Source Code Cross Referenced for BitUtil.java in  » Search-Engine » apache-solr-1.2.0 » org » apache » solr » util » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » Search Engine » apache solr 1.2.0 » org.apache.solr.util 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        /**
002:         * Licensed to the Apache Software Foundation (ASF) under one or more
003:         * contributor license agreements.  See the NOTICE file distributed with
004:         * this work for additional information regarding copyright ownership.
005:         * The ASF licenses this file to You under the Apache License, Version 2.0
006:         * (the "License"); you may not use this file except in compliance with
007:         * the License.  You may obtain a copy of the License at
008:         *
009:         *     http://www.apache.org/licenses/LICENSE-2.0
010:         *
011:         * Unless required by applicable law or agreed to in writing, software
012:         * distributed under the License is distributed on an "AS IS" BASIS,
013:         * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014:         * See the License for the specific language governing permissions and
015:         * limitations under the License.
016:         */package org.apache.solr.util;
017:
018:        /**  A variety of high efficiencly bit twiddling routines.
019:         *
020:         * @author yonik
021:         * @version $Id$
022:         */
023:        public class BitUtil {
024:
025:            /** Returns the number of bits set in the long */
026:            public static int pop(long x) {
027:                /* Hacker's Delight 32 bit pop function:
028:                 * http://www.hackersdelight.org/HDcode/newCode/pop_arrayHS.cc
029:                 *
030:                int pop(unsigned x) {
031:                   x = x - ((x >> 1) & 0x55555555);
032:                   x = (x & 0x33333333) + ((x >> 2) & 0x33333333);
033:                   x = (x + (x >> 4)) & 0x0F0F0F0F;
034:                   x = x + (x >> 8);
035:                   x = x + (x >> 16);
036:                   return x & 0x0000003F;
037:                  }
038:                 ***/
039:
040:                // 64 bit java version of the C function from above
041:                x = x - ((x >>> 1) & 0x5555555555555555L);
042:                x = (x & 0x3333333333333333L)
043:                        + ((x >>> 2) & 0x3333333333333333L);
044:                x = (x + (x >>> 4)) & 0x0F0F0F0F0F0F0F0FL;
045:                x = x + (x >>> 8);
046:                x = x + (x >>> 16);
047:                x = x + (x >>> 32);
048:                return ((int) x) & 0x7F;
049:            }
050:
051:            /*** Returns the number of set bits in an array of longs. */
052:            public static long pop_array(long A[], int wordOffset, int numWords) {
053:                /*
054:                 * Robert Harley and David Seal's bit counting algorithm, as documented
055:                 * in the revisions of Hacker's Delight
056:                 * http://www.hackersdelight.org/revisions.pdf
057:                 * http://www.hackersdelight.org/HDcode/newCode/pop_arrayHS.cc
058:                 *
059:                 * This function was adapted to Java, and extended to use 64 bit words.
060:                 * if only we had access to wider registers like SSE from java...
061:                 *
062:                 * This function can be transformed to compute the popcount of other functions
063:                 * on bitsets via something like this:
064:                 * sed 's/A\[\([^]]*\)\]/\(A[\1] \& B[\1]\)/g'
065:                 *
066:                 */
067:                int n = wordOffset + numWords;
068:                long tot = 0, tot8 = 0;
069:                long ones = 0, twos = 0, fours = 0;
070:
071:                int i;
072:                for (i = wordOffset; i <= n - 8; i += 8) {
073:                    /***  C macro from Hacker's Delight
074:                     #define CSA(h,l, a,b,c) \
075:                     {unsigned u = a ^ b; unsigned v = c; \
076:                     h = (a & b) | (u & v); l = u ^ v;}
077:                     ***/
078:
079:                    long twosA, twosB, foursA, foursB, eights;
080:
081:                    // CSA(twosA, ones, ones, A[i], A[i+1])
082:                    {
083:                        long b = A[i], c = A[i + 1];
084:                        long u = ones ^ b;
