/*
* 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);
}
}