+++ /dev/null
-/**
- * Licensed to the Apache Software Foundation (ASF) under one or more
- * contributor license agreements. See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The ASF licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License. You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package org.apache.lucene.util; // from org.apache.solr.util rev 555343
-
-/** A variety of high efficiency bit twiddling routines.
- * @lucene.internal
- */
-public final class BitUtil {
-
- private BitUtil() {} // no instance
-
- /** Returns the number of bits set in the long */
- public static int pop(long x) {
- /* Hacker's Delight 32 bit pop function:
- * http://www.hackersdelight.org/HDcode/newCode/pop_arrayHS.cc
- *
- int pop(unsigned x) {
- x = x - ((x >> 1) & 0x55555555);
- x = (x & 0x33333333) + ((x >> 2) & 0x33333333);
- x = (x + (x >> 4)) & 0x0F0F0F0F;
- x = x + (x >> 8);
- x = x + (x >> 16);
- return x & 0x0000003F;
- }
- ***/
-
- // 64 bit java version of the C function from above
- x = x - ((x >>> 1) & 0x5555555555555555L);
- x = (x & 0x3333333333333333L) + ((x >>>2 ) & 0x3333333333333333L);
- x = (x + (x >>> 4)) & 0x0F0F0F0F0F0F0F0FL;
- x = x + (x >>> 8);
- x = x + (x >>> 16);
- x = x + (x >>> 32);
- return ((int)x) & 0x7F;
- }
-
- /*** Returns the number of set bits in an array of longs. */
- public static long pop_array(long A[], int wordOffset, int numWords) {
- /*
- * Robert Harley and David Seal's bit counting algorithm, as documented
- * in the revisions of Hacker's Delight
- * http://www.hackersdelight.org/revisions.pdf
- * http://www.hackersdelight.org/HDcode/newCode/pop_arrayHS.cc
- *
- * This function was adapted to Java, and extended to use 64 bit words.
- * if only we had access to wider registers like SSE from java...
- *
- * This function can be transformed to compute the popcount of other functions
- * on bitsets via something like this:
- * sed 's/A\[\([^]]*\)\]/\(A[\1] \& B[\1]\)/g'
- *
- */
- int n = wordOffset+numWords;
- long tot=0, tot8=0;
- long ones=0, twos=0, fours=0;
-
- int i;
- for (i = wordOffset; i <= n - 8; i+=8) {
- /*** C macro from Hacker's Delight
- #define CSA(h,l, a,b,c) \
- {unsigned u = a ^ b; unsigned v = c; \
- h = (a & b) | (u & v); l = u ^ v;}
- ***/
-
- long twosA,twosB,foursA,foursB,eights;
-
- // CSA(twosA, ones, ones, A[i], A[i+1])
- {
- long b=A[i], c=A[i+1];
- long u=ones ^ b;
- twosA=(ones & b)|( u & c);
- ones=u^c;
- }
- // CSA(twosB, ones, ones, A[i+2], A[i+3])
- {
- long b=A[i+2], c=A[i+3];
- long u=ones^b;
- twosB =(ones&b)|(u&c);
- ones=u^c;
- }
- //CSA(foursA, twos, twos, twosA, twosB)
- {
- long u=twos^twosA;
- foursA=(twos&twosA)|(u&twosB);
- twos=u^twosB;
- }
- //CSA(twosA, ones, ones, A[i+4], A[i+5])
- {
- long b=A[i+4], c=A[i+5];
- long u=ones^b;
- twosA=(ones&b)|(u&c);
- ones=u^c;
- }
- // CSA(twosB, ones, ones, A[i+6], A[i+7])
- {
- long b=A[i+6], c=A[i+7];
- long u=ones^b;
- twosB=(ones&b)|(u&c);
- ones=u^c;
- }
- //CSA(foursB, twos, twos, twosA, twosB)
- {
- long u=twos^twosA;
- foursB=(twos&twosA)|(u&twosB);
- twos=u^twosB;
- }
-
- //CSA(eights, fours, fours, foursA, foursB)
- {
- long u=fours^foursA;
- eights=(fours&foursA)|(u&foursB);
- fours=u^foursB;
- }
- tot8 += pop(eights);
- }
-
- // handle trailing words in a binary-search manner...