085:                        twosA = (ones & b) | (u & c);
086:                        ones = u ^ c;
087:                    }
088:                    // CSA(twosB, ones, ones, A[i+2], A[i+3])
089:                    {
090:                        long b = A[i + 2], c = A[i + 3];
091:                        long u = ones ^ b;
092:                        twosB = (ones & b) | (u & c);
093:                        ones = u ^ c;
094:                    }
095:                    //CSA(foursA, twos, twos, twosA, twosB)
096:                    {
097:                        long u = twos ^ twosA;
098:                        foursA = (twos & twosA) | (u & twosB);
099:                        twos = u ^ twosB;
100:                    }
101:                    //CSA(twosA, ones, ones, A[i+4], A[i+5])
102:                    {
103:                        long b = A[i + 4], c = A[i + 5];
104:                        long u = ones ^ b;
105:                        twosA = (ones & b) | (u & c);
106:                        ones = u ^ c;
107:                    }
108:                    // CSA(twosB, ones, ones, A[i+6], A[i+7])
109:                    {
110:                        long b = A[i + 6], c = A[i + 7];
111:                        long u = ones ^ b;
112:                        twosB = (ones & b) | (u & c);
113:                        ones = u ^ c;
114:                    }
115:                    //CSA(foursB, twos, twos, twosA, twosB)
116:                    {
117:                        long u = twos ^ twosA;
118:                        foursB = (twos & twosA) | (u & twosB);
119:                        twos = u ^ twosB;
120:                    }
121:
122:                    //CSA(eights, fours, fours, foursA, foursB)
123:                    {
124:                        long u = fours ^ foursA;
125:                        eights = (fours & foursA) | (u & foursB);
126:                        fours = u ^ foursB;
127:                    }
128:                    tot8 += pop(eights);
129:                }
130:
131:                // handle trailing words in a binary-search manner...
132:                // derived from the loop above by setting specific elements to 0.
133:                // the original method in Hackers Delight used a simple for loop:
134:                //   for (i = i; i < n; i++)      // Add in the last elements
135:                //  tot = tot + pop(A[i]);
136:
137:                if (i <= n - 4) {
138:                    long twosA, twosB, foursA, eights;
139:                    {
140:                        long b = A[i], c = A[i + 1];
141:                        long u = ones ^ b;
142:                        twosA = (ones & b) | (u & c);
143:                        ones = u ^ c;
144:                    }
145:                    {
146:                        long b = A[i + 2], c = A[i + 3];
147:                        long u = ones ^ b;
148:                        twosB = (ones & b) | (u & c);
149:                        ones = u ^ c;
150:                    }
151:                    {
152:                        long u = twos ^ twosA;
153:                        foursA = (twos & twosA) | (u & twosB);
154:                        twos = u ^ twosB;
155:                    }
156:                    eights = fours & foursA;
157:                    fours = fours ^ foursA;
158:
159:                    tot8 += pop(eights);
160:                    i += 4;
161:                }
162:
163:                if (i <= n - 2) {
164:                    long b = A[i], c = A[i + 1];
165:                    long u = ones ^ b;
166:                    long twosA = (ones & b) | (u & c);
167:                    ones = u ^ c;
168:
169:                    long foursA = twos & twosA;
170:                    twos = twos ^ twosA;
171:
172:                    long eights = fours & foursA;
173:                    fours = fours ^ foursA;
174:
175:                    tot8 += pop(eights);
176:                    i += 2;
177:                }
178:
179:                if (i < n) {
180:                    tot += pop(A[i]);
181:                }
182:
183:                tot += (pop(fours) << 2) + (pop(twos) << 1) + pop(ones)
184:                        + (tot8 << 3);
185:
186:                return tot;
187:            }
188:
189:            /** Returns the popcount or cardinality of the two sets after an intersection.
190:             * Neither array is modified.
