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With inspiration from other libraries
/*
* 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.
* When this filter is used, the wrapped {@link EventHandler
* event handler} {@link EventHandler#eventOccurred(double, double[],
* boolean) eventOccurred} method will be called only with
* its {@code increasing} argument set to false.
*/
TRIGGER_ONLY_DECREASING_EVENTS {
/** {@inheritDoc} */
@Override
protected boolean getTriggeredIncreasing() {
return false;
}
/** {@inheritDoc}
*
* states scheduling for computing h(t,y) as an altered version of g(t, y)
*
* - 0 are triggered events for which a zero is produced (here decreasing events)
* - X are ignored events for which zero is masked (here increasing events)
*
*
*
* g(t)
* ___ ___ ___
* / \ / \ / \
* / \ / \ / \
* / g>0 \ / g>0 \ / g>0 \
* / \ / \ / \
* ----- X --------- 0 --------- X --------- 0 --------- X --------- 0 ---
* / \ / \ / \
* / \ g<0 / \ g<0 / \ g<0
* / \ / \ / \ /
* ___/ \___/ \___/ \___/
*
*
* 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 \ /
* \___/ \___/ \___/
*
*
* As shown by the figure above, several expressions are used to compute h,
* depending on the current state:
*
* - h = max(+s,-g,+g)
* - h = +g
* - h = min(-s,-g,+g)
* - h = -g
*
* where s is a tiny positive value: {@link org.apache.commons.math3.util.Precision#SAFE_MIN}.
*
*/
@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.
* When this filter is used, the wrapped {@link EventHandler
* event handler} {@link EventHandler#eventOccurred(double, double[],
* boolean) eventOccurred} method will be called only with
* its {@code increasing} argument set to true.
*/
TRIGGER_ONLY_INCREASING_EVENTS {
/** {@inheritDoc} */
@Override
protected boolean getTriggeredIncreasing() {
return true;
}
/** {@inheritDoc}
*
* states scheduling for computing h(t,y) as an altered version of g(t, y)
*
* - 0 are triggered events for which a zero is produced (here increasing events)
* - X are ignored events for which zero is masked (here decreasing events)
*
*
*
* g(t)
* ___ ___ ___
* / \ / \ / \
* / \ / \ / \
* / g>0 \ / g>0 \ / g>0 \
* / \ / \ / \
* ----- 0 --------- X --------- 0 --------- X --------- 0 --------- X ---
* / \ / \ / \
* / \ g<0 / \ g<0 / \ g<0
* / \ / \ / \ /
* ___/ \___/ \___/ \___/
*
*
* 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 \ / \ /
* \___/ \___/ \___/ \___/
*
*
* As shown by the figure above, several expressions are used to compute h,
* depending on the current state:
*
* - h = max(+s,-g,+g)
* - h = +g
* - h = min(-s,-g,+g)
* - h = -g
*
* where s is a tiny positive value: {@link org.apache.commons.math3.util.Precision#SAFE_MIN}.
*
*/
@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);
}