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Lucene example source code file (TestBitUtil.java)

This example Lucene source code file (TestBitUtil.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Lucene tags/keywords

lucene-3197, lucene-3197, lucenetestcase, lucenetestcase, see, see, testbitutil, testbitutil

The Lucene TestBitUtil.java source code

/**
 * 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;

public class TestBitUtil extends LuceneTestCase {

  private static int slowNlz(long x) {
    if (x == 0L) return 64;
    int nlz = 0;
    while ( ((x << nlz) & (1L << 63)) == 0) {
      nlz++;
    }
    return nlz;
  }

  private void checkNlz(long x) {
    assertEquals(slowNlz(x), BitUtil.nlz(x));
    assertEquals(Long.numberOfLeadingZeros(x), BitUtil.nlz(x));
  }
  
  public void testNlz() {
    checkNlz(0L);
    checkNlz(1L);
    checkNlz(-1L);
    for (int i = 1; i <= 63; i++) {
      checkNlz(1L << i);
      checkNlz((1L << i) + (1L << (i>>1)));
    }
  }

  public void testBitUtils() {
    long num = 100000;
    assertEquals( 5, BitUtil.ntz(num) );
    assertEquals( 5, BitUtil.ntz2(num) );
    assertEquals( 5, BitUtil.ntz3(num) );
    
    num = 10;
    assertEquals( 1, BitUtil.ntz(num) );
    assertEquals( 1, BitUtil.ntz2(num) );
    assertEquals( 1, BitUtil.ntz3(num) );

    for (int i=0; i<64; i++) {
      num = 1L << i;
      assertEquals( i, BitUtil.ntz(num) );
      assertEquals( i, BitUtil.ntz2(num) );
      assertEquals( i, BitUtil.ntz3(num) );
    }
  }


  private long testArg(int shift) {
    return (1L << shift) + (1L << (shift>>1));
  }
  
  private long nlzBitUtilBasicLoop(int iters) {
    long sumRes = 0;
    while (iters-- >= 0) {
      for (int i = 1; i <= 63; i++) {
      	long a = testArg(i);
	sumRes += BitUtil.nlz(a);
	sumRes += BitUtil.nlz(a+1);
	sumRes += BitUtil.nlz(a-1);
	sumRes += BitUtil.nlz(a+10);
	sumRes += BitUtil.nlz(a-10);
      }
    }
    return sumRes;
  }
    
  private long nlzLongBasicLoop(int iters) {
    long sumRes = 0;
    while (iters-- >= 0) {
      for (int i = 1; i <= 63; i++) {
      	long a = testArg(i);
	sumRes += Long.numberOfLeadingZeros(a);
	sumRes += Long.numberOfLeadingZeros(a+1);
	sumRes += Long.numberOfLeadingZeros(a-1);
	sumRes += Long.numberOfLeadingZeros(a+10);
	sumRes += Long.numberOfLeadingZeros(a-10);
      }
    }
    return sumRes;
  }

  public void tstPerfNlz() { // See LUCENE-3197, prefer to use Long.numberOfLeadingZeros() over BitUtil.nlz().
    final long measureMilliSecs = 2000;
    final int basicIters = 100000;
    long startTime;
    long endTime;
    long curTime;
    long dummy = 0; // avoid optimizing away

    dummy = 0;
    int bitUtilLoops = 0;
    startTime = System.currentTimeMillis();
    endTime = startTime + measureMilliSecs;
    do {
      dummy += nlzBitUtilBasicLoop(basicIters);
      bitUtilLoops++;
      curTime = System.currentTimeMillis();
    } while (curTime < endTime);
    int bitUtilPsTime = (int) (1000000000 * (curTime - startTime) / (basicIters * 5 * 63 * (float) bitUtilLoops));
    System.out.println("BitUtil nlz time: " + (bitUtilPsTime/1) + " picosec/call, dummy: " + dummy);


    dummy = 0;
    int longLoops = 0;
    startTime = System.currentTimeMillis();
    endTime = startTime + measureMilliSecs;
    do {
      dummy += nlzLongBasicLoop(basicIters);
      longLoops++;
      curTime = System.currentTimeMillis();
    } while (curTime < endTime);
    int longPsTime = (int) (1000000000 * (curTime - startTime) / (basicIters * 5 * 63 * (float) longLoops));
    System.out.println("Long    nlz time: " + longPsTime + " picosec/call, dummy: " + dummy);
  }
}

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