summaryrefslogtreecommitdiff
path: root/libgo/go/sort
diff options
context:
space:
mode:
authorupstream source tree <ports@midipix.org>2015-03-15 20:14:05 -0400
committerupstream source tree <ports@midipix.org>2015-03-15 20:14:05 -0400
commit554fd8c5195424bdbcabf5de30fdc183aba391bd (patch)
tree976dc5ab7fddf506dadce60ae936f43f58787092 /libgo/go/sort
downloadcbb-gcc-4.6.4-554fd8c5195424bdbcabf5de30fdc183aba391bd.tar.bz2
cbb-gcc-4.6.4-554fd8c5195424bdbcabf5de30fdc183aba391bd.tar.xz
obtained gcc-4.6.4.tar.bz2 from upstream website;upstream
verified gcc-4.6.4.tar.bz2.sig; imported gcc-4.6.4 source tree from verified upstream tarball. downloading a git-generated archive based on the 'upstream' tag should provide you with a source tree that is binary identical to the one extracted from the above tarball. if you have obtained the source via the command 'git clone', however, do note that line-endings of files in your working directory might differ from line-endings of the respective files in the upstream repository.
Diffstat (limited to 'libgo/go/sort')
-rw-r--r--libgo/go/sort/search.go110
-rw-r--r--libgo/go/sort/search_test.go137
-rw-r--r--libgo/go/sort/sort.go206
-rw-r--r--libgo/go/sort/sort_test.go267
4 files changed, 720 insertions, 0 deletions
diff --git a/libgo/go/sort/search.go b/libgo/go/sort/search.go
new file mode 100644
index 000000000..6828e19b6
--- /dev/null
+++ b/libgo/go/sort/search.go
@@ -0,0 +1,110 @@
+// 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.
+
+// This file implements binary search.
+
+package sort
+
+// Search uses binary search to find and return the smallest index i
+// in [0, n) at which f(i) is true, assuming that on the range [0, n),
+// f(i) == true implies f(i+1) == true. That is, Search requires that
+// f is false for some (possibly empty) prefix of the input range [0, n)
+// and then true for the (possibly empty) remainder; Search returns
+// the first true index. If there is no such index, Search returns n.
+// Search calls f(i) only for i in the range [0, n).
+//
+// A common use of Search is to find the index i for a value x in
+// a sorted, indexable data structure like an array or slice.
+// In this case, the argument f, typically a closure, captures the value
+// to be searched for, and how the data structure is indexed and
+// ordered.
+//
+// For instance, given a slice data sorted in ascending order,
+// the call Search(len(data), func(i int) bool { return data[i] >= 23 })
+// returns the smallest index i such that data[i] >= 23. If the caller
+// wants to find whether 23 is in the slice, it must test data[i] == 23
+// separately.
+//
+// Searching data sorted in descending order would use the <=
+// operator instead of the >= operator.
+//
+// To complete the example above, the following code tries to find the value
+// x in an integer slice data sorted in ascending order:
+//
+// x := 23
+// i := sort.Search(len(data), func(i int) bool { return data[i] >= x })
+// if i < len(data) && data[i] == x {
+// // x is present at data[i]
+// } else {
+// // x is not present in data,
+// // but i is the index where it would be inserted.
+// }
+//
+// As a more whimsical example, this program guesses your number:
+//
+// func GuessingGame() {
+// var s string
+// fmt.Printf("Pick an integer from 0 to 100.\n")
+// answer := sort.Search(100, func(i int) bool {
+// fmt.Printf("Is your number <= %d? ", i)
+// fmt.Scanf("%s", &s)
+// return s != "" && s[0] == 'y'
+// })
+// fmt.Printf("Your number is %d.\n", answer)
+// }
+//
+func Search(n int, f func(int) bool) int {
+ // Define f(-1) == false and f(n) == true.
+ // Invariant: f(i-1) == false, f(j) == true.
+ i, j := 0, n
+ for i < j {
+ h := i + (j-i)/2 // avoid overflow when computing h
+ // i ≤ h < j
+ if !f(h) {
+ i = h + 1 // preserves f(i-1) == false
+ } else {
+ j = h // preserves f(j) == true
+ }
+ }
+ // i == j, f(i-1) == false, and f(j) (= f(i)) == true => answer is i.
+ return i
+}
+
+
+// Convenience wrappers for common cases.
+
+// SearchInts searches for x in a sorted slice of ints and returns the index
+// as specified by Search. The array must be sorted in ascending order.
+//
+func SearchInts(a []int, x int) int {
+ return Search(len(a), func(i int) bool { return a[i] >= x })
+}
+
+
+// SearchFloat64s searches for x in a sorted slice of float64s and returns the index
+// as specified by Search. The array must be sorted in ascending order.
+//
+func SearchFloat64s(a []float64, x float64) int {
+ return Search(len(a), func(i int) bool { return a[i] >= x })
+}
+
+
+// SearchStrings searches for x in a sorted slice of strings and returns the index
+// as specified by Search. The array must be sorted in ascending order.
+//
+func SearchStrings(a []string, x string) int {
+ return Search(len(a), func(i int) bool { return a[i] >= x })
+}
+
+
+// Search returns the result of applying SearchInts to the receiver and x.
+func (p IntArray) Search(x int) int { return SearchInts(p, x) }
+
+
+// Search returns the result of applying SearchFloat64s to the receiver and x.
+func (p Float64Array) Search(x float64) int { return SearchFloat64s(p, x) }
+
+
+// Search returns the result of applying SearchStrings to the receiver and x.
+func (p StringArray) Search(x string) int { return SearchStrings(p, x) }
diff --git a/libgo/go/sort/search_test.go b/libgo/go/sort/search_test.go
new file mode 100644
index 000000000..939f66af3
--- /dev/null
+++ b/libgo/go/sort/search_test.go
@@ -0,0 +1,137 @@
+// 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)
+ }
+ }
+ }
+}
diff --git a/libgo/go/sort/sort.go b/libgo/go/sort/sort.go
new file mode 100644
index 000000000..c7945d21b
--- /dev/null
+++ b/libgo/go/sort/sort.go
@@ -0,0 +1,206 @@
+// Copyright 2009 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.
+
+// The sort package provides primitives for sorting arrays
+// and user-defined collections.
+package sort
+
+// A type, typically a collection, that satisfies sort.Interface can be
+// sorted by the routines in this package. The methods require that the
+// elements of the collection be enumerated by an integer index.
+type Interface interface {
+ // Len is the number of elements in the collection.
+ Len() int
+ // Less returns whether the element with index i should sort
+ // before the element with index j.
+ Less(i, j int) bool
+ // Swap swaps the elements with indexes i and j.
+ Swap(i, j int)
+}
+
+func min(a, b int) int {
+ if a < b {
+ return a
+ }
+ return b
+}
+
+// Insertion sort
+func insertionSort(data Interface, a, b int) {
+ for i := a + 1; i < b; i++ {
+ for j := i; j > a && data.Less(j, j-1); j-- {
+ data.Swap(j, j-1)
+ }
+ }
+}
+
+// Quicksort, following Bentley and McIlroy,
+// ``Engineering a Sort Function,'' SP&E November 1993.
+
+// Move the median of the three values data[a], data[b], data[c] into data[a].
+func medianOfThree(data Interface, a, b, c int) {
+ m0 := b
+ m1 := a
+ m2 := c
+ // bubble sort on 3 elements
+ if data.Less(m1, m0) {
+ data.Swap(m1, m0)
+ }
+ if data.Less(m2, m1) {
+ data.Swap(m2, m1)
+ }
+ if data.Less(m1, m0) {
+ data.Swap(m1, m0)
+ }
+ // now data[m0] <= data[m1] <= data[m2]
+}
+
+func swapRange(data Interface, a, b, n int) {
+ for i := 0; i < n; i++ {
+ data.Swap(a+i, b+i)
+ }
+}
+
+func doPivot(data Interface, lo, hi int) (midlo, midhi int) {
+ m := lo + (hi-lo)/2 // Written like this to avoid integer overflow.
+ if hi-lo > 40 {
+ // Tukey's ``Ninther,'' median of three medians of three.
+ s := (hi - lo) / 8
+ medianOfThree(data, lo, lo+s, lo+2*s)
+ medianOfThree(data, m, m-s, m+s)
+ medianOfThree(data, hi-1, hi-1-s, hi-1-2*s)
+ }
+ medianOfThree(data, lo, m, hi-1)
+
+ // Invariants are:
+ // data[lo] = pivot (set up by ChoosePivot)
+ // data[lo <= i < a] = pivot
+ // data[a <= i < b] < pivot
+ // data[b <= i < c] is unexamined
+ // data[c <= i < d] > pivot
+ // data[d <= i < hi] = pivot
+ //
+ // Once b meets c, can swap the "= pivot" sections
+ // into the middle of the array.
+ pivot := lo
+ a, b, c, d := lo+1, lo+1, hi, hi
+ for b < c {
+ if data.Less(b, pivot) { // data[b] < pivot
+ b++
+ continue
+ }
+ if !data.Less(pivot, b) { // data[b] = pivot
+ data.Swap(a, b)
+ a++
+ b++
+ continue
+ }
+ if data.Less(pivot, c-1) { // data[c-1] > pivot
+ c--
+ continue
+ }
+ if !data.Less(c-1, pivot) { // data[c-1] = pivot
+ data.Swap(c-1, d-1)
+ c--
+ d--
+ continue
+ }
+ // data[b] > pivot; data[c-1] < pivot
+ data.Swap(b, c-1)
+ b++
+ c--
+ }
+
+ n := min(b-a, a-lo)
+ swapRange(data, lo, b-n, n)
+
+ n = min(hi-d, d-c)
+ swapRange(data, c, hi-n, n)
+
+ return lo + b - a, hi - (d - c)
+}
+
+func quickSort(data Interface, a, b int) {
+ for b-a > 7 {
+ mlo, mhi := doPivot(data, a, b)
+ // Avoiding recursion on the larger subproblem guarantees
+ // a stack depth of at most lg(b-a).
+ if mlo-a < b-mhi {
+ quickSort(data, a, mlo)
+ a = mhi // i.e., quickSort(data, mhi, b)
+ } else {
+ quickSort(data, mhi, b)
+ b = mlo // i.e., quickSort(data, a, mlo)
+ }
+ }
+ if b-a > 1 {
+ insertionSort(data, a, b)
+ }
+}
+
+func Sort(data Interface) { quickSort(data, 0, data.Len()) }
+
+
+func IsSorted(data Interface) bool {
+ n := data.Len()
+ for i := n - 1; i > 0; i-- {
+ if data.Less(i, i-1) {
+ return false
+ }
+ }
+ return true
+}
+
+
+// Convenience types for common cases
+
+// IntArray attaches the methods of Interface to []int, sorting in increasing order.
+type IntArray []int
+
+func (p IntArray) Len() int { return len(p) }
+func (p IntArray) Less(i, j int) bool { return p[i] < p[j] }
+func (p IntArray) Swap(i, j int) { p[i], p[j] = p[j], p[i] }
+
+// Sort is a convenience method.
+func (p IntArray) Sort() { Sort(p) }
+
+
+// Float64Array attaches the methods of Interface to []float64, sorting in increasing order.
+type Float64Array []float64
+
+func (p Float64Array) Len() int { return len(p) }
+func (p Float64Array) Less(i, j int) bool { return p[i] < p[j] }
+func (p Float64Array) Swap(i, j int) { p[i], p[j] = p[j], p[i] }
+
+// Sort is a convenience method.
+func (p Float64Array) Sort() { Sort(p) }
+
+
+// StringArray attaches the methods of Interface to []string, sorting in increasing order.
+type StringArray []string
+
+func (p StringArray) Len() int { return len(p) }
+func (p StringArray) Less(i, j int) bool { return p[i] < p[j] }
+func (p StringArray) Swap(i, j int) { p[i], p[j] = p[j], p[i] }
+
+// Sort is a convenience method.
+func (p StringArray) Sort() { Sort(p) }
+
+
+// Convenience wrappers for common cases
+
+// SortInts sorts an array of ints in increasing order.
+func SortInts(a []int) { Sort(IntArray(a)) }
+// SortFloat64s sorts an array of float64s in increasing order.
+func SortFloat64s(a []float64) { Sort(Float64Array(a)) }
+// SortStrings sorts an array of strings in increasing order.
+func SortStrings(a []string) { Sort(StringArray(a)) }
+
+
+// IntsAreSorted tests whether an array of ints is sorted in increasing order.
+func IntsAreSorted(a []int) bool { return IsSorted(IntArray(a)) }
+// Float64sAreSorted tests whether an array of float64s is sorted in increasing order.
+func Float64sAreSorted(a []float64) bool { return IsSorted(Float64Array(a)) }
+// StringsAreSorted tests whether an array of strings is sorted in increasing order.
+func StringsAreSorted(a []string) bool { return IsSorted(StringArray(a)) }
diff --git a/libgo/go/sort/sort_test.go b/libgo/go/sort/sort_test.go
new file mode 100644
index 000000000..1bea8f032
--- /dev/null
+++ b/libgo/go/sort/sort_test.go
@@ -0,0 +1,267 @@
+// Copyright 2009 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 (
+ "fmt"
+ "rand"
+ "strconv"
+ "testing"
+)
+
+
+var ints = [...]int{74, 59, 238, -784, 9845, 959, 905, 0, 0, 42, 7586, -5467984, 7586}
+var float64s = [...]float64{74.3, 59.0, 238.2, -784.0, 2.3, 9845.768, -959.7485, 905, 7.8, 7.8}
+var strings = [...]string{"", "Hello", "foo", "bar", "foo", "f00", "%*&^*&^&", "***"}
+
+func TestSortIntArray(t *testing.T) {
+ data := ints
+ a := IntArray(data[0:])
+ Sort(a)
+ if !IsSorted(a) {
+ t.Errorf("sorted %v", ints)
+ t.Errorf(" got %v", data)
+ }
+}
+
+func TestSortFloat64Array(t *testing.T) {
+ data := float64s
+ a := Float64Array(data[0:])
+ Sort(a)
+ if !IsSorted(a) {
+ t.Errorf("sorted %v", float64s)
+ t.Errorf(" got %v", data)
+ }
+}
+
+func TestSortStringArray(t *testing.T) {
+ data := strings
+ a := StringArray(data[0:])
+ Sort(a)
+ if !IsSorted(a) {
+ t.Errorf("sorted %v", strings)
+ t.Errorf(" got %v", data)
+ }
+}
+
+func TestSortInts(t *testing.T) {
+ data := ints
+ SortInts(data[0:])
+ if !IntsAreSorted(data[0:]) {
+ t.Errorf("sorted %v", ints)
+ t.Errorf(" got %v", data)
+ }
+}
+
+func TestSortFloat64s(t *testing.T) {
+ data := float64s
+ SortFloat64s(data[0:])
+ if !Float64sAreSorted(data[0:]) {
+ t.Errorf("sorted %v", float64s)
+ t.Errorf(" got %v", data)
+ }
+}
+
+func TestSortStrings(t *testing.T) {
+ data := strings
+ SortStrings(data[0:])
+ if !StringsAreSorted(data[0:]) {
+ t.Errorf("sorted %v", strings)
+ t.Errorf(" got %v", data)
+ }
+}
+
+func TestSortLarge_Random(t *testing.T) {
+ data := make([]int, 1000000)
+ for i := 0; i < len(data); i++ {
+ data[i] = rand.Intn(100)
+ }
+ if IntsAreSorted(data) {
+ t.Fatalf("terrible rand.rand")
+ }
+ SortInts(data)
+ if !IntsAreSorted(data) {
+ t.Errorf("sort didn't sort - 1M ints")
+ }
+}
+
+func BenchmarkSortString1K(b *testing.B) {
+ b.StopTimer()
+ for i := 0; i < b.N; i++ {
+ data := make([]string, 1<<10)
+ for i := 0; i < len(data); i++ {
+ data[i] = strconv.Itoa(i ^ 0x2cc)
+ }
+ b.StartTimer()
+ SortStrings(data)
+ b.StopTimer()
+ }
+}
+
+func BenchmarkSortInt1K(b *testing.B) {
+ b.StopTimer()
+ for i := 0; i < b.N; i++ {
+ data := make([]int, 1<<10)
+ for i := 0; i < len(data); i++ {
+ data[i] = i ^ 0x2cc
+ }
+ b.StartTimer()
+ SortInts(data)
+ b.StopTimer()
+ }
+}
+
+func BenchmarkSortInt64K(b *testing.B) {
+ b.StopTimer()
+ for i := 0; i < b.N; i++ {
+ data := make([]int, 1<<16)
+ for i := 0; i < len(data); i++ {
+ data[i] = i ^ 0xcccc
+ }
+ b.StartTimer()
+ SortInts(data)
+ b.StopTimer()
+ }
+}
+
+const (