191:             */
192:            public static long pop_intersect(long A[], long B[],
193:                    int wordOffset, int numWords) {
194:                // generated from pop_array via sed 's/A\[\([^]]*\)\]/\(A[\1] \& B[\1]\)/g'
195:                int n = wordOffset + numWords;
196:                long tot = 0, tot8 = 0;
197:                long ones = 0, twos = 0, fours = 0;
198:
199:                int i;
200:                for (i = wordOffset; i <= n - 8; i += 8) {
201:                    long twosA, twosB, foursA, foursB, eights;
202:
203:                    // CSA(twosA, ones, ones, (A[i] & B[i]), (A[i+1] & B[i+1]))
204:                    {
205:                        long b = (A[i] & B[i]), c = (A[i + 1] & B[i + 1]);
206:                        long u = ones ^ b;
207:                        twosA = (ones & b) | (u & c);
208:                        ones = u ^ c;
209:                    }
210:                    // CSA(twosB, ones, ones, (A[i+2] & B[i+2]), (A[i+3] & B[i+3]))
211:                    {
212:                        long b = (A[i + 2] & B[i + 2]), c = (A[i + 3] & B[i + 3]);
213:                        long u = ones ^ b;
214:                        twosB = (ones & b) | (u & c);
215:                        ones = u ^ c;
216:                    }
217:                    //CSA(foursA, twos, twos, twosA, twosB)
218:                    {
219:                        long u = twos ^ twosA;
220:                        foursA = (twos & twosA) | (u & twosB);
221:                        twos = u ^ twosB;
222:                    }
223:                    //CSA(twosA, ones, ones, (A[i+4] & B[i+4]), (A[i+5] & B[i+5]))
224:                    {
225:                        long b = (A[i + 4] & B[i + 4]), c = (A[i + 5] & B[i + 5]);
226:                        long u = ones ^ b;
227:                        twosA = (ones & b) | (u & c);
228:                        ones = u ^ c;
229:                    }
230:                    // CSA(twosB, ones, ones, (A[i+6] & B[i+6]), (A[i+7] & B[i+7]))
231:                    {
232:                        long b = (A[i + 6] & B[i + 6]), c = (A[i + 7] & B[i + 7]);
233:                        long u = ones ^ b;
234:                        twosB = (ones & b) | (u & c);
235:                        ones = u ^ c;
236:                    }
237:                    //CSA(foursB, twos, twos, twosA, twosB)
238:                    {
239:                        long u = twos ^ twosA;
240:                        foursB = (twos & twosA) | (u & twosB);
241:                        twos = u ^ twosB;
242:                    }
243:
244:                    //CSA(eights, fours, fours, foursA, foursB)
245:                    {
246:                        long u = fours ^ foursA;
247:                        eights = (fours & foursA) | (u & foursB);
248:                        fours = u ^ foursB;
249:                    }
250:                    tot8 += pop(eights);
251:                }
252:
253:                if (i <= n - 4) {
254:                    long twosA, twosB, foursA, eights;
255:                    {
256:                        long b = (A[i] & B[i]), c = (A[i + 1] & B[i + 1]);
257:                        long u = ones ^ b;
258:                        twosA = (ones & b) | (u & c);
259:                        ones = u ^ c;
260:                    }
261:                    {
262:                        long b = (A[i + 2] & B[i + 2]), c = (A[i + 3] & B[i + 3]);
263:                        long u = ones ^ b;
264:                        twosB = (ones & b) | (u & c);
265:                        ones = u ^ c;
266:                    }
267:                    {
268:                        long u = twos ^ twosA;
269:                        foursA = (twos & twosA) | (u & twosB);
270:                        twos = u ^ twosB;
271:                    }
272:                    eights = fours & foursA;
273:                    fours = fours ^ foursA;
274:
275:                    tot8 += pop(eights);
276:                    i += 4;
277:                }
278:
279:                if (i <= n - 2) {
280:                    long b = (A[i] & B[i]), c = (A[i + 1] & B[i + 1]);
281:                    long u = ones ^ b;
282:                    long twosA = (ones & b) | (u & c);
283:                    ones = u ^ c;
284:
285:                    long foursA = twos & twosA;
286:                    twos = twos ^ twosA;
287:
288:                    long eights = fours & foursA;
289:                    fours = fours ^ foursA;
290:
291:                    tot8 += pop(eights);
292:                    i += 2;
293:                }
294:
295:                if (i < n) {
296:                    tot += pop((A[i] & B[i]));
297:                }
298:
299:                tot += (pop(fours) << 2) + (pop(twos) << 1) + pop(ones)
300:                        + (tot8 << 3);
301:
302:                return tot;
303:            }
304:
305:            /** Returns the popcount or cardinality of the union of two sets.
306:             * Neither array is modified.
