-
Notifications
You must be signed in to change notification settings - Fork 0
/
SparseArray.java
436 lines (373 loc) · 12.8 KB
/
SparseArray.java
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
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
// https://github.com/jzebedee/rhbackshiftdict/blob/master/src/robinhood/RobinHoodDictionary.cs
// https://github.com/goossaert/hashmap/blob/master/backshift_hashmap.cc
// http://codecapsule.com/2013/11/17/robin-hood-hashing-backward-shift-deletion/
import java.util.HashMap;
import java.util.Iterator;
import java.util.NoSuchElementException;
public final class SparseArray<T> {
private static final int MIN_CAPACITY = 16; // must be power of 2
private static final float MAX_LOAD_FACTOR = 0.85f;
private boolean frozen;
private int size;
private int capacity;
private long[] keyHashes; // key in upper 32 bits, and hash in lower
private T[] values;
public SparseArray() {
resize(MIN_CAPACITY);
}
public SparseArray(final int initialCapacity) {
resize(pow2Capacity(initialCapacity));
}
public SparseArray(final SparseArray<T> other) {
int neededCapacity = pow2Capacity(other.size);
if ((float)other.size / neededCapacity > MAX_LOAD_FACTOR) {
neededCapacity *= 2;
}
size = other.size;
keyHashes = other.keyHashes;
values = other.values;
resize(neededCapacity);
}
@Override
public boolean equals(final Object obj) {
if (!(obj instanceof SparseArray)) {
return false;
}
final SparseArray other = (SparseArray)obj;
if (other.size != size) {
return false;
}
int found = 0;
for (int i = 0; found < size; ++i) {
final long kh = keyHashes[i];
if ((int)kh != 0) {
final int j = other.find(kh);
if (j < 0 || !values[i].equals(other.values[j])) {
return false;
}
++found;
}
}
return true;
}
public int[] keys() {
final int[] keys = new int[size];
int found = 0;
for (int i = 0; found < size; ++i) {
final long kh = keyHashes[i];
if ((int)kh != 0) {
keys[found++] = (int)(kh >> 32);
}
}
return keys;
}
public Iterable<T> values() {
return new Iterable<T>() {
@Override
public Iterator<T> iterator() {
return new Iterator<T>() {
int index = 0;
int found = 0;
@Override
public boolean hasNext() {
return found < size;
}
@Override
public T next() {
for (; index < capacity; ++index) {
final T value = values[index];
if (value != null) {
++index;
++found;
return value;
}
}
throw new NoSuchElementException();
}
@Override
public void remove() {
throw new UnsupportedOperationException();
}
};
}
};
}
public int size() {
return size;
}
public int capacity() {
return capacity;
}
public boolean containsKey(final int key) {
return find(calcHashKey(key)) >= 0;
}
public T get(final int key) {
return get(key, null);
}
public T get(final int key, final T defaultValue) {
final int index = find(calcHashKey(key));
if (index >= 0) {
return values[index];
}
return defaultValue;
}
public void freeze() {
frozen = true;
}
public void clear() {
if (frozen) {
throw new UnsupportedOperationException();
}
for (int i = 0; i < capacity; ++i) {
keyHashes[i] = 0;
values[i] = null;
}
size = 0;
}
public void put(final int key, final T value) {
if (frozen) {
throw new UnsupportedOperationException();
}
if (value == null) {
throw new IllegalArgumentException("value is null");
}
if ((float)size / capacity > MAX_LOAD_FACTOR) {
resize(capacity * 2);
}
put(calcHashKey(key), value);
}
public boolean remove(final int key) {
if (frozen) {
throw new UnsupportedOperationException();
}
final int index = find(calcHashKey(key));
if (index < 0) {
return false;
}
for (int i = 0; i < capacity; ++i) {
final int curr = (index + i) & (capacity - 1);
final int next = (index + i + 1) & (capacity - 1);
final int h = (int)keyHashes[next];
if (h == 0 || distToHome(h, next) == 0) {
keyHashes[curr] = 0;
values[curr] = null;
--size;
return true;
}
// shift back next value closer to its home slot
keyHashes[curr] = keyHashes[next];
values[curr] = values[next];
}
throw new RuntimeException("control flow should not get here");
}
private void put(long keyHash, T value) {
final int startIndex = (int)keyHash & (capacity - 1);
int probe = 0; // probe distance from home slot
for (int i = 0; i < capacity; ++i, ++probe) {
final int index = (startIndex + i) & (capacity - 1);
final long kh = keyHashes[index];
final int h = (int)kh;
if (h == 0) {
keyHashes[index] = keyHash;
values[index] = value;
++size;
return;
}
if (kh == keyHash) {
values[index] = value;
return;
}
final int d = distToHome(h, index);
if (probe > d) {
// if we are farther from home than the encountered value, then we take its place
probe = d;
long tempHK = keyHashes[index];
T tempVal = values[index];
keyHashes[index] = keyHash;
values[index] = value;
keyHash = tempHK;
value = tempVal;
}
}
throw new RuntimeException("control flow should not get here");
}
private int find(final long keyHash) {
final int startIndex = (int)keyHash & (capacity - 1);
for (int i = 0; i < capacity; ++i) {
final int index = (startIndex + i) & (capacity - 1);
final long kh = keyHashes[index];
if (kh == keyHash) {
return index;
}
final int h = (int)kh;
if (h == 0) {
// if we encounter an empty slow we give up, since backward shifting on delete
// will leave no empty slots keeping a value away from its home slot
return -1;
}
int d = distToHome(h, index);
if (i > d) {
// if current probe distance is farther from home than that of encountered value,
// then we give up, since our value would have taken its place had it been present
return -1;
}
}
return -1;
}
@SuppressWarnings("unchecked")
private void resize(int newCapacity) {
if (newCapacity < size) {
throw new RuntimeException("new capacity is too small");
}
final int oldSize = size;
final long[] oldHashKeys = keyHashes;
final T[] oldValues = values;
size = 0;
capacity = newCapacity;
keyHashes = new long[newCapacity];
values = (T[]) new Object[newCapacity]; // unchecked cast
int found = 0;
for (int i = 0; found < oldSize; ++i) {
final long kh = oldHashKeys[i];
if ((int)kh != 0) {
put(kh, oldValues[i]);
++found;
}
}
}
private int distToHome(int hash, int indexStored) {
final int startIndex = hash & (capacity - 1);
if (startIndex <= indexStored) {
return indexStored - startIndex;
}
return indexStored + (capacity - startIndex);
}
private static long calcHashKey(int key) {
int hash = smear(key);
if (hash == 0) {
hash = 1; // don't allow hash of 0, so we can use that to distinguish lack of value
}
return ((long)key << 32) | (hash & 0xFFFFFFFFL);
}
/*
* This method was written by Doug Lea with assistance from members of JCP
* JSR-166 Expert Group and released to the public domain, as explained at
* http://creativecommons.org/licenses/publicdomain
*
* As of 2010/06/11, this method is identical to the (package private) hash
* method in OpenJDK 7's java.util.HashMap class.
