1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
|
// Copyright 2010 The Go 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 sort
import "testing"
func f(a []int, x int) func(int) bool {
return func(i int) bool {
return a[i] >= x
}
}
var data = []int{0: -10, 1: -5, 2: 0, 3: 1, 4: 2, 5: 3, 6: 5, 7: 7, 8: 11, 9: 100, 10: 100, 11: 100, 12: 1000, 13: 10000}
var tests = []struct {
name string
n int
f func(int) bool
i int
}{
{"empty", 0, nil, 0},
{"1 1", 1, func(i int) bool { return i >= 1 }, 1},
{"1 true", 1, func(i int) bool { return true }, 0},
{"1 false", 1, func(i int) bool { return false }, 1},
{"1e9 991", 1e9, func(i int) bool { return i >= 991 }, 991},
{"1e9 true", 1e9, func(i int) bool { return true }, 0},
{"1e9 false", 1e9, func(i int) bool { return false }, 1e9},
{"data -20", len(data), f(data, -20), 0},
{"data -10", len(data), f(data, -10), 0},
{"data -9", len(data), f(data, -9), 1},
{"data -6", len(data), f(data, -6), 1},
{"data -5", len(data), f(data, -5), 1},
{"data 3", len(data), f(data, 3), 5},
{"data 11", len(data), f(data, 11), 8},
{"data 99", len(data), f(data, 99), 9},
{"data 100", len(data), f(data, 100), 9},
{"data 101", len(data), f(data, 101), 12},
{"data 10000", len(data), f(data, 10000), 13},
{"data 10001", len(data), f(data, 10001), 14},
{"descending a", 7, func(i int) bool { return []int{99, 99, 59, 42, 7, 0, -1, -1}[i] <= 7 }, 4},
{"descending 7", 1e9, func(i int) bool { return 1e9-i <= 7 }, 1e9 - 7},
{"overflow", 2e9, func(i int) bool { return false }, 2e9},
}
func TestSearch(t *testing.T) {
for _, e := range tests {
i := Search(e.n, e.f)
if i != e.i {
t.Errorf("%s: expected index %d; got %d", e.name, e.i, i)
}
}
}
// log2 computes the binary logarithm of x, rounded up to the next integer.
// (log2(0) == 0, log2(1) == 0, log2(2) == 1, log2(3) == 2, etc.)
//
func log2(x int) int {
n := 0
for p := 1; p < x; p += p {
// p == 2**n
n++
}
// p/2 < x <= p == 2**n
return n
}
func TestSearchEfficiency(t *testing.T) {
n := 100
step := 1
for exp := 2; exp < 10; exp++ {
// n == 10**exp
// step == 10**(exp-2)
max := log2(n)
for x := 0; x < n; x += step {
count := 0
i := Search(n, func(i int) bool { count++; return i >= x })
if i != x {
t.Errorf("n = %d: expected index %d; got %d", n, x, i)
}
if count > max {
t.Errorf("n = %d, x = %d: expected <= %d calls; got %d", n, x, max, count)
}
}
n *= 10
step *= 10
}
}
// Smoke tests for convenience wrappers - not comprehensive.
var fdata = []float64{0: -3.14, 1: 0, 2: 1, 3: 2, 4: 1000.7}
var sdata = []string{0: "f", 1: "foo", 2: "foobar", 3: "x"}
var wrappertests = []struct {
name string
result int
i int
}{
{"SearchInts", SearchInts(data, 11), 8},
{"SearchFloat64s", SearchFloat64s(fdata, 2.1), 4},
{"SearchStrings", SearchStrings(sdata, ""), 0},
{"IntArray.Search", IntArray(data).Search(0), 2},
{"Float64Array.Search", Float64Array(fdata).Search(2.0), 3},
{"StringArray.Search", StringArray(sdata).Search("x"), 3},
}
func TestSearchWrappers(t *testing.T) {
for _, e := range wrappertests {
if e.result != e.i {
t.Errorf("%s: expected index %d; got %d", e.name, e.i, e.result)
}
}
}
// Abstract exhaustive test: all sizes up to 100,
// all possible return values. If there are any small
// corner cases, this test exercises them.
func TestSearchExhaustive(t *testing.T) {
for size := 0; size <= 100; size++ {
for targ := 0; targ <= size; targ++ {
i := Search(size, func(i int) bool { return i >= targ })
if i != targ {
t.Errorf("Search(%d, %d) = %d", size, targ, i)
}
}
}
}
|