- // derived from the loop above by setting specific elements to 0.
- // the original method in Hackers Delight used a simple for loop:
- // for (i = i; i < n; i++) // Add in the last elements
- // tot = tot + pop(A[i]);
-
- if (i<=n-4) {
- long twosA, twosB, foursA, eights;
- {
- long b=A[i], c=A[i+1];
- long u=ones ^ b;
- twosA=(ones & b)|( u & c);
- ones=u^c;
- }
- {
- long b=A[i+2], c=A[i+3];
- long u=ones^b;
- twosB =(ones&b)|(u&c);
- ones=u^c;
- }
- {
- long u=twos^twosA;
- foursA=(twos&twosA)|(u&twosB);
- twos=u^twosB;
- }
- eights=fours&foursA;
- fours=fours^foursA;
-
- tot8 += pop(eights);
- i+=4;
- }
-
- if (i<=n-2) {
- long b=A[i], c=A[i+1];
- long u=ones ^ b;
- long twosA=(ones & b)|( u & c);
- ones=u^c;
-
- long foursA=twos&twosA;
- twos=twos^twosA;
-
- long eights=fours&foursA;
- fours=fours^foursA;
-
- tot8 += pop(eights);
- i+=2;
- }
-
- if (i<n) {
- tot += pop(A[i]);
- }
-
- tot += (pop(fours)<<2)
- + (pop(twos)<<1)
- + pop(ones)
- + (tot8<<3);
-
- return tot;
- }
-
- /** Returns the popcount or cardinality of the two sets after an intersection.
- * Neither array is modified.
- */
- public static long pop_intersect(long A[], long B[], int wordOffset, int numWords) {
- // generated from pop_array via sed 's/A\[\([^]]*\)\]/\(A[\1] \& B[\1]\)/g'
- int n = wordOffset+numWords;
- long tot=0, tot8=0;
- long ones=0, twos=0, fours=0;
-
- int i;
- for (i = wordOffset; i <= n - 8; i+=8) {
- long twosA,twosB,foursA,foursB,eights;
-
- // CSA(twosA, ones, ones, (A[i] & B[i]), (A[i+1] & B[i+1]))
- {
- long b=(A[i] & B[i]), c=(A[i+1] & B[i+1]);
- long u=ones ^ b;
- twosA=(ones & b)|( u & c);
- ones=u^c;
- }
- // CSA(twosB, ones, ones, (A[i+2] & B[i+2]), (A[i+3] & B[i+3]))
- {
- long b=(A[i+2] & B[i+2]), c=(A[i+3] & B[i+3]);
- long u=ones^b;
- twosB =(ones&b)|(u&c);
- ones=u^c;
- }
- //CSA(foursA, twos, twos, twosA, twosB)
- {
- long u=twos^twosA;
- foursA=(twos&twosA)|(u&twosB);
- twos=u^twosB;
- }
- //CSA(twosA, ones, ones, (A[i+4] & B[i+4]), (A[i+5] & B[i+5]))
- {
- long b=(A[i+4] & B[i+4]), c=(A[i+5] & B[i+5]);
- long u=ones^b;
- twosA=(ones&b)|(u&c);
- ones=u^c;
- }
- // CSA(twosB, ones, ones, (A[i+6] & B[i+6]), (A[i+7] & B[i+7]))
- {
- long b=(A[i+6] & B[i+6]), c=(A[i+7] & B[i+7]);
- long u=ones^b;
- twosB=(ones&b)|(u&c);
- ones=u^c;
- }
- //CSA(foursB, twos, twos, twosA, twosB)
- {
- long u=twos^twosA;
- foursB=(twos&twosA)|(u&twosB);
- twos=u^twosB;
- }
-
- //CSA(eights, fours, fours, foursA, foursB)
- {
- long u=fours^foursA;
- eights=(fours&foursA)|(u&foursB);
- fours=u^foursB;
- }
- tot8 += pop(eights);
- }
-
-
- if (i<=n-4) {
- long twosA, twosB, foursA, eights;
- {
- long b=(A[i] & B[i]), c=(A[i+1] & B[i+1]);
- long u=ones ^ b;
