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Java example source code file (FilterType.java)

This example Java source code file (FilterType.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

filtertype, mathinternalerror, max, min, minus, override, plus, transformer, trigger_only_decreasing_events, trigger_only_increasing_events, uninitialized

The FilterType.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.ode.events;

import org.apache.commons.math3.exception.MathInternalError;

/** Enumerate for {@link EventFilter filtering events}.
 *
 * @since 3.2
 */

public enum FilterType {

    /** Constant for triggering only decreasing events.
     * <p>When this filter is used, the wrapped {@link EventHandler
     * event handler} {@link EventHandler#eventOccurred(double, double[],
     * boolean) eventOccurred} method will be called <em>only with
     * its {@code increasing} argument set to false.</p>
     */
    TRIGGER_ONLY_DECREASING_EVENTS {

        /**  {@inheritDoc} */
        @Override
        protected boolean getTriggeredIncreasing() {
            return false;
        }

        /** {@inheritDoc}
         * <p>
         * states scheduling for computing h(t,y) as an altered version of g(t, y)
         * <ul>
         * <li>0 are triggered events for which a zero is produced (here decreasing events)
         * <li>X are ignored events for which zero is masked (here increasing events)
         * </ul>
         * </p>
         * <pre>
         *  g(t)
         *             ___                     ___                     ___
         *            /   \                   /   \                   /   \
         *           /     \                 /     \                 /     \
         *          /  g>0  \               /  g>0  \               /  g>0  \
         *         /         \             /         \             /         \
         *  ----- X --------- 0 --------- X --------- 0 --------- X --------- 0 ---
         *       /             \         /             \         /             \
         *      /               \ g<0   /               \  g<0  /               \ g<0
         *     /                 \     /                 \     /                 \     /
         * ___/                   \___/                   \___/                   \___/
         * </pre>
         * <pre>
         *  h(t,y)) as an alteration of g(t,y)
         *             ___                                 ___         ___
         *    \       /   \                               /   \       /   \
         *     \     /     \ h=+g                        /     \     /     \
         *      \   /       \      h=min(-s,-g,+g)      /       \   /       \
         *       \_/         \                         /         \_/         \
         *  ------ ---------- 0 ----------_---------- 0 --------------------- 0 ---
         *                     \         / \         /                         \
         *   h=max(+s,-g,+g)    \       /   \       /       h=max(+s,-g,+g)     \
         *                       \     /     \     / h=-g                        \     /
         *                        \___/       \___/                               \___/
         * </pre>
         * <p>
         * As shown by the figure above, several expressions are used to compute h,
         * depending on the current state:
         * <ul>
         *   <li>h = max(+s,-g,+g)
         *   <li>h = +g
         *   <li>h = min(-s,-g,+g)
         *   <li>h = -g
         * </ul>
         * where s is a tiny positive value: {@link org.apache.commons.math3.util.Precision#SAFE_MIN}.
         * </p>
         */
        @Override
        protected  Transformer selectTransformer(final Transformer previous,
                                                 final double g, final boolean forward) {
            if (forward) {
                switch (previous) {
                    case UNINITIALIZED :
                        // we are initializing the first point
                        if (g > 0) {
                            // initialize as if previous root (i.e. backward one) was an ignored increasing event
                            return Transformer.MAX;
                        } else if (g < 0) {
                            // initialize as if previous root (i.e. backward one) was a triggered decreasing event
                            return Transformer.PLUS;
                        } else {
                            // we are exactly at a root, we don't know if it is an increasing
                            // or a decreasing event, we remain in uninitialized state
                            return Transformer.UNINITIALIZED;
                        }
                    case PLUS  :
                        if (g >= 0) {
                            // we have crossed the zero line on an ignored increasing event,
                            // we must change the transformer
                            return Transformer.MIN;
                        } else {
                            // we are still in the same status
                            return previous;
                        }
                    case MINUS :
                        if (g >= 0) {
                            // we have crossed the zero line on an ignored increasing event,
                            // we must change the transformer
                            return Transformer.MAX;
                        } else {
                            // we are still in the same status
                            return previous;
                        }
                    case MIN   :
                        if (g <= 0) {
                            // we have crossed the zero line on a triggered decreasing event,
                            // we must change the transformer
                            return Transformer.MINUS;
                        } else {
                            // we are still in the same status
                            return previous;
                        }
                    case MAX   :
                        if (g <= 0) {
                            // we have crossed the zero line on a triggered decreasing event,
                            // we must change the transformer
                            return Transformer.PLUS;
                        } else {
                            // we are still in the same status
                            return previous;
                        }
                    default    :
                        // this should never happen
                        throw new MathInternalError();
                }
            } else {
                switch (previous) {
                    case UNINITIALIZED :
                        // we are initializing the first point
                        if (g > 0) {
                            // initialize as if previous root (i.e. forward one) was a triggered decreasing event
                            return Transformer.MINUS;
                        } else if (g < 0) {
                            // initialize as if previous root (i.e. forward one) was an ignored increasing event
                            return Transformer.MIN;
                        } else {
                            // we are exactly at a root, we don't know if it is an increasing
                            // or a decreasing event, we remain in uninitialized state
                            return Transformer.UNINITIALIZED;
                        }
                    case PLUS  :
                        if (g <= 0) {
                            // we have crossed the zero line on an ignored increasing event,
                            // we must change the transformer
                            return Transformer.MAX;
                        } else {
                            // we are still in the same status
                            return previous;
                        }
                    case MINUS :
                        if (g <= 0) {
                            // we have crossed the zero line on an ignored increasing event,
                            // we must change the transformer
                            return Transformer.MIN;
                        } else {
                            // we are still in the same status
                            return previous;
                        }
                    case MIN   :
                        if (g >= 0) {
                            // we have crossed the zero line on a triggered decreasing event,
                            // we must change the transformer
                            return Transformer.PLUS;
                        } else {
                            // we are still in the same status
                            return previous;
                        }
                    case MAX   :
                        if (g >= 0) {
                            // we have crossed the zero line on a triggered decreasing event,
                            // we must change the transformer
                            return Transformer.MINUS;
                        } else {
                            // we are still in the same status
                            return previous;
                        }
                    default    :
                        // this should never happen
                        throw new MathInternalError();
                }
            }
        }

    },

    /** Constant for triggering only increasing events.
     * <p>When this filter is used, the wrapped {@link EventHandler
     * event handler} {@link EventHandler#eventOccurred(double, double[],
     * boolean) eventOccurred} method will be called <em>only with
     * its {@code increasing} argument set to true.</p>
     */
    TRIGGER_ONLY_INCREASING_EVENTS {

        /**  {@inheritDoc} */
        @Override
        protected boolean getTriggeredIncreasing() {
            return true;
        }

        /** {@inheritDoc}
         * <p>
         * states scheduling for computing h(t,y) as an altered version of g(t, y)
         * <ul>
         * <li>0 are triggered events for which a zero is produced (here increasing events)
         * <li>X are ignored events for which zero is masked (here decreasing events)
         * </ul>
         * </p>
         * <pre>
         *  g(t)
         *             ___                     ___                     ___
         *            /   \                   /   \                   /   \
         *           /     \                 /     \                 /     \
         *          /  g>0  \               /  g>0  \               /  g>0  \
         *         /         \             /         \             /         \
         *  ----- 0 --------- X --------- 0 --------- X --------- 0 --------- X ---
         *       /             \         /             \         /             \
         *      /               \ g<0   /               \  g<0  /               \ g<0
         *     /                 \     /                 \     /                 \     /
         * ___/                   \___/                   \___/                   \___/
         * </pre>
         * <pre>
         *  h(t,y)) as an alteration of g(t,y)
         *                                     ___         ___
         *    \                               /   \       /   \
         *     \ h=-g                        /     \     /     \ h=-g
         *      \      h=min(-s,-g,+g)      /       \   /       \      h=min(-s,-g,+g)
         *       \                         /         \_/         \
         *  ------0 ----------_---------- 0 --------------------- 0 --------- _ ---
         *         \         / \         /                         \         / \
         *          \       /   \       /       h=max(+s,-g,+g)     \       /   \
         *           \     /     \     / h=+g                        \     /     \     /
         *            \___/       \___/                               \___/       \___/
         * </pre>
         * <p>
         * As shown by the figure above, several expressions are used to compute h,
         * depending on the current state:
         * <ul>
         *   <li>h = max(+s,-g,+g)
         *   <li>h = +g
         *   <li>h = min(-s,-g,+g)
         *   <li>h = -g
         * </ul>
         * where s is a tiny positive value: {@link org.apache.commons.math3.util.Precision#SAFE_MIN}.
         * </p>
         */
        @Override
        protected  Transformer selectTransformer(final Transformer previous,
                                                 final double g, final boolean forward) {
            if (forward) {
                switch (previous) {
                    case UNINITIALIZED :
                        // we are initializing the first point
                        if (g > 0) {
                            // initialize as if previous root (i.e. backward one) was a triggered increasing event
                            return Transformer.PLUS;
                        } else if (g < 0) {
                            // initialize as if previous root (i.e. backward one) was an ignored decreasing event
                            return Transformer.MIN;
                        } else {
                            // we are exactly at a root, we don't know if it is an increasing
                            // or a decreasing event, we remain in uninitialized state
                            return Transformer.UNINITIALIZED;
                        }
                    case PLUS  :
                        if (g <= 0) {
                            // we have crossed the zero line on an ignored decreasing event,
                            // we must change the transformer
                            return Transformer.MAX;
                        } else {
                            // we are still in the same status
                            return previous;
                        }
                    case MINUS :
                        if (g <= 0) {
                            // we have crossed the zero line on an ignored decreasing event,
                            // we must change the transformer
                            return Transformer.MIN;
                        } else {
                            // we are still in the same status
                            return previous;
                        }
                    case MIN   :
                        if (g >= 0) {
                            // we have crossed the zero line on a triggered increasing event,
                            // we must change the transformer
                            return Transformer.PLUS;
                        } else {
                            // we are still in the same status
                            return previous;
                        }
                    case MAX   :
                        if (g >= 0) {
                            // we have crossed the zero line on a triggered increasing event,
                            // we must change the transformer
                            return Transformer.MINUS;
                        } else {
                            // we are still in the same status
                            return previous;
                        }
                    default    :
                        // this should never happen
                        throw new MathInternalError();
                }
            } else {
                switch (previous) {
                    case UNINITIALIZED :
                        // we are initializing the first point
                        if (g > 0) {
                            // initialize as if previous root (i.e. forward one) was an ignored decreasing event
                            return Transformer.MAX;
                        } else if (g < 0) {
                            // initialize as if previous root (i.e. forward one) was a triggered increasing event
                            return Transformer.MINUS;
                        } else {
                            // we are exactly at a root, we don't know if it is an increasing
                            // or a decreasing event, we remain in uninitialized state
                            return Transformer.UNINITIALIZED;
                        }
                    case PLUS  :
                        if (g >= 0) {
                            // we have crossed the zero line on an ignored decreasing event,
                            // we must change the transformer
                            return Transformer.MIN;
                        } else {
                            // we are still in the same status
                            return previous;
                        }
                    case MINUS :
                        if (g >= 0) {
                            // we have crossed the zero line on an ignored decreasing event,
                            // we must change the transformer
                            return Transformer.MAX;
                        } else {
                            // we are still in the same status
                            return previous;
                        }
                    case MIN   :
                        if (g <= 0) {
                            // we have crossed the zero line on a triggered increasing event,
                            // we must change the transformer
                            return Transformer.MINUS;
                        } else {
                            // we are still in the same status
                            return previous;
                        }
                    case MAX   :
                        if (g <= 0) {
                            // we have crossed the zero line on a triggered increasing event,
                            // we must change the transformer
                            return Transformer.PLUS;
                        } else {
                            // we are still in the same status
                            return previous;
                        }
                    default    :
                        // this should never happen
                        throw new MathInternalError();
                }
            }
        }

    };

    /** Get the increasing status of triggered events.
     * @return true if triggered events are increasing events
     */
    protected abstract boolean getTriggeredIncreasing();

    /** Get next function transformer in the specified direction.
     * @param previous transformer active on the previous point with respect
     * to integration direction (may be null if no previous point is known)
     * @param g current value of the g function
     * @param forward true if integration goes forward
     * @return next transformer transformer
     */
    protected abstract Transformer selectTransformer(Transformer previous,
                                                     double g, boolean forward);

}

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