307:             */
308:            public static long pop_union(long A[], long B[], int wordOffset,
309:                    int numWords) {
310:                // generated from pop_array via sed 's/A\[\([^]]*\)\]/\(A[\1] \| B[\1]\)/g'
311:                int n = wordOffset + numWords;
312:                long tot = 0, tot8 = 0;
313:                long ones = 0, twos = 0, fours = 0;
314:
315:                int i;
316:                for (i = wordOffset; i <= n - 8; i += 8) {
317:                    /***  C macro from Hacker's Delight
318:                     #define CSA(h,l, a,b,c) \
319:                     {unsigned u = a ^ b; unsigned v = c; \
320:                     h = (a & b) | (u & v); l = u ^ v;}
321:                     ***/
322:
323:                    long twosA, twosB, foursA, foursB, eights;
324:
325:                    // CSA(twosA, ones, ones, (A[i] | B[i]), (A[i+1] | B[i+1]))
326:                    {
327:                        long b = (A[i] | B[i]), c = (A[i + 1] | B[i + 1]);
328:                        long u = ones ^ b;
329:                        twosA = (ones & b) | (u & c);
330:                        ones = u ^ c;
331:                    }
332:                    // CSA(twosB, ones, ones, (A[i+2] | B[i+2]), (A[i+3] | B[i+3]))
333:                    {
334:                        long b = (A[i + 2] | B[i + 2]), c = (A[i + 3] | B[i + 3]);
335:                        long u = ones ^ b;
336:                        twosB = (ones & b) | (u & c);
337:                        ones = u ^ c;
338:                    }
339:                    //CSA(foursA, twos, twos, twosA, twosB)
340:                    {
341:                        long u = twos ^ twosA;
342:                        foursA = (twos & twosA) | (u & twosB);
343:                        twos = u ^ twosB;
344:                    }
345:                    //CSA(twosA, ones, ones, (A[i+4] | B[i+4]), (A[i+5] | B[i+5]))
346:                    {
347:                        long b = (A[i + 4] | B[i + 4]), c = (A[i + 5] | B[i + 5]);
348:                        long u = ones ^ b;
349:                        twosA = (ones & b) | (u & c);
350:                        ones = u ^ c;
351:                    }
352:                    // CSA(twosB, ones, ones, (A[i+6] | B[i+6]), (A[i+7] | B[i+7]))
353:                    {
354:                        long b = (A[i + 6] | B[i + 6]), c = (A[i + 7] | B[i + 7]);
355:                        long u = ones ^ b;
356:                        twosB = (ones & b) | (u & c);
357:                        ones = u ^ c;
358:                    }
359:                    //CSA(foursB, twos, twos, twosA, twosB)
360:                    {
361:                        long u = twos ^ twosA;
362:                        foursB = (twos & twosA) | (u & twosB);
363:                        twos = u ^ twosB;
364:                    }
365:
366:                    //CSA(eights, fours, fours, foursA, foursB)
367:                    {
368:                        long u = fours ^ foursA;
369:                        eights = (fours & foursA) | (u & foursB);
370:                        fours = u ^ foursB;
371:                    }
372:                    tot8 += pop(eights);
373:                }
374:
375:                if (i <= n - 4) {
376:                    long twosA, twosB, foursA, eights;
377:                    {
378:                        long b = (A[i] | B[i]), c = (A[i + 1] | B[i + 1]);
379:                        long u = ones ^ b;
380:                        twosA = (ones & b) | (u & c);
381:                        ones = u ^ c;
382:                    }
383:                    {
384:                        long b = (A[i + 2] | B[i + 2]), c = (A[i + 3] | B[i + 3]);
385:                        long u = ones ^ b;
386:                        twosB = (ones & b) | (u & c);
387:                        ones = u ^ c;
388:                    }
389:                    {
390:                        long u = twos ^ twosA;
391:                        foursA = (twos & twosA) | (u & twosB);
392:                        twos = u ^ twosB;
393:                    }
394:                    eights = fours & foursA;
395:                    fours = fours ^ foursA;
396:
397:                    tot8 += pop(eights);
398:                    i += 4;
399:                }
400:
401:                if (i <= n - 2) {
402:                    long b = (A[i] | B[i]), c = (A[i + 1] | B[i + 1]);
403:                    long u = ones ^ b;
404:                    long twosA = (ones & b) | (u & c);
405:                    ones = u ^ c;
406:
407:                    long foursA = twos & twosA;
408:                    twos = twos ^ twosA;
409:
410:                    long eights = fours & foursA;
411:                    fours = fours ^ foursA;
412:
413:                    tot8 += pop(eights);
414:                    i += 2;
415:                }
416:
417:                if (i < n) {
418:                    tot += pop((A[i] | B[i]));
419:                }
420:
421:                tot += (pop(fours) << 2) + (pop(twos) << 1) + pop(ones)
422:                        + (tot8 << 3);
423:
424:                return tot;
425:            }
426:
427:            /** Returns the popcount or cardinality of A & ~B
428:             * Neither array is modified.
