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Merge pull request #8941 from pazis/BAEL3881 

BAEL-3881
This commit is contained in:
Josh Cummings 2020-03-23 09:57:17 -06:00 committed by GitHub
parent abd46c4349 0a48cad1c3
commit 8cfb3a1db8
4 changed files with 70 additions and 0 deletions
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15
algorithms-miscellaneous-6/pom.xml Normal file
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<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<artifactId>algorithms-miscellaneous-6</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>algorithms-miscellaneous-6</name>
<parent>
<groupId>com.baeldung</groupId>
<artifactId>parent-modules</artifactId>
<version>1.0.0-SNAPSHOT</version>
</parent>
</project>

33
algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/gradientdescent/GradientDescent.java Normal file
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package com.baeldung.algorithms.gradientdescent;
import java.util.function.Function;
public class GradientDescent {
private final double precision = 0.000001;
public double findLocalMinimum(Function<Double, Double> f, double initialX) {
double stepCoefficient = 0.1;
double previousStep = 1.0;
double currentX = initialX;
double previousX = initialX;
double previousY = f.apply(previousX);
int iter = 100;
currentX += stepCoefficient * previousY;
while (previousStep > precision && iter > 0) {
iter--;
double currentY = f.apply(currentX);
if (currentY > previousY) {
stepCoefficient = -stepCoefficient / 2;
}
previousX = currentX;
currentX += stepCoefficient * previousY;
previousY = currentY;
previousStep = StrictMath.abs(currentX - previousX);
}
return currentX;
}
}

20
algorithms-miscellaneous-6/src/test/java/com/baeldung/algorithms/gradientdescent/GradientDescentUnitTest.java Normal file
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package com.baeldung.algorithms.gradientdescent;
import static org.junit.Assert.assertTrue;
import java.util.function.Function;
import org.junit.Test;
public class GradientDescentUnitTest {
@Test
public void givenFunction_whenStartingPointIsOne_thenLocalMinimumIsFound() {
Function<Double, Double> df = x ->
StrictMath.abs(StrictMath.pow(x, 3)) - (3 * StrictMath.pow(x, 2)) + x;
GradientDescent gd = new GradientDescent();
double res = gd.findLocalMinimum(df, 1);
assertTrue(res > 1.78);
assertTrue(res < 1.84);
}
}

2
pom.xml
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@ -342,6 +342,7 @@
<module>algorithms-miscellaneous-3</module>
<module>algorithms-miscellaneous-4</module>
<module>algorithms-miscellaneous-5</module>
<module>algorithms-miscellaneous-6</module>
<module>algorithms-searching</module>
<module>algorithms-sorting</module>
<module>algorithms-sorting-2</module>
@ -853,6 +854,7 @@
<module>algorithms-miscellaneous-3</module>
<module>algorithms-miscellaneous-4</module>
<module>algorithms-miscellaneous-5</module>
<module>algorithms-miscellaneous-6</module>
<module>algorithms-searching</module>
<module>algorithms-sorting</module>
<module>algorithms-sorting-2</module>