Java example source code file (FastCosineTransformerTest.java)

This example Java source code file (FastCosineTransformerTest.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

assert, dctnormalization, expecting, fastcosinetransformer, fastcosinetransformertest, illegalargumentexception, mathillegalstateexception, override, parameters, realtransformerabstracttest, sinc, test, univariatefunction, util

The FastCosineTransformerTest.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.transform;

import java.util.Arrays;
import java.util.Collection;

import org.apache.commons.math3.analysis.UnivariateFunction;
import org.apache.commons.math3.analysis.function.Sin;
import org.apache.commons.math3.analysis.function.Sinc;
import org.apache.commons.math3.exception.MathIllegalStateException;
import org.apache.commons.math3.util.FastMath;
import org.junit.Assert;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.Parameterized;
import org.junit.runners.Parameterized.Parameters;

/**
 * Test case for fast cosine transformer.
 * <p>
 * FCT algorithm is exact, the small tolerance number is used only to account
 * for round-off errors.
 *
 */
@RunWith(value = Parameterized.class)
public final class FastCosineTransformerTest
    extends RealTransformerAbstractTest {

    private DctNormalization normalization;

    private final int[] invalidDataSize;

    private final double[] relativeTolerance;

    private final int[] validDataSize;

    public FastCosineTransformerTest(final DctNormalization normalization) {
        this.normalization = normalization;
        this.validDataSize = new int[] {
            2, 3, 5, 9, 17, 33, 65, 129
        };
        this.invalidDataSize = new int[] {
            128
        };
        this.relativeTolerance = new double[] {
            1E-15, 1E-15, 1E-14, 1E-13, 1E-13, 1E-12, 1E-11, 1E-10
        };
    }

    /**
     * Returns an array containing {@code true, false} in order to check both
     * standard and orthogonal DCTs.
     *
     * @return an array of parameters for this parameterized test
     */
    @Parameters
    public static Collection<Object[]> data() {
        final DctNormalization[] normalization = DctNormalization.values();
        final Object[][] data = new DctNormalization[normalization.length][1];
        for (int i = 0; i < normalization.length; i++){
            data[i][0] = normalization[i];
        }
        return Arrays.asList(data);
    }

    @Override
    RealTransformer createRealTransformer() {
        return new FastCosineTransformer(normalization);
    }

    @Override
    int getInvalidDataSize(final int i) {
        return invalidDataSize[i];
    }

    @Override
    int getNumberOfInvalidDataSizes() {
        return invalidDataSize.length;
    }

    @Override
    int getNumberOfValidDataSizes() {
        return validDataSize.length;
    }

    @Override
    double getRelativeTolerance(final int i) {
        return relativeTolerance[i];
    }

    @Override
    int getValidDataSize(final int i) {
        return validDataSize[i];
    }

    @Override
    UnivariateFunction getValidFunction() {
        return new Sinc();
    }

    @Override
    double getValidLowerBound() {
        return 0.0;
    }

    @Override
    double getValidUpperBound() {
        return FastMath.PI;
    }

    @Override
    double[] transform(final double[] x, final TransformType type) {
        final int n = x.length;
        final double[] y = new double[n];
        final double[] cos = new double[2 * (n - 1)];
        for (int i = 0; i < cos.length; i++) {
            cos[i] = FastMath.cos(FastMath.PI * i / (n - 1.0));
        }
        int sgn = 1;
        for (int j = 0; j < n; j++) {
            double yj = 0.5 * (x[0] + sgn * x[n - 1]);
            for (int i = 1; i < n - 1; i++) {
                yj += x[i] * cos[(i * j) % cos.length];
            }
            y[j] = yj;
            sgn *= -1;
        }
        final double s;
        if (type == TransformType.FORWARD) {
            if (normalization == DctNormalization.STANDARD_DCT_I) {
                s = 1.0;
            } else if (normalization == DctNormalization.ORTHOGONAL_DCT_I) {
                s = FastMath.sqrt(2.0 / (n - 1.0));
            } else {
                throw new MathIllegalStateException();
            }
        } else if (type == TransformType.INVERSE) {
            if (normalization == DctNormalization.STANDARD_DCT_I) {
                s = 2.0 / (n - 1.0);
            } else if (normalization == DctNormalization.ORTHOGONAL_DCT_I) {
                s = FastMath.sqrt(2.0 / (n - 1.0));
            } else {
                throw new MathIllegalStateException();
            }
        } else {
            /*
             * Should never occur. This clause is a safeguard in case other
             * types are used to TransformType (which should not be done).
             */
            throw new MathIllegalStateException();
        }
        TransformUtils.scaleArray(y, s);
        return y;
    }