429:             */
430:            public static long pop_andnot(long A[], long B[], int wordOffset,
431:                    int numWords) {
432:                // generated from pop_array via sed 's/A\[\([^]]*\)\]/\(A[\1] \& ~B[\1]\)/g'
433:                int n = wordOffset + numWords;
434:                long tot = 0, tot8 = 0;
435:                long ones = 0, twos = 0, fours = 0;
436:
437:                int i;
438:                for (i = wordOffset; i <= n - 8; i += 8) {
439:                    /***  C macro from Hacker's Delight
440:                     #define CSA(h,l, a,b,c) \
441:                     {unsigned u = a ^ b; unsigned v = c; \
442:                     h = (a & b) | (u & v); l = u ^ v;}
443:                     ***/
444:
445:                    long twosA, twosB, foursA, foursB, eights;
446:
447:                    // CSA(twosA, ones, ones, (A[i] & ~B[i]), (A[i+1] & ~B[i+1]))
448:                    {
449:                        long b = (A[i] & ~B[i]), c = (A[i + 1] & ~B[i + 1]);
450:                        long u = ones ^ b;
451:                        twosA = (ones & b) | (u & c);
452:                        ones = u ^ c;
453:                    }
454:                    // CSA(twosB, ones, ones, (A[i+2] & ~B[i+2]), (A[i+3] & ~B[i+3]))
455:                    {
456:                        long b = (A[i + 2] & ~B[i + 2]), c = (A[i + 3] & ~B[i + 3]);
457:                        long u = ones ^ b;
458:                        twosB = (ones & b) | (u & c);
459:                        ones = u ^ c;
460:                    }
461:                    //CSA(foursA, twos, twos, twosA, twosB)
462:                    {
463:                        long u = twos ^ twosA;
464:                        foursA = (twos & twosA) | (u & twosB);
465:                        twos = u ^ twosB;
466:                    }
467:                    //CSA(twosA, ones, ones, (A[i+4] & ~B[i+4]), (A[i+5] & ~B[i+5]))
468:                    {
469:                        long b = (A[i + 4] & ~B[i + 4]), c = (A[i + 5] & ~B[i + 5]);
470:                        long u = ones ^ b;
471:                        twosA = (ones & b) | (u & c);
472:                        ones = u ^ c;
473:                    }
474:                    // CSA(twosB, ones, ones, (A[i+6] & ~B[i+6]), (A[i+7] & ~B[i+7]))
475:                    {
476:                        long b = (A[i + 6] & ~B[i + 6]), c = (A[i + 7] & ~B[i + 7]);
477:                        long u = ones ^ b;
478:                        twosB = (ones & b) | (u & c);
479:                        ones = u ^ c;
480:                    }
481:                    //CSA(foursB, twos, twos, twosA, twosB)
482:                    {
483:                        long u = twos ^ twosA;
484:                        foursB = (twos & twosA) | (u & twosB);
485:                        twos = u ^ twosB;
486:                    }
487:
488:                    //CSA(eights, fours, fours, foursA, foursB)
489:                    {
490:                        long u = fours ^ foursA;
491:                        eights = (fours & foursA) | (u & foursB);
492:                        fours = u ^ foursB;
493:                    }
494:                    tot8 += pop(eights);
495:                }
496:
497:                if (i <= n - 4) {
498:                    long twosA, twosB, foursA, eights;
499:                    {
500:                        long b = (A[i] & ~B[i]), c = (A[i + 1] & ~B[i + 1]);
501:                        long u = ones ^ b;
502:                        twosA = (ones & b) | (u & c);
503:                        ones = u ^ c;
504:                    }
505:                    {
506:                        long b = (A[i + 2] & ~B[i + 2]), c = (A[i + 3] & ~B[i + 3]);
507:                        long u = ones ^ b;
508:                        twosB = (ones & b) | (u & c);
509:                        ones = u ^ c;
510:                    }
511:                    {
512:                        long u = twos ^ twosA;
513:                        foursA = (twos & twosA) | (u & twosB);
514:                        twos = u ^ twosB;
515:                    }
516:                    eights = fours & foursA;
517:                    fours = fours ^ foursA;
518:
519:                    tot8 += pop(eights);
520:                    i += 4;
