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sazzer
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Examples for Branch Prediction article (eugenp#8426)
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‎core-java-modules/core-java-perf/src/test/java/com/baeldung/branchprediction/CombiningUnitTest.java‎

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package com.baeldung.branchprediction;
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import java.util.stream.LongStream;
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import org.junit.Test;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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public class CombiningUnitTest {
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private static final Logger LOG = LoggerFactory.getLogger(CombiningUnitTest.class);
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public static final int TOP = 10000000;
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public static final double FRACTION = 0.1;
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@Test
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public void combined() {
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long[] first = LongStream.range(0, TOP)
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.map(n -> Math.random() < FRACTION ? 0 : n)
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.toArray();
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long[] second = LongStream.range(0, TOP)
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.map(n -> Math.random() < FRACTION ? 0 : n)
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.toArray();
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long count = 0;
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long start = System.currentTimeMillis();
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for (int i = 0; i < TOP; i++) {
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if (first[i] * second[i] != 0) {
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++count;
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}
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}
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long end = System.currentTimeMillis();
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LOG.info("Counted {}/{} numbers using combined mode in {}ms", count, TOP, end - start);
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}
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@Test
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public void separate() {
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long[] first = LongStream.range(0, TOP)
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.map(n -> Math.random() < FRACTION ? 0 : n)
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.toArray();
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long[] second = LongStream.range(0, TOP)
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.map(n -> Math.random() < FRACTION ? 0 : n)
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.toArray();
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long count = 0;
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long start = System.currentTimeMillis();
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for (int i = 0; i < TOP; i++) {
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if (first[i] != 0 && second[i] != 0) {
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++count;
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}
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}
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long end = System.currentTimeMillis();
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LOG.info("Counted {}/{} numbers using separate mode in {}ms", count, TOP, end - start);
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}
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}

‎core-java-modules/core-java-perf/src/test/java/com/baeldung/branchprediction/IfUnitTest.java‎

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package com.baeldung.branchprediction;
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import java.util.Collections;
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import java.util.List;
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import java.util.stream.Collectors;
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import java.util.stream.LongStream;
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import org.junit.Test;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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public class IfUnitTest {
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private static final Logger LOG = LoggerFactory.getLogger(IfUnitTest.class);
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public static final int TOP = 10000000;
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@Test
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public void majorBranchSorted() {
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test(TOP, 0.9, false);
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}
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@Test
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public void minorBranchSorted() {
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test(TOP, 0.1, false);
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}
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@Test
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public void equalBranchSorted() {
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test(TOP, 0.5, false);
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}
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@Test
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public void allBranchSorted() {
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test(TOP, 1, false);
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}
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@Test
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public void noneBranchSorted() {
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test(TOP, 0, false);
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}
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@Test
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public void majorBranchShuffled() {
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test(TOP, 0.9, true);
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}
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@Test
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public void minorBranchShuffled() {
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test(TOP, 0.1, true);
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}
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@Test
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public void equalBranchShuffled() {
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test(TOP, 0.5, true);
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}
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@Test
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public void allBranchShuffled() {
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test(TOP, 1, true);
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}
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@Test
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public void noneBranchShuffled() {
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test(TOP, 0, true);
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}
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private void test(long top, double cutoffPercentage, boolean shuffle) {
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List<Long> numbers = LongStream.range(0, top)
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.boxed()
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.collect(Collectors.toList());
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if (shuffle) {
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Collections.shuffle(numbers);
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}
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long cutoff = (long)(top * cutoffPercentage);
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long low = 0;
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long high = 0;
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long start = System.currentTimeMillis();
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for (Long number : numbers) {
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if (number < cutoff) {
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++low;
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} else {
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++high;
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}
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}
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long end = System.currentTimeMillis();
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LOG.info("Counted {}/{} {} numbers in {}ms", low, high, shuffle ? "shuffled" : "sorted", end - start);
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}
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}

‎core-java-modules/core-java-perf/src/test/java/com/baeldung/branchprediction/SortingUnitTest.java‎

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package com.baeldung.branchprediction;
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import java.util.Collections;
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import java.util.List;
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import java.util.stream.Collectors;
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import java.util.stream.LongStream;
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import org.junit.Test;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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public class SortingUnitTest {
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private static final Logger LOG = LoggerFactory.getLogger(SortingUnitTest.class);
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public static final int BIG = 10000000;
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public static final int SMALL = 100000;
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@Test
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public void sortedBig() {
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test(BIG, false);
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}
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@Test
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public void shuffledBig() {
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test(BIG, true);
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}
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@Test
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public void sortedSmall() {
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test(SMALL, false);
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}
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@Test
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public void shuffledSmall() {
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test(SMALL, true);
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}
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private void test(long top, boolean shuffle) {
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List<Long> numbers = LongStream.range(0, top)
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.boxed()
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.collect(Collectors.toList());
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if (shuffle) {
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Collections.shuffle(numbers);
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}
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long cutoff = top / 2;
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long count = 0;
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long start = System.currentTimeMillis();
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for (Long number : numbers) {
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if (number < cutoff) {
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++count;
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}
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}
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long end = System.currentTimeMillis();
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LOG.info("Counted {}/{} {} numbers in {}ms",
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count, top, shuffle ? "shuffled" : "sorted", end - start);
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}
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}

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