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         . "sort"
   9         "testing"
  10 )
  11
  12 func f(a []int, x int) func(int) bool {
  13         return func(i int) bool {
  14                 return a[i] >= x
  15         }
  16 }
  17
  18 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}
  19
  20 var tests = []struct {
  21         name string
  22         n    int
  23         f    func(int) bool
  24         i    int
  25 }{
  26         {"empty", 0, nil, 0},
  27         {"1 1", 1, func(i int) bool { return i >= 1 }, 1},
  28         {"1 true", 1, func(i int) bool { return true }, 0},
  29         {"1 false", 1, func(i int) bool { return false }, 1},
  30         {"1e9 991", 1e9, func(i int) bool { return i >= 991 }, 991},
  31         {"1e9 true", 1e9, func(i int) bool { return true }, 0},
  32         {"1e9 false", 1e9, func(i int) bool { return false }, 1e9},
  33         {"data -20", len(data), f(data, -20), 0},
  34         {"data -10", len(data), f(data, -10), 0},
  35         {"data -9", len(data), f(data, -9), 1},
  36         {"data -6", len(data), f(data, -6), 1},
  37         {"data -5", len(data), f(data, -5), 1},
  38         {"data 3", len(data), f(data, 3), 5},
  39         {"data 11", len(data), f(data, 11), 8},
  40         {"data 99", len(data), f(data, 99), 9},
  41         {"data 100", len(data), f(data, 100), 9},
  42         {"data 101", len(data), f(data, 101), 12},
  43         {"data 10000", len(data), f(data, 10000), 13},
  44         {"data 10001", len(data), f(data, 10001), 14},
  45         {"descending a", 7, func(i int) bool { return []int{99, 99, 59, 42, 7, 0, -1, -1}[i] <= 7 }, 4},
  46         {"descending 7", 1e9, func(i int) bool { return 1e9-i <= 7 }, 1e9 - 7},
  47         {"overflow", 2e9, func(i int) bool { return false }, 2e9},
  48 }
  49
  50 func TestSearch(t *testing.T) {
  51         for _, e := range tests {
  52                 i := Search(e.n, e.f)
  53                 if i != e.i {
  54                         t.Errorf("%s: expected index %d; got %d", e.name, e.i, i)
  55                 }
  56         }
  57 }
  58
  59 // log2 computes the binary logarithm of x, rounded up to the next integer.
  60 // (log2(0) == 0, log2(1) == 0, log2(2) == 1, log2(3) == 2, etc.)
  61 //
  62 func log2(x int) int {
  63         n := 0
  64         for p := 1; p < x; p += p {
  65                 // p == 2**n
  66                 n++
  67         }
  68         // p/2 < x <= p == 2**n
  69         return n
  70 }
  71
  72 func TestSearchEfficiency(t *testing.T) {
  73         n := 100
  74         step := 1
  75         for exp := 2; exp < 10; exp++ {
  76                 // n == 10**exp
  77                 // step == 10**(exp-2)
  78                 max := log2(n)
  79                 for x := 0; x < n; x += step {
  80                         count := 0
  81                         i := Search(n, func(i int) bool { count++; return i >= x })
  82                         if i != x {
  83                                 t.Errorf("n = %d: expected index %d; got %d", n, x, i)
  84                         }
  85                         if count > max {
  86                                 t.Errorf("n = %d, x = %d: expected <= %d calls; got %d", n, x, max, count)
  87                         }
  88                 }
  89                 n *= 10
  90                 step *= 10
  91         }
  92 }
  93
  94 // Smoke tests for convenience wrappers - not comprehensive.
  95
  96 var fdata = []float64{0: -3.14, 1: 0, 2: 1, 3: 2, 4: 1000.7}
  97 var sdata = []string{0: "f", 1: "foo", 2: "foobar", 3: "x"}
  98
  99 var wrappertests = []struct {
 100         name   string
 101         result int
 102         i      int
 103 }{
 104         {"SearchInts", SearchInts(data, 11), 8},
 105         {"SearchFloat64s", SearchFloat64s(fdata, 2.1), 4},
 106         {"SearchStrings", SearchStrings(sdata, ""), 0},
 107         {"IntSlice.Search", IntSlice(data).Search(0), 2},
 108         {"Float64Slice.Search", Float64Slice(fdata).Search(2.0), 3},
 109         {"StringSlice.Search", StringSlice(sdata).Search("x"), 3},
 110 }
 111
 112 func TestSearchWrappers(t *testing.T) {
 113         for _, e := range wrappertests {
 114                 if e.result != e.i {
 115                         t.Errorf("%s: expected index %d; got %d", e.name, e.i, e.result)
 116                 }
 117         }
 118 }
 119
 120 // Abstract exhaustive test: all sizes up to 100,
 121 // all possible return values.  If there are any small
 122 // corner cases, this test exercises them.
 123 func TestSearchExhaustive(t *testing.T) {
 124         for size := 0; size <= 100; size++ {
 125                 for targ := 0; targ <= size; targ++ {
 126                         i := Search(size, func(i int) bool { return i >= targ })
 127                         if i != targ {
 128                                 t.Errorf("Search(%d, %d) = %d", size, targ, i)
 129                         }
 130                 }
 131         }
 132 }