521:                }
522:
523:                if (i <= n - 2) {
524:                    long b = (A[i] & ~B[i]), c = (A[i + 1] & ~B[i + 1]);
525:                    long u = ones ^ b;
526:                    long twosA = (ones & b) | (u & c);
527:                    ones = u ^ c;
528:
529:                    long foursA = twos & twosA;
530:                    twos = twos ^ twosA;
531:
532:                    long eights = fours & foursA;
533:                    fours = fours ^ foursA;
534:
535:                    tot8 += pop(eights);
536:                    i += 2;
537:                }
538:
539:                if (i < n) {
540:                    tot += pop((A[i] & ~B[i]));
541:                }
542:
543:                tot += (pop(fours) << 2) + (pop(twos) << 1) + pop(ones)
544:                        + (tot8 << 3);
545:
546:                return tot;
547:            }
548:
549:            public static long pop_xor(long A[], long B[], int wordOffset,
550:                    int numWords) {
551:                int n = wordOffset + numWords;
552:                long tot = 0, tot8 = 0;
553:                long ones = 0, twos = 0, fours = 0;
554:
555:                int i;
556:                for (i = wordOffset; i <= n - 8; i += 8) {
557:                    /***  C macro from Hacker's Delight
558:                     #define CSA(h,l, a,b,c) \
559:                     {unsigned u = a ^ b; unsigned v = c; \
560:                     h = (a & b) | (u & v); l = u ^ v;}
561:                     ***/
562:
563:                    long twosA, twosB, foursA, foursB, eights;
564:
565:                    // CSA(twosA, ones, ones, (A[i] ^ B[i]), (A[i+1] ^ B[i+1]))
566:                    {
567:                        long b = (A[i] ^ B[i]), c = (A[i + 1] ^ B[i + 1]);
568:                        long u = ones ^ b;
569:                        twosA = (ones & b) | (u & c);
570:                        ones = u ^ c;
571:                    }
572:                    // CSA(twosB, ones, ones, (A[i+2] ^ B[i+2]), (A[i+3] ^ B[i+3]))
573:                    {
574:                        long b = (A[i + 2] ^ B[i + 2]), c = (A[i + 3] ^ B[i + 3]);
575:                        long u = ones ^ b;
576:                        twosB = (ones & b) | (u & c);
577:                        ones = u ^ c;
578:                    }
579:                    //CSA(foursA, twos, twos, twosA, twosB)
580:                    {
581:                        long u = twos ^ twosA;
582:                        foursA = (twos & twosA) | (u & twosB);
583:                        twos = u ^ twosB;
584:                    }
585:                    //CSA(twosA, ones, ones, (A[i+4] ^ B[i+4]), (A[i+5] ^ B[i+5]))
586:                    {
587:                        long b = (A[i + 4] ^ B[i + 4]), c = (A[i + 5] ^ B[i + 5]);
588:                        long u = ones ^ b;
589:                        twosA = (ones & b) | (u & c);
590:                        ones = u ^ c;
591:                    }
592:                    // CSA(twosB, ones, ones, (A[i+6] ^ B[i+6]), (A[i+7] ^ B[i+7]))
593:                    {
594:                        long b = (A[i + 6] ^ B[i + 6]), c = (A[i + 7] ^ B[i + 7]);
595:                        long u = ones ^ b;
596:                        twosB = (ones & b) | (u & c);
597:                        ones = u ^ c;
598:                    }
599:                    //CSA(foursB, twos, twos, twosA, twosB)
600:                    {
601:                        long u = twos ^ twosA;
602:                        foursB = (twos & twosA) | (u & twosB);
603:                        twos = u ^ twosB;
604:                    }
605:
606:                    //CSA(eights, fours, fours, foursA, foursB)
607:                    {
608:                        long u = fours ^ foursA;
609:                        eights = (fours & foursA) | (u & foursB);
610:                        fours = u ^ foursB;
611:                    }
612:                    tot8 += pop(eights);
613:                }
614:
615:                if (i <= n - 4) {
616:                    long twosA, twosB, foursA, eights;
617:                    {
618:                        long b = (A[i] ^ B[i]), c = (A[i + 1] ^ B[i + 1]);
619:                        long u = ones ^ b;
620:                        twosA = (ones & b) | (u & c);
621:                        ones = u ^ c;
622:                    }
623:                    {
624:                        long b = (A[i + 2] ^ B[i + 2]), c = (A[i + 3] ^ B[i + 3]);
625:                        long u = ones ^ b;
626:                        twosB = (ones & b) | (u & c);
627:                        ones = u ^ c;
628:                    }
629:                    {
630:                        long u = twos ^ twosA;
631:                        foursA = (twos & twosA) | (u & twosB);
632:                        twos = u ^ twosB;
633:                    }
634:                    eights = fours & foursA;
635:                    fours = fours ^ foursA;
636:
637:                    tot8 += pop(eights);
638:                    i += 4;
639:                }
640:
641:                if (i <= n - 2) {
642:                    long b = (A[i] ^ B[i]), c = (A[i + 1] ^ B[i + 1]);
643:                    long u = ones ^ b;
644:                    long twosA = (ones & b) | (u & c);
645:                    ones = u ^ c;
646:
647:                    long foursA = twos & twosA;
648:                    twos = twos ^ twosA;
649:
650:                    long eights = fours & foursA;
651:                    fours = fours ^ foursA;
652:
653:                    tot8 += pop(eights);
654:                    i += 2;
655:                }
656:
657:                if (i < n) {
658:                    tot += pop((A[i] ^ B[i]));
659:                }
660:
661:                tot += (pop(fours) << 2) + (pop(twos) << 1) + pop(ones)
662:                        + (tot8 << 3);
663:
664:                return tot;
665:            }
666:
667:            /* python code to generate ntzTable
668:            def ntz(val):
669:              if val==0: return 8
670:              i=0
671:              while (val&0x01)==0:
672:                i = i+1
673:                val >>= 1
674:              return i
675:            print ','.join([ str(ntz(i)) for i in range(256) ])
676:             ***/
677:            /** table of number of trailing zeros in a byte */
678:            public static final byte[] ntzTable = { 8, 0, 1, 0, 2, 0, 1, 0, 3,
679:                    0, 1, 0, 2, 0, 1, 0, 4, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2,
680:                    0, 1, 0, 5, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 4,
681:                    0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 6, 0, 1, 0, 2,
682:                    0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 4, 0, 1, 0, 2, 0, 1, 0, 3,
683:                    0, 1, 0, 2, 0, 1, 0, 5, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2,
684:                    0, 1, 0, 4, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 7,
685:                    0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 4, 0, 1, 0, 2,
686:                    0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 5, 0, 1, 0, 2, 0, 1, 0, 3,
687:                    0, 1, 0, 2, 0, 1, 0, 4, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2,
688:                    0, 1, 0, 6, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 4,
689:                    0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 5, 0, 1, 0, 2,
690:                    0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 4, 0, 1, 0, 2, 0, 1, 0, 3,
691:                    0, 1, 0, 2, 0, 1, 0 };
692:
693:            /** Returns number of trailing zeros in the 64 bit long value. */
694:            public static int ntz(long val) {
695:                // A full binary search to determine the low byte was slower than
696:                // a linear search for nextSetBit().  This is most likely because
697:                // the implementation of nextSetBit() shifts bits to the right, increasing
698:                // the probability that the first non-zero byte is in the rhs.
699:                //
700:                // This implementation does a single binary search at the top level only
701:                // so that all other bit shifting can be done on ints instead of longs to
702:                // remain friendly to 32 bit architectures.  In addition, the case of a
703:                // non-zero first byte is checked for first because it is the most common
704:                // in dense bit arrays.
