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Diffstat (limited to 'src/main/java/org/apache/commons/math3/ode/nonstiff/HighamHall54StepInterpolator.java')
| -rw-r--r-- | src/main/java/org/apache/commons/math3/ode/nonstiff/HighamHall54StepInterpolator.java | 122 |
1 files changed, 122 insertions, 0 deletions
diff --git a/src/main/java/org/apache/commons/math3/ode/nonstiff/HighamHall54StepInterpolator.java b/src/main/java/org/apache/commons/math3/ode/nonstiff/HighamHall54StepInterpolator.java new file mode 100644 index 0000000..682ec7c --- /dev/null +++ b/src/main/java/org/apache/commons/math3/ode/nonstiff/HighamHall54StepInterpolator.java @@ -0,0 +1,122 @@ +/* + * 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.nonstiff; + +import org.apache.commons.math3.ode.sampling.StepInterpolator; + +/** + * This class represents an interpolator over the last step during an + * ODE integration for the 5(4) Higham and Hall integrator. + * + * @see HighamHall54Integrator + * + * @since 1.2 + */ + +class HighamHall54StepInterpolator + extends RungeKuttaStepInterpolator { + + /** Serializable version identifier */ + private static final long serialVersionUID = 20111120L; + + /** Simple constructor. + * This constructor builds an instance that is not usable yet, the + * {@link + * org.apache.commons.math3.ode.sampling.AbstractStepInterpolator#reinitialize} + * method should be called before using the instance in order to + * initialize the internal arrays. This constructor is used only + * in order to delay the initialization in some cases. The {@link + * EmbeddedRungeKuttaIntegrator} uses the prototyping design pattern + * to create the step interpolators by cloning an uninitialized model + * and later initializing the copy. + */ + // CHECKSTYLE: stop RedundantModifier + // the public modifier here is needed for serialization + public HighamHall54StepInterpolator() { + super(); + } + // CHECKSTYLE: resume RedundantModifier + + /** Copy constructor. + * @param interpolator interpolator to copy from. The copy is a deep + * copy: its arrays are separated from the original arrays of the + * instance + */ + HighamHall54StepInterpolator(final HighamHall54StepInterpolator interpolator) { + super(interpolator); + } + + /** {@inheritDoc} */ + @Override + protected StepInterpolator doCopy() { + return new HighamHall54StepInterpolator(this); + } + + + /** {@inheritDoc} */ + @Override + protected void computeInterpolatedStateAndDerivatