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
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
|
// Copyright 2013 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 gc
import (
"math/bits"
)
const (
wordBits = 32
wordMask = wordBits - 1
wordShift = 5
)
// A bvec is a bit vector.
type bvec struct {
n int32 // number of bits in vector
b []uint32 // words holding bits
}
func bvalloc(n int32) bvec {
nword := (n + wordBits - 1) / wordBits
return bvec{n, make([]uint32, nword)}
}
type bulkBvec struct {
words []uint32
nbit int32
nword int32
}
func bvbulkalloc(nbit int32, count int32) bulkBvec {
nword := (nbit + wordBits - 1) / wordBits
size := int64(nword) * int64(count)
if int64(int32(size*4)) != size*4 {
Fatalf("bvbulkalloc too big: nbit=%d count=%d nword=%d size=%d", nbit, count, nword, size)
}
return bulkBvec{
words: make([]uint32, size),
nbit: nbit,
nword: nword,
}
}
func (b *bulkBvec) next() bvec {
out := bvec{b.nbit, b.words[:b.nword]}
b.words = b.words[b.nword:]
return out
}
func (bv1 bvec) Eq(bv2 bvec) bool {
if bv1.n != bv2.n {
Fatalf("bvequal: lengths %d and %d are not equal", bv1.n, bv2.n)
}
for i, x := range bv1.b {
if x != bv2.b[i] {
return false
}
}
return true
}
func (dst bvec) Copy(src bvec) {
copy(dst.b, src.b)
}
func (bv bvec) Get(i int32) bool {
if i < 0 || i >= bv.n {
Fatalf("bvget: index %d is out of bounds with length %d\n", i, bv.n)
}
mask := uint32(1 << uint(i%wordBits))
return bv.b[i>>wordShift]&mask != 0
}
func (bv bvec) Set(i int32) {
if i < 0 || i >= bv.n {
Fatalf("bvset: index %d is out of bounds with length %d\n", i, bv.n)
}
mask := uint32(1 << uint(i%wordBits))
bv.b[i/wordBits] |= mask
}
func (bv bvec) Unset(i int32) {
if i < 0 || i >= bv.n {
Fatalf("bvunset: index %d is out of bounds with length %d\n", i, bv.n)
}
mask := uint32(1 << uint(i%wordBits))
bv.b[i/wordBits] &^= mask
}
// bvnext returns the smallest index >= i for which bvget(bv, i) == 1.
// If there is no such index, bvnext returns -1.
func (bv bvec) Next(i int32) int32 {
if i >= bv.n {
return -1
}
// Jump i ahead to next word with bits.
if bv.b[i>>wordShift]>>uint(i&wordMask) == 0 {
i &^= wordMask
i += wordBits
for i < bv.n && bv.b[i>>wordShift] == 0 {
i += wordBits
}
}
if i >= bv.n {
return -1
}
// Find 1 bit.
w := bv.b[i>>wordShift] >> uint(i&wordMask)
i += int32(bits.TrailingZeros32(w))
return i
}
func (bv bvec) IsEmpty() bool {
for _, x := range bv.b {
if x != 0 {
return false
}
}
return true
}
func (bv bvec) Not() {
for i, x := range bv.b {
bv.b[i] = ^x
}
}
// union
func (dst bvec) Or(src1, src2 bvec) {
if len(src1.b) == 0 {
return
}
_, _ = dst.b[len(src1.b)-1], src2.b[len(src1.b)-1] // hoist bounds checks out of the loop
for i, x := range src1.b {
dst.b[i] = x | src2.b[i]
}
}
// intersection
func (dst bvec) And(src1, src2 bvec) {
if len(src1.b) == 0 {
return
}
_, _ = dst.b[len(src1.b)-1], src2.b[len(src1.b)-1] // hoist bounds checks out of the loop
for i, x := range src1.b {
dst.b[i] = x & src2.b[i]
}
}
// difference
func (dst bvec) AndNot(src1, src2 bvec) {
if len(src1.b) == 0 {
return
}
_, _ = dst.b[len(src1.b)-1], src2.b[len(src1.b)-1] // hoist bounds checks out of the loop
for i, x := range src1.b {
dst.b[i] = x &^ src2.b[i]
}
}
func (bv bvec) String() string {
s := make([]byte, 2+bv.n)
copy(s, "#*")
for i := int32(0); i < bv.n; i++ {
ch := byte('0')
if bv.Get(i) {
ch = '1'
}
s[2+i] = ch
}
return string(s)
}
func (bv bvec) Clear() {
for i := range bv.b {
bv.b[i] = 0
}
}
// FNV-1 hash function constants.
const (
H0 = 2166136261
Hp = 16777619
)
func hashbitmap(h uint32, bv bvec) uint32 {
n := int((bv.n + 31) / 32)
for i := 0; i < n; i++ {
w := bv.b[i]
h = (h * Hp) ^ (w & 0xff)
h = (h * Hp) ^ ((w >> 8) & 0xff)
h = (h * Hp) ^ ((w >> 16) & 0xff)
h = (h * Hp) ^ ((w >> 24) & 0xff)
}
return h
}
// bvecSet is a set of bvecs, in initial insertion order.
type bvecSet struct {
index []int // hash -> uniq index. -1 indicates empty slot.
uniq []bvec // unique bvecs, in insertion order
}
func (m *bvecSet) grow() {
// Allocate new index.
n := len(m.index) * 2
if n == 0 {
n = 32
}
newIndex := make([]int, n)
for i := range newIndex {
newIndex[i] = -1
}
// Rehash into newIndex.
for i, bv := range m.uniq {
h := hashbitmap(H0, bv) % uint32(len(newIndex))
for {
j := newIndex[h]
if j < 0 {
newIndex[h] = i
break
}
h++
if h == uint32(len(newIndex)) {
h = 0
}
}
}
m.index = newIndex
}
// add adds bv to the set and returns its index in m.extractUniqe.
// The caller must not modify bv after this.
func (m *bvecSet) add(bv bvec) int {
if len(m.uniq)*4 >= len(m.index) {
m.grow()
}
index := m.index
h := hashbitmap(H0, bv) % uint32(len(index))
for {
j := index[h]
if j < 0 {
// New bvec.
index[h] = len(m.uniq)
m.uniq = append(m.uniq, bv)
return len(m.uniq) - 1
}
jlive := m.uniq[j]
if bv.Eq(jlive) {
// Existing bvec.
return j
}
h++
if h == uint32(len(index)) {
h = 0
}
}
}
// extractUniqe returns this slice of unique bit vectors in m, as
// indexed by the result of bvecSet.add.
func (m *bvecSet) extractUniqe() []bvec {
return m.uniq
}
|