- twosA=(ones & b)|( u & c);
- ones=u^c;
- }
- {
- long b=(A[i+2] & B[i+2]), c=(A[i+3] & B[i+3]);
- long u=ones^b;
- twosB =(ones&b)|(u&c);
- ones=u^c;
- }
- {
- long u=twos^twosA;
- foursA=(twos&twosA)|(u&twosB);
- twos=u^twosB;
- }
- eights=fours&foursA;
- fours=fours^foursA;
-
- tot8 += pop(eights);
- i+=4;
- }
-
- if (i<=n-2) {
- long b=(A[i] & B[i]), c=(A[i+1] & B[i+1]);
- long u=ones ^ b;
- long twosA=(ones & b)|( u & c);
- ones=u^c;
-
- long foursA=twos&twosA;
- twos=twos^twosA;
-
- long eights=fours&foursA;
- fours=fours^foursA;
-
- tot8 += pop(eights);
- i+=2;
- }
-
- if (i<n) {
- tot += pop((A[i] & B[i]));
- }
-
- tot += (pop(fours)<<2)
- + (pop(twos)<<1)
- + pop(ones)
- + (tot8<<3);
-
- return tot;
- }
-
- /** Returns the popcount or cardinality of the union of two sets.
- * Neither array is modified.
- */
- public static long pop_union(long A[], long B[], int wordOffset, int numWords) {
- // generated from pop_array via sed 's/A\[\([^]]*\)\]/\(A[\1] \| B[\1]\)/g'
- int n = wordOffset+numWords;
- long tot=0, tot8=0;
- long ones=0, twos=0, fours=0;
-
- int i;
- for (i = wordOffset; i <= n - 8; i+=8) {
- /*** C macro from Hacker's Delight
- #define CSA(h,l, a,b,c) \
- {unsigned u = a ^ b; unsigned v = c; \
- h = (a & b) | (u & v); l = u ^ v;}
- ***/
-
- long twosA,twosB,foursA,foursB,eights;
-
- // CSA(twosA, ones, ones, (A[i] | B[i]), (A[i+1] | B[i+1]))
- {
- long b=(A[i] | B[i]), c=(A[i+1] | B[i+1]);
- long u=ones ^ b;
- twosA=(ones & b)|( u & c);
- ones=u^c;
- }
- // CSA(twosB, ones, ones, (A[i+2] | B[i+2]), (A[i+3] | B[i+3]))
- {
- long b=(A[i+2] | B[i+2]), c=(A[i+3] | B[i+3]);
- long u=ones^b;
- twosB =(ones&b)|(u&c);
- ones=u^c;
- }
- //CSA(foursA, twos, twos, twosA, twosB)
- {
- long u=twos^twosA;
- foursA=(twos&twosA)|(u&twosB);
- twos=u^twosB;
- }
- //CSA(twosA, ones, ones, (A[i+4] | B[i+4]), (A[i+5] | B[i+5]))
- {
- long b=(A[i+4] | B[i+4]), c=(A[i+5] | B[i+5]);
- long u=ones^b;
- twosA=(ones&b)|(u&c);
- ones=u^c;
- }
- // CSA(twosB, ones, ones, (A[i+6] | B[i+6]), (A[i+7] | B[i+7]))
- {
- long b=(A[i+6] | B[i+6]), c=(A[i+7] | B[i+7]);
- long u=ones^b;
- twosB=(ones&b)|(u&c);
- ones=u^c;
- }
- //CSA(foursB, twos, twos, twosA, twosB)
- {
- long u=twos^twosA;
- foursB=(twos&twosA)|(u&twosB);
- twos=u^twosB;
- }
-
- //CSA(eights, fours, fours, foursA, foursB)
- {
- long u=fours^foursA;
- eights=(fours&foursA)|(u&foursB);
- fours=u^foursB;
- }
- tot8 += pop(eights);
- }
-
-
- if (i<=n-4) {
- long twosA, twosB, foursA, eights;
- {
- long b=(A[i] | B[i]), c=(A[i+1] | B[i+1]);
- long u=ones ^ b;
- twosA=(ones & b)|( u & c);
- ones=u^c;
- }
- {
- long b=(A[i+2] | B[i+2]), c=(A[i+3] | B[i+3]);
- long u=ones^b;
- twosB =(ones&b)|(u&c);
