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Java example source code file (SincTest.java)

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

Learn more about this Java project at its project page.

Java - Java tags/keywords

derivativestructure, dfp, sinc, sinctest, test, univariatefunction

The SincTest.java Java example 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.commons.math3.analysis.function;

import org.apache.commons.math3.analysis.UnivariateFunction;
import org.apache.commons.math3.analysis.differentiation.DerivativeStructure;
import org.apache.commons.math3.dfp.Dfp;
import org.apache.commons.math3.dfp.DfpField;
import org.apache.commons.math3.dfp.DfpMath;
import org.apache.commons.math3.util.FastMath;
import org.junit.Assert;
import org.junit.Test;

public class SincTest {

   @Test
   public void testShortcut() {
       final Sinc s = new Sinc();
       final UnivariateFunction f = new UnivariateFunction() {
           public double value(double x) {
               Dfp dfpX = new DfpField(25).newDfp(x);
               return DfpMath.sin(dfpX).divide(dfpX).toDouble();
           }
       };

       for (double x = 1e-30; x < 1e10; x *= 2) {
           final double fX = f.value(x);
           final double sX = s.value(x);
           Assert.assertEquals("x=" + x, fX, sX, 2.0e-16);
       }
   }

   @Test
   public void testCrossings() {
       final Sinc s = new Sinc(true);
       final int numCrossings = 1000;
       final double tol = 2e-16;
       for (int i = 1; i <= numCrossings; i++) {
           Assert.assertEquals("i=" + i, 0, s.value(i), tol);
       }
   }

   @Test
   public void testZero() {
       final Sinc s = new Sinc();
       Assert.assertEquals(1d, s.value(0), 0);
   }

   @Test
   public void testEuler() {
       final Sinc s = new Sinc();
       final double x = 123456.789;
       double prod = 1;
       double xOverPow2 = x / 2;
       while (xOverPow2 > 0) {
           prod *= FastMath.cos(xOverPow2);
           xOverPow2 /= 2;
       }
       Assert.assertEquals(prod, s.value(x), 1e-13);
   }

   @Test
   public void testDerivativeZero() {
       final DerivativeStructure s0 = new Sinc(true).value(new DerivativeStructure(1, 1, 0, 0.0));
       Assert.assertEquals(0, s0.getPartialDerivative(1), 0);
   }

   @Test
   public void testDerivatives1Dot2Unnormalized() {
       DerivativeStructure s = new Sinc(false).value(new DerivativeStructure(1, 5, 0, 1.2));
       Assert.assertEquals( 0.77669923830602195806, s.getPartialDerivative(0), 1.0e-16);
       Assert.assertEquals(-0.34528456985779031701, s.getPartialDerivative(1), 1.0e-16);
       Assert.assertEquals(-0.2012249552097047631,  s.getPartialDerivative(2), 1.0e-16);
       Assert.assertEquals( 0.2010975926270339262,  s.getPartialDerivative(3), 4.0e-16);
       Assert.assertEquals( 0.106373929549242204,   s.getPartialDerivative(4), 1.0e-15);
       Assert.assertEquals(-0.1412599110579478695,  s.getPartialDerivative(5), 3.0e-15);
   }

   @Test
   public void testDerivatives1Dot2Normalized() {
       DerivativeStructure s = new Sinc(true).value(new DerivativeStructure(1, 5, 0, 1.2));
       Assert.assertEquals(-0.15591488063143983888, s.getPartialDerivative(0), 6.0e-17);
       Assert.assertEquals(-0.54425176145292298767, s.getPartialDerivative(1), 2.0e-16);
       Assert.assertEquals(2.4459044611635856107,   s.getPartialDerivative(2), 9.0e-16);
       Assert.assertEquals(0.5391369206235909586,   s.getPartialDerivative(3), 7.0e-16);
       Assert.assertEquals(-16.984649869728849865,  s.getPartialDerivative(4), 8.0e-15);
       Assert.assertEquals(5.0980327462666316586,   s.getPartialDerivative(5), 9.0e-15);
   }

   @Test
   public void testDerivativeShortcut() {
       final Sinc sinc = new Sinc();
       final UnivariateFunction f = new UnivariateFunction() {
               public double value(double x) {
                   Dfp dfpX = new DfpField(25).newDfp(x);
                   return DfpMath.cos(dfpX).subtract(DfpMath.sin(dfpX).divide(dfpX)).divide(dfpX).toDouble();
               }
           };

       for (double x = 1e-30; x < 1e10; x *= 2) {
           final double fX = f.value(x);
           final DerivativeStructure sX = sinc.value(new DerivativeStructure(1, 1, 0, x));
           Assert.assertEquals("x=" + x, fX, sX.getPartialDerivative(1), 3.0e-13);
       }
   }
}

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