    /*
     * Additional tests.
     */

    /** Test of transformer for the ad hoc data. */
    @Test
    public void testAdHocData() {
        FastCosineTransformer transformer;
        transformer = new FastCosineTransformer(DctNormalization.STANDARD_DCT_I);
        double result[], tolerance = 1E-12;

        double x[] = {
            0.0, 1.0, 4.0, 9.0, 16.0, 25.0, 36.0, 49.0, 64.0
        };
        double y[] =
            {
                172.0, -105.096569476353, 27.3137084989848, -12.9593152353742,
                8.0, -5.78585076868676, 4.68629150101524, -4.15826451958632,
                4.0
            };

        result = transformer.transform(x, TransformType.FORWARD);
        for (int i = 0; i < result.length; i++) {
            Assert.assertEquals(y[i], result[i], tolerance);
        }

        result = transformer.transform(y, TransformType.INVERSE);
        for (int i = 0; i < result.length; i++) {
            Assert.assertEquals(x[i], result[i], tolerance);
        }

        TransformUtils.scaleArray(x, FastMath.sqrt(0.5 * (x.length - 1)));

        transformer = new FastCosineTransformer(DctNormalization.ORTHOGONAL_DCT_I);
        result = transformer.transform(y, TransformType.FORWARD);
        for (int i = 0; i < result.length; i++) {
            Assert.assertEquals(x[i], result[i], tolerance);
        }

        result = transformer.transform(x, TransformType.INVERSE);
        for (int i = 0; i < result.length; i++) {
            Assert.assertEquals(y[i], result[i], tolerance);
        }
    }

    /** Test of parameters for the transformer. */
    @Test
    public void testParameters()
        throws Exception {
        UnivariateFunction f = new Sin();
        FastCosineTransformer transformer;
        transformer = new FastCosineTransformer(DctNormalization.STANDARD_DCT_I);

        try {
            // bad interval
            transformer.transform(f, 1, -1, 65, TransformType.FORWARD);
            Assert.fail("Expecting IllegalArgumentException - bad interval");
        } catch (IllegalArgumentException ex) {
            // expected
        }
        try {
            // bad samples number
            transformer.transform(f, -1, 1, 1, TransformType.FORWARD);
            Assert
                .fail("Expecting IllegalArgumentException - bad samples number");
        } catch (IllegalArgumentException ex) {
            // expected
        }
        try {
            // bad samples number
            transformer.transform(f, -1, 1, 64, TransformType.FORWARD);
            Assert
                .fail("Expecting IllegalArgumentException - bad samples number");
        } catch (IllegalArgumentException ex) {
            // expected
        }
    }

    /** Test of transformer for the sine function. */
    @Test
    public void testSinFunction() {
        UnivariateFunction f = new Sin();
        FastCosineTransformer transformer;
        transformer = new FastCosineTransformer(DctNormalization.STANDARD_DCT_I);
        double min, max, result[], tolerance = 1E-12;
        int N = 9;

        double expected[] =
            {
                0.0, 3.26197262739567, 0.0, -2.17958042710327, 0.0,
                -0.648846697642915, 0.0, -0.433545502649478, 0.0
            };
        min = 0.0;
        max = 2.0 * FastMath.PI * N / (N - 1);
        result = transformer.transform(f, min, max, N, TransformType.FORWARD);
        for (int i = 0; i < N; i++) {
            Assert.assertEquals(expected[i], result[i], tolerance);
        }

        min = -FastMath.PI;
        max = FastMath.PI * (N + 1) / (N - 1);
        result = transformer.transform(f, min, max, N, TransformType.FORWARD);
        for (int i = 0; i < N; i++) {
            Assert.assertEquals(-expected[i], result[i], tolerance);
        }
    }
}