- ones=u^c;
- }
- {
- long u=twos^twosA;
- foursA=(twos&twosA)|(u&twosB);
- twos=u^twosB;
- }
- eights=fours&foursA;
- fours=fours^foursA;
-
- tot8 += pop(eights);
- i+=4;
- }
-
- if (i<=n-2) {
- long b=(A[i] | B[i]), c=(A[i+1] | B[i+1]);
- long u=ones ^ b;
- long twosA=(ones & b)|( u & c);
- ones=u^c;
-
- long foursA=twos&twosA;
- twos=twos^twosA;
-
- long eights=fours&foursA;
- fours=fours^foursA;
-
- tot8 += pop(eights);
- i+=2;
- }
-
- if (i<n) {
- tot += pop((A[i] | B[i]));
- }
-
- tot += (pop(fours)<<2)
- + (pop(twos)<<1)
- + pop(ones)
- + (tot8<<3);
-
- return tot;
- }
-
- /** Returns the popcount or cardinality of A & ~B
- * Neither array is modified.
- */
- public static long pop_andnot(long A[], long B[], int wordOffset, int numWords) {
- // generated from pop_array via sed 's/A\[\([^]]*\)\]/\(A[\1] \& ~B[\1]\)/g'
- int n = wordOffset+numWords;
- long tot=0, tot8=0;
- long ones=0, twos=0, fours=0;
-
- int i;
- for (i = wordOffset; i <= n - 8; i+=8) {
- /*** C macro from Hacker's Delight
- #define CSA(h,l, a,b,c) \
- {unsigned u = a ^ b; unsigned v = c; \
- h = (a & b) | (u & v); l = u ^ v;}
- ***/
-
- long twosA,twosB,foursA,foursB,eights;
-
- // CSA(twosA, ones, ones, (A[i] & ~B[i]), (A[i+1] & ~B[i+1]))
- {
- long b=(A[i] & ~B[i]), c=(A[i+1] & ~B[i+1]);
- long u=ones ^ b;
- twosA=(ones & b)|( u & c);
- ones=u^c;
- }
- // CSA(twosB, ones, ones, (A[i+2] & ~B[i+2]), (A[i+3] & ~B[i+3]))
- {
- long b=(A[i+2] & ~B[i+2]), c=(A[i+3] & ~B[i+3]);
- long u=ones^b;
- twosB =(ones&b)|(u&c);
- ones=u^c;
- }
- //CSA(foursA, twos, twos, twosA, twosB)
- {
- long u=twos^twosA;
- foursA=(twos&twosA)|(u&twosB);
- twos=u^twosB;
- }
- //CSA(twosA, ones, ones, (A[i+4] & ~B[i+4]), (A[i+5] & ~B[i+5]))
- {
- long b=(A[i+4] & ~B[i+4]), c=(A[i+5] & ~B[i+5]);
- long u=ones^b;
- twosA=(ones&b)|(u&c);
- ones=u^c;
- }
- // CSA(twosB, ones, ones, (A[i+6] & ~B[i+6]), (A[i+7] & ~B[i+7]))
- {
- long b=(A[i+6] & ~B[i+6]), c=(A[i+7] & ~B[i+7]);
- long u=ones^b;
- twosB=(ones&b)|(u&c);
- ones=u^c;
- }
- //CSA(foursB, twos, twos, twosA, twosB)
- {
- long u=twos^twosA;
- foursB=(twos&twosA)|(u&twosB);
- twos=u^twosB;
- }
-
- //CSA(eights, fours, fours, foursA, foursB)
- {
- long u=fours^foursA;
- eights=(fours&foursA)|(u&foursB);
- fours=u^foursB;
- }
- tot8 += pop(eights);
- }
-
-
- if (i<=n-4) {
- long twosA, twosB, foursA, eights;
- {
- long b=(A[i] & ~B[i]), c=(A[i+1] & ~B[i+1]);
- long u=ones ^ b;
- twosA=(ones & b)|( u & c);
- ones=u^c;
- }
- {
- long b=(A[i+2] & ~B[i+2]), c=(A[i+3] & ~B[i+3]);
- long u=ones^b;
- twosB =(ones&b)|(u&c);
- ones=u^c;
- }
- {
- long u=twos^twosA;
- foursA=(twos&twosA)|(u&twosB);
- twos=u^twosB;
- }
- eights=fours&foursA;
- fours=fours^foursA;
