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 testing.Short() {
   132  		t.Skip("skipping malloc count in short mode")
   133  	}
   134  	if runtime.GOMAXPROCS(0) > 1 {
   135  		t.Skip("skipping; GOMAXPROCS>1")
   136  	}
   137  	allocs := testing.AllocsPerRun(100, runSearchWrappers)
   138  	if allocs != 0 {
   139  		t.Errorf("expected no allocs for runSearchWrappers, got %v", allocs)
   140  	}
   141  }
   142  
   143  func BenchmarkSearchWrappers(b *testing.B) {
   144  	for i := 0; i < b.N; i++ {
   145  		runSearchWrappers()
   146  	}
   147  }
   148  
   149  // Abstract exhaustive test: all sizes up to 100,
   150  // all possible return values. If there are any small
   151  // corner cases, this test exercises them.
   152  func TestSearchExhaustive(t *testing.T) {
   153  	for size := 0; size <= 100; size++ {
   154  		for targ := 0; targ <= size; targ++ {
   155  			i := Search(size, func(i int) bool { return i >= targ })
   156  			if i != targ {
   157  				t.Errorf("Search(%d, %d) = %d", size, targ, i)
   158  			}
   159  		}
   160  	}
   161  }
   162
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