+ _Sawtooth = iota
+ _Rand
+ _Stagger
+ _Plateau
+ _Shuffle
+ _NDist
+)
+
+const (
+ _Copy = iota
+ _Reverse
+ _ReverseFirstHalf
+ _ReverseSecondHalf
+ _Sorted
+ _Dither
+ _NMode
+)
+
+type testingData struct {
+ desc string
+ t *testing.T
+ data []int
+ maxswap int // number of swaps allowed
+ nswap int
+}
+
+func (d *testingData) Len() int { return len(d.data) }
+func (d *testingData) Less(i, j int) bool { return d.data[i] < d.data[j] }
+func (d *testingData) Swap(i, j int) {
+ if d.nswap >= d.maxswap {
+ d.t.Errorf("%s: used %d swaps sorting array of %d", d.desc, d.nswap, len(d.data))
+ d.t.FailNow()
+ }
+ d.nswap++
+ d.data[i], d.data[j] = d.data[j], d.data[i]
+}
+
+func lg(n int) int {
+ i := 0
+ for 1<<uint(i) < n {
+ i++
+ }
+ return i
+}
+
+func TestBentleyMcIlroy(t *testing.T) {
+ sizes := []int{100, 1023, 1024, 1025}
+ dists := []string{"sawtooth", "rand", "stagger", "plateau", "shuffle"}
+ modes := []string{"copy", "reverse", "reverse1", "reverse2", "sort", "dither"}
+ var tmp1, tmp2 [1025]int
+ for ni := 0; ni < len(sizes); ni++ {
+ n := sizes[ni]
+ for m := 1; m < 2*n; m *= 2 {
+ for dist := 0; dist < _NDist; dist++ {
+ j := 0
+ k := 1
+ data := tmp1[0:n]
+ for i := 0; i < n; i++ {
+ switch dist {
+ case _Sawtooth:
+ data[i] = i % m
+ case _Rand:
+ data[i] = rand.Intn(m)
+ case _Stagger:
+ data[i] = (i*m + i) % n
+ case _Plateau:
+ data[i] = min(i, m)
+ case _Shuffle:
+ if rand.Intn(m) != 0 {
+ j += 2
+ data[i] = j
+ } else {
+ k += 2
+ data[i] = k
+ }
+ }
+ }
+
+ mdata := tmp2[0:n]
+ for mode := 0; mode < _NMode; mode++ {
+ switch mode {
+ case _Copy:
+ for i := 0; i < n; i++ {
+ mdata[i] = data[i]
+ }
+ case _Reverse:
+ for i := 0; i < n; i++ {
+ mdata[i] = data[n-i-1]
+ }
+ case _ReverseFirstHalf:
+ for i := 0; i < n/2; i++ {
+ mdata[i] = data[n/2-i-1]
+ }
+ for i := n / 2; i < n; i++ {
+ mdata[i] = data[i]
+ }
+ case _ReverseSecondHalf:
+ for i := 0; i < n/2; i++ {
+ mdata[i] = data[i]
+ }
+ for i := n / 2; i < n; i++ {
+ mdata[i] = data[n-(i-n/2)-1]
+ }
+ case _Sorted:
+ for i := 0; i < n; i++ {
+ mdata[i] = data[i]
+ }
+ // SortInts is known to be correct
+ // because mode Sort runs after mode _Copy.
+ SortInts(mdata)
+ case _Dither:
+ for i := 0; i < n; i++ {
+ mdata[i] = data[i] + i%5
+ }
+ }
+
+ desc := fmt.Sprintf("n=%d m=%d dist=%s mode=%s", n, m, dists[dist], modes[mode])
+ d := &testingData{desc, t, mdata[0:n], n * lg(n) * 12 / 10, 0}
+ Sort(d)
+
+ // If we were testing C qsort, we'd have to make a copy
+ // of the array and sort it ourselves and then compare
+ // x against it, to ensure that qsort was only permuting
+ // the data, not (for example) overwriting it with zeros.
+ //
+ // In go, we don't have to be so paranoid: since the only
+ // mutating method Sort can call is TestingData.swap,
+ // it suffices here just to check that the final array is sorted.
+ if !IntsAreSorted(mdata) {
+ t.Errorf("%s: ints not sorted", desc)
+ t.Errorf("\t%v", mdata)
+ t.FailNow()
+ }
+ }
+ }
+ }
+ }
+}