libgo/go/sort/search_test.go

   1 // Copyright 2010 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 package sort_test
   6
   7 import (
   8         "runtime"
   9         . "sort"
  10         "testing"
  11 )
  12
  13 func f(a []int, x int) func(int) bool {
  14         return func(i int) bool {
  15                 return a[i] >= x
  16         }
  17 }
  18
  19 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}
  20
  21 var tests = []struct {
  22         name string
  23         n    int
  24         f    func(int) bool
  25         i    int
  26 }{
  27         {"empty", 0, nil, 0},
  28         {"1 1", 1, func(i int) bool { return i >= 1 }, 1},
  29         {"1 true", 1, func(i int) bool { return true }, 0},
  30         {"1 false", 1, func(i int) bool { return false }, 1},
  31         {"1e9 991", 1e9, func(i int) bool { return i >= 991 }, 991},
  32         {"1e9 true", 1e9, func(i int) bool { return true }, 0},
  33         {"1e9 false", 1e9, func(i int) bool { return false }, 1e9},
  34         {"data -20", len(data), f(data, -20), 0},
  35         {"data -10", len(data), f(data, -10), 0},
  36         {"data -9", len(data), f(data, -9), 1},
  37         {"data -6", len(data), f(data, -6), 1},
  38         {"data -5", len(data), f(data, -5), 1},
  39         {"data 3", len(data), f(data, 3), 5},
  40         {"data 11", len(data), f(data, 11), 8},
  41         {"data 99", len(data), f(data, 99), 9},
  42         {"data 100", len(data), f(data, 100), 9},
  43         {"data 101", len(data), f(data, 101), 12},
  44         {"data 10000", len(data), f(data, 10000), 13},
  45         {"data 10001", len(data), f(data, 10001), 14},
  46         {"descending a", 7, func(i int) bool { return []int{99, 99, 59, 42, 7, 0, -1, -1}[i] <= 7 }, 4},
  47         {"descending 7", 1e9, func(i int) bool { return 1e9-i <= 7 }, 1e9 - 7},
  48         {"overflow", 2e9, func(i int) bool { return false }, 2e9},
  49 }
  50
  51 func TestSearch(t *testing.T) {
  52         for _, e := range tests {
  53                 i := Search(e.n, e.f)
  54                 if i != e.i {
  55                         t.Errorf("%s: expected index %d; got %d", e.name, e.i, i)
  56                 }
  57         }
  58 }
  59
  60 // log2 computes the binary logarithm of x, rounded up to the next integer.
  61 // (log2(0) == 0, log2(1) == 0, log2(2) == 1, log2(3) == 2, etc.)
  62 //
  63 func log2(x int) int {
  64         n := 0
  65         for p := 1; p < x; p += p {
  66                 // p == 2**n
  67                 n++
  68         }
  69         // p/2 < x <= p == 2**n
  70         return n
  71 }
  72
  73 func TestSearchEfficiency(t *testing.T) {
  74         n := 100
  75         step := 1
  76         for exp := 2; exp < 10; exp++ {
  77                 // n == 10**exp
  78                 // step == 10**(exp-2)
  79                 max := log2(n)
  80                 for x := 0; x < n; x += step {
  81                         count := 0
  82                         i := Search(n, func(i int) bool { count++; return i >= x })
  83                         if i != x {
  84                                 t.Errorf("n = %d: expected index %d; got %d", n, x, i)
  85                         }
  86                         if count > max {
  87                                 t.Errorf("n = %d, x = %d: expected <= %d calls; got %d", n, x, max, count)
  88                         }
  89                 }
  90                 n *= 10
  91                 step *= 10
  92         }
  93 }
  94
  95 // Smoke tests for convenience wrappers - not comprehensive.
  96
  97 var fdata = []float64{0: -3.14, 1: 0, 2: 1, 3: 2, 4: 1000.7}
  98 var sdata = []string{0: "f", 1: "foo", 2: "foobar", 3: "x"}
  99
 100 var wrappertests = []struct {
 101         name   string
 102         result int
 103         i      int
 104 }{
 105         {"SearchInts", SearchInts(data, 11), 8},
 106         {"SearchFloat64s", SearchFloat64s(fdata, 2.1), 4},
 107         {"SearchStrings", SearchStrings(sdata, ""), 0},
 108         {"IntSlice.Search", IntSlice(data).Search(0), 2},
 109         {"Float64Slice.Search", Float64Slice(fdata).Search(2.0), 3},
 110         {"StringSlice.Search", StringSlice(sdata).Search("x"), 3},
 111 }
 112
 113 func TestSearchWrappers(t *testing.T) {
 114         for _, e := range wrappertests {
 115                 if e.result != e.i {
 116                         t.Errorf("%s: expected index %d; got %d", e.name, e.i, e.result)
 117                 }
 118         }
 119 }
 120
 121 func runSearchWrappers() {
 122         SearchInts(data, 11)
 123         SearchFloat64s(fdata, 2.1)
 124         SearchStrings(sdata, "")
 125         IntSlice(data).Search(0)
 126         Float64Slice(fdata).Search(2.0)
 127         StringSlice(sdata).Search("x")
 128 }
 129
 130 func TestSearchWrappersDontAlloc(t *testing.T) {
 131         if runtime.GOMAXPROCS(0) > 1 {
 132                 t.Skip("skipping; GOMAXPROCS>1")
 133         }
 134         t.Skip("skipping alloc test for gccgo")
 135         allocs := testing.AllocsPerRun(100, runSearchWrappers)
 136         if allocs != 0 {
 137                 t.Errorf("expected no allocs for runSearchWrappers, got %v", allocs)
 138         }
 139 }
 140
 141 func BenchmarkSearchWrappers(b *testing.B) {
 142         for i := 0; i < b.N; i++ {
 143                 runSearchWrappers()
 144         }
 145 }
 146
 147 // Abstract exhaustive test: all sizes up to 100,
 148 // all possible return values.  If there are any small
 149 // corner cases, this test exercises them.
 150 func TestSearchExhaustive(t *testing.T) {
 151         for size := 0; size <= 100; size++ {
 152                 for targ := 0; targ <= size; targ++ {
 153                         i := Search(size, func(i int) bool { return i >= targ })
 154                         if i != targ {
 155                                 t.Errorf("Search(%d, %d) = %d", size, targ, i)
 156                         }
 157                 }
 158         }
 159 }