*/
private static int smear(int hashCode) {
hashCode ^= (hashCode >>> 20) ^ (hashCode >>> 12);
return hashCode ^ (hashCode >>> 7) ^ (hashCode >>> 4);
}
private static int pow2Capacity(int x) {
if (x < MIN_CAPACITY) {
return MIN_CAPACITY;
}
// next higher power of two:
x = x - 1;
x |= x >> 1;
x |= x >> 2;
x |= x >> 4;
x |= x >> 8;
x |= x >> 16;
return x + 1;
}
public static void main(String[] args) {
System.out.println("hei");
testHashKeyPacking(0);
testHashKeyPacking(1);
testHashKeyPacking(-1);
testHashKeyPacking(255);
testHashKeyPacking(113254325);
testHashKeyPacking(Integer.MIN_VALUE);
testHashKeyPacking(Integer.MAX_VALUE);
assert pow2Capacity(0) == 16;
assert pow2Capacity(1) == 16;
assert pow2Capacity(-1) == 16;
assert pow2Capacity(10) == 16;
assert pow2Capacity(15) == 16;
assert pow2Capacity(16) == 16;
assert pow2Capacity(129) == 256;
assert pow2Capacity(255) == 256;
assert pow2Capacity(256) == 256;
SparseArray<Integer> arr = new SparseArray<>();
final int N = 100000;
for (int i = 0; i < N; ++i) {
arr.put(i, i);
arr.put(i, i);
}
int[] keys = arr.keys();
assert keys.length == N;
for (int i = 0; i < N; ++i) {
assert arr.get(i) == i;
assert arr.get(keys[i]) == keys[i];
}
int valueCount = 0;
SparseArray<Integer> arr2 = new SparseArray<>(N);
for (Integer val : arr.values()) {
int i = val;
assert arr2.get(i) == null;
arr2.put(i, i);
assert arr2.get(i) == i;
assert arr.get(i) == i;
++valueCount;
}
SparseArray<Integer> arr3 = new SparseArray<>(arr);
assert arr.equals(arr3);
assert arr.equals(arr2);
assert valueCount == N;
assert arr.size() == N;
assert arr.containsKey(100);
assert arr.remove(100);
assert !arr.remove(100);
assert !arr.containsKey(100);
assert arr.size() == N-1;
assert !arr.equals(arr2);
for (int i = 0; i < N; ++i) {
if (i != 100) {
assert arr.get(i) == i;
}
}
for (int i = 0; i < N; ++i) {
if (i != 100) {
assert arr.remove(i);
}
}
assert arr.size() == 0;
for (int i = 0; i < N; ++i) {
assert arr.get(i) == null;
}
final int COUNT = 10000000;
long start2 = System.currentTimeMillis();
SparseArray<Integer> sparseArray = new SparseArray<>();
for (int i = 0; i < COUNT; ++i) {
sparseArray.put(i, i);
}
for (int i = 0; i < COUNT; ++i) {
assert sparseArray.containsKey(i);
assert sparseArray.containsKey(i ^ 13);
}
System.out.println("SparseArray: " + ((System.currentTimeMillis() - start2) / 1000.0));
long start1 = System.currentTimeMillis();
HashMap<Integer, Integer> hashMap = new HashMap<>();
for (int i = 0; i < COUNT; ++i) {
hashMap.put(i, i);
}
for (int i = 0; i < COUNT; ++i) {
assert hashMap.containsKey(i);
assert hashMap.containsKey(i ^ 13);
}
System.out.println("HashMap: " + ((System.currentTimeMillis() - start1) / 1000.0));
}
private static void testHashKeyPacking(int key) {
long kh = calcHashKey(key);
int hash = smear(key);
if (hash == 0) {
hash = 1;
}
assert key == (int)(kh >> 32) : "error extracting key";
assert hash == (int)kh : "error extracting hash";
}
}