705:
706:                int lower = (int) val;
707:                int lowByte = lower & 0xff;
708:                if (lowByte != 0)
709:                    return ntzTable[lowByte];
710:
711:                if (lower != 0) {
712:                    lowByte = (lower >>> 8) & 0xff;
713:                    if (lowByte != 0)
714:                        return ntzTable[lowByte] + 8;
715:                    lowByte = (lower >>> 16) & 0xff;
716:                    if (lowByte != 0)
717:                        return ntzTable[lowByte] + 16;
718:                    // no need to mask off low byte for the last byte in the 32 bit word
719:                    // no need to check for zero on the last byte either.
720:                    return ntzTable[lower >>> 24] + 24;
721:                } else {
722:                    // grab upper 32 bits
723:                    int upper = (int) (val >> 32);
724:                    lowByte = upper & 0xff;
725:                    if (lowByte != 0)
726:                        return ntzTable[lowByte] + 32;
727:                    lowByte = (upper >>> 8) & 0xff;
728:                    if (lowByte != 0)
729:                        return ntzTable[lowByte] + 40;
730:                    lowByte = (upper >>> 16) & 0xff;
731:                    if (lowByte != 0)
732:                        return ntzTable[lowByte] + 48;
733:                    // no need to mask off low byte for the last byte in the 32 bit word
734:                    // no need to check for zero on the last byte either.
735:                    return ntzTable[upper >>> 24] + 56;
736:                }
737:            }
738:
739:            /** returns 0 based index of first set bit
740:             * (only works for x!=0)
741:             * <br/> This is an alternate implementation of ntz()
742:             */
743:            public static int ntz2(long x) {
744:                int n = 0;
745:                int y = (int) x;
746:                if (y == 0) {
747:                    n += 32;
748:                    y = (int) (x >>> 32);
749:                } // the only 64 bit shift necessary
750:                if ((y & 0x0000FFFF) == 0) {
751:                    n += 16;
752:                    y >>>= 16;
753:                }
754:                if ((y & 0x000000FF) == 0) {
755:                    n += 8;
756:                    y >>>= 8;
757:                }
758:                return (ntzTable[y & 0xff]) + n;
759:            }
760:
761:            /** returns 0 based index of first set bit
762:             * <br/> This is an alternate implementation of ntz()
763:             */
764:            public static int ntz3(long x) {
765:                // another implementation taken from Hackers Delight, extended to 64 bits
766:                // and converted to Java.
767:                // Many 32 bit ntz algorithms are at http://www.hackersdelight.org/HDcode/ntz.cc
768:                int n = 1;
769:
770:                // do the first step as a long, all others as ints.
771:                int y = (int) x;
772:                if (y == 0) {
773:                    n += 32;
774:                    y = (int) (x >>> 32);
775:                }
776:                if ((y & 0x0000FFFF) == 0) {
777:                    n += 16;
778:                    y >>>= 16;
779:                }
780:                if ((y & 0x000000FF) == 0) {
781:                    n += 8;
782:                    y >>>= 8;
783:                }
784:                if ((y & 0x0000000F) == 0) {
785:                    n += 4;
786:                    y >>>= 4;
787:                }
788:                if ((y & 0x00000003) == 0) {
789:                    n += 2;
790:                    y >>>= 2;
791:                }
792:                return n - (y & 1);
793:            }
794:
795:            /** returns true if v is a power of two or zero*/
796:            public static boolean isPowerOfTwo(int v) {
797:                return ((v & (v - 1)) == 0);
798:            }
799:
800:            /** returns true if v is a power of two or zero*/
801:            public static boolean isPowerOfTwo(long v) {
802:                return ((v & (v - 1)) == 0);
803:            }
804:
805:            /** returns the next highest power of two, or the current value if it's already a power of two or zero*/
806:            public static int nextHighestPowerOfTwo(int v) {
807:                v--;
808:                v |= v >> 1;
809:                v |= v >> 2;
810:                v |= v >> 4;
811:                v |= v >> 8;
812:                v |= v >> 16;
813:                v++;
814:                return v;
815:            }
816:
817:            /** returns the next highest power of two, or the current value if it's already a power of two or zero*/
818:            public static long nextHighestPowerOfTwo(long v) {
819:                v--;
820:                v |= v >> 1;
821:                v |= v >> 2;
822:                v |= v >> 4;
823:                v |= v >> 8;
824:                v |= v >> 16;
825:                v |= v >> 32;
826:                v++;
827:                return v;
828:            }
829:
830:        }
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