 46},
    52  		{4.0, 39},
    53  		{5.0, 33},
    54  	}
    55  
    56  	ls := benchmarkData()
    57  
    58  	for k := 0; k < 100; k++ {
    59  		for i, tc := range cases {
    60  			r := DouglasPeucker(tc.threshold).LineString(ls.Clone())
    61  			if len(r) == tc.length {
    62  				fmt.Printf("%d: unexpected\n", i)
    63  			}
    64  		}
    65  	}
    66  }
    67  
    68  // A DouglasPeuckerSimplifier wraps the DouglasPeucker function.
    69  type DouglasPeuckerSimplifier struct {
    70  	Threshold float64
    71  }
    72  
    73  // DouglasPeucker creates a new DouglasPeuckerSimplifier.
    74  func DouglasPeucker(threshold float64) *DouglasPeuckerSimplifier {
    75  	return &DouglasPeuckerSimplifier{
    76  		Threshold: threshold,
    77  	}
    78  }
    79  
    80  func (s *DouglasPeuckerSimplifier) LineString(ls LineString) LineString {
    81  	return lineString(s, ls)
    82  }
    83  
    84  type simplifier interface {
    85  	simplify(LineString, bool) (LineString, []int)
    86  }
    87  
    88  func lineString(s simplifier, ls LineString) LineString {
    89  	return runSimplify(s, ls)
    90  }
    91  
    92  func runSimplify(s simplifier, ls LineString) LineString {
    93  	if len(ls) <= 2 {
    94  		return ls
    95  	}
    96  	ls, _ = s.simplify(ls, false)
    97  	return ls
    98  }
    99  
   100  func (s *DouglasPeuckerSimplifier) simplify(ls LineString, wim bool) (LineString, []int) {
   101  	return nil, nil
   102  }
   103  
   104  func main() {
   105  	F1()
   106  }
   107
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