-
- tot8 += pop(eights);
- i+=4;
- }
-
- if (i<=n-2) {
- long b=(A[i] & ~B[i]), c=(A[i+1] & ~B[i+1]);
- long u=ones ^ b;
- long twosA=(ones & b)|( u & c);
- ones=u^c;
-
- long foursA=twos&twosA;
- twos=twos^twosA;
-
- long eights=fours&foursA;
- fours=fours^foursA;
-
- tot8 += pop(eights);
- i+=2;
- }
-
- if (i<n) {
- tot += pop((A[i] & ~B[i]));
- }
-
- tot += (pop(fours)<<2)
- + (pop(twos)<<1)
- + pop(ones)
- + (tot8<<3);
-
- return tot;
- }
-
- public static long pop_xor(long A[], long B[], int wordOffset, int numWords) {
- int n = wordOffset+numWords;
- long tot=0, tot8=0;
- long ones=0, twos=0, fours=0;
-
- int i;
- for (i = wordOffset; i <= n - 8; i+=8) {
- /*** C macro from Hacker's Delight
- #define CSA(h,l, a,b,c) \
- {unsigned u = a ^ b; unsigned v = c; \
- h = (a & b) | (u & v); l = u ^ v;}
- ***/
-
- long twosA,twosB,foursA,foursB,eights;
-
- // CSA(twosA, ones, ones, (A[i] ^ B[i]), (A[i+1] ^ B[i+1]))
- {
- long b=(A[i] ^ B[i]), c=(A[i+1] ^ B[i+1]);
- long u=ones ^ b;
- twosA=(ones & b)|( u & c);
- ones=u^c;
- }
- // CSA(twosB, ones, ones, (A[i+2] ^ B[i+2]), (A[i+3] ^ B[i+3]))
- {
- long b=(A[i+2] ^ B[i+2]), c=(A[i+3] ^ B[i+3]);
- long u=ones^b;
- twosB =(ones&b)|(u&c);
- ones=u^c;
- }
- //CSA(foursA, twos, twos, twosA, twosB)
- {
- long u=twos^twosA;
- foursA=(twos&twosA)|(u&twosB);
- twos=u^twosB;
- }
- //CSA(twosA, ones, ones, (A[i+4] ^ B[i+4]), (A[i+5] ^ B[i+5]))
- {
- long b=(A[i+4] ^ B[i+4]), c=(A[i+5] ^ B[i+5]);
- long u=ones^b;
- twosA=(ones&b)|(u&c);
- ones=u^c;
- }
- // CSA(twosB, ones, ones, (A[i+6] ^ B[i+6]), (A[i+7] ^ B[i+7]))
- {
- long b=(A[i+6] ^ B[i+6]), c=(A[i+7] ^ B[i+7]);
- long u=ones^b;
- twosB=(ones&b)|(u&c);
- ones=u^c;
- }
- //CSA(foursB, twos, twos, twosA, twosB)
- {
- long u=twos^twosA;
- foursB=(twos&twosA)|(u&twosB);
- twos=u^twosB;
- }
-
- //CSA(eights, fours, fours, foursA, foursB)
- {
- long u=fours^foursA;
- eights=(fours&foursA)|(u&foursB);
- fours=u^foursB;
- }
- tot8 += pop(eights);
- }
-
-
- if (i<=n-4) {
- long twosA, twosB, foursA, eights;
- {
- long b=(A[i] ^ B[i]), c=(A[i+1] ^ B[i+1]);
- long u=ones ^ b;
- twosA=(ones & b)|( u & c);
- ones=u^c;
- }
- {
- long b=(A[i+2] ^ B[i+2]), c=(A[i+3] ^ B[i+3]);
- long u=ones^b;
- twosB =(ones&b)|(u&c);
- ones=u^c;
- }
- {
- long u=twos^twosA;
- foursA=(twos&twosA)|(u&twosB);
- twos=u^twosB;
- }
- eights=fours&foursA;
- fours=fours^foursA;
-
- tot8 += pop(eights);
- i+=4;
- }
-
- if (i<=n-2) {
- long b=(A[i] ^ B[i]), c=(A[i+1] ^ B[i+1]);
- long u=ones ^ b;
- long twosA=(ones & b)|( u & c);
- ones=u^c;
-
- long foursA=twos&twosA;
- twos=twos^twosA;
-
- long eights=fours&foursA;
- fours=fours^foursA;
-
- tot8 += pop(eights);
- i+=2;
- }
-
- if (i<n) {
- tot += pop((A[i] ^ B[i]));
- }
-
- tot += (pop(fours)<<2)
- + (pop(twos)<<1)
- + pop(ones)
- + (tot8<<3);
-
- return tot;
- }
-
- /* python code to generate ntzTable
- def ntz(val):
- if val==0: return 8
- i=0
- while (val&0x01)==0:
- i = i+1
- val >>= 1
- return i
- print ','.join([ str(ntz(i)) for i in range(256) ])
- ***/
- /** table of number of trailing zeros in a byte */
- public static final byte[] ntzTable = {8,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,5,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,6,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,5,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,7,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,5,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,6,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,5,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0};
-
-
- /** Returns number of trailing zeros in a 64 bit long value. */
- public static int ntz(long val) {
- // A full binary search to determine the low byte was slower than
- // a linear search for nextSetBit(). This is most likely because
- // the implementation of nextSetBit() shifts bits to the right, increasing
- // the probability that the first non-zero byte is in the rhs.
- //
- // This implementation does a single binary search at the top level only
- // so that all other bit shifting can be done on ints instead of longs to
- // remain friendly to 32 bit architectures. In addition, the case of a
- // non-zero first byte is checked for first because it is the most common
- // in dense bit arrays.
-
- int lower = (int)val;
- int lowByte = lower & 0xff;
- if (lowByte != 0) return ntzTable[lowByte];
-
- if (lower!=0) {
- lowByte = (lower>>>8) & 0xff;
- if (lowByte != 0) return ntzTable[lowByte] + 8;
- lowByte = (lower>>>16) & 0xff;
- if (lowByte != 0) return ntzTable[lowByte] + 16;
- // no need to mask off low byte for the last byte in the 32 bit word
- // no need to check for zero on the last byte either.
- return ntzTable[lower>>>24] + 24;
- } else {
- // grab upper 32 bits
- int upper=(int)(val>>32);
- lowByte = upper & 0xff;
- if (lowByte != 0) return ntzTable[lowByte] + 32;
- lowByte = (upper>>>8) & 0xff;
- if (lowByte != 0) return ntzTable[lowByte] + 40;
- lowByte = (upper>>>16) & 0xff;
- if (lowByte != 0) return ntzTable[lowByte] + 48;
- // no need to mask off low byte for the last byte in the 32 bit word
- // no need to check for zero on the last byte either.
- return ntzTable[upper>>>24] + 56;
- }
- }
-
- /** Returns number of trailing zeros in a 32 bit int value. */
- public static int ntz(int val) {
- // This implementation does a single binary search at the top level only.
- // In addition, the case of a non-zero first byte is checked for first
- // because it is the most common in dense bit arrays.
-
- int lowByte = val & 0xff;
- if (lowByte != 0) return ntzTable[lowByte];
- lowByte = (val>>>8) & 0xff;
- if (lowByte != 0) return ntzTable[lowByte] + 8;
- lowByte = (val>>>16) & 0xff;
- if (lowByte != 0) return ntzTable[lowByte] + 16;
- // no need to mask off low byte for the last byte.
- // no need to check for zero on the last byte either.
- return ntzTable[val>>>24] + 24;
- }
-
- /** returns 0 based index of first set bit
- * (only works for x!=0)
- * <br/> This is an alternate implementation of ntz()
- */
- public static int ntz2(long x) {
- int n = 0;
- int y = (int)x;
- if (y==0) {n+=32; y = (int)(x>>>32); } // the only 64 bit shift necessary
- if ((y & 0x0000FFFF) == 0) { n+=16; y>>>=16; }
- if ((y & 0x000000FF) == 0) { n+=8; y>>>=8; }
- return (ntzTable[ y & 0xff ]) + n;
- }
-
- /** returns 0 based index of first set bit
- * <br/> This is an alternate implementation of ntz()
- */
- public static int ntz3(long x) {
- // another implementation taken from Hackers Delight, extended to 64 bits
- // and converted to Java.
- // Many 32 bit ntz algorithms are at http://www.hackersdelight.org/HDcode/ntz.cc
- int n = 1;
-
- // do the first step as a long, all others as ints.
- int y = (int)x;
- if (y==0) {n+=32; y = (int)(x>>>32); }
- if ((y & 0x0000FFFF) == 0) { n+=16; y>>>=16; }
- if ((y & 0x000000FF) == 0) { n+=8; y>>>=8; }
- if ((y & 0x0000000F) == 0) { n+=4; y>>>=4; }
- if ((y & 0x00000003) == 0) { n+=2; y>>>=2; }
- return n - (y & 1);
- }
-
- /** table of number of leading zeros in a byte */
- public static final byte[] nlzTable = {8,7,6,6,5,5,5,5,4,4,4,4,4,4,4,4,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
-
- /** Returns the number of leading zero bits.
- */
- public static int nlz(long x) {
- int n = 0;
- // do the first step as a long
- int y = (int)(x>>>32);
- if (y==0) {n+=32; y = (int)(x); }
- if ((y & 0xFFFF0000) == 0) { n+=16; y<<=16; }
- if ((y & 0xFF000000) == 0) { n+=8; y<<=8; }
- return n + nlzTable[y >>> 24];
- /* implementation without table:
- if ((y & 0xF0000000) == 0) { n+=4; y<<=4; }
- if ((y & 0xC0000000) == 0) { n+=2; y<<=2; }
- if ((y & 0x80000000) == 0) { n+=1; y<<=1; }
- if ((y & 0x80000000) == 0) { n+=1;}
- return n;
- */
- }
-
-
- /** returns true if v is a power of two or zero*/
- public static boolean isPowerOfTwo(int v) {
- return ((v & (v-1)) == 0);
- }
-
- /** returns true if v is a power of two or zero*/
- public static boolean isPowerOfTwo(long v) {
- return ((v & (v-1)) == 0);
- }
-
- /** returns the next highest power of two, or the current value if it's already a power of two or zero*/
- public static int nextHighestPowerOfTwo(int v) {
- v--;
- v |= v >> 1;
- v |= v >> 2;
- v |= v >> 4;
- v |= v >> 8;
- v |= v >> 16;
- v++;
- return v;
- }
-
- /** returns the next highest power of two, or the current value if it's already a power of two or zero*/
- public static long nextHighestPowerOfTwo(long v) {
- v--;
- v |= v >> 1;
- v |= v >> 2;
- v |= v >> 4;
- v |= v >> 8;
- v |= v >> 16;
- v |= v >> 32;
- v++;
- return v;
- }
-
-}
fnp / pylucene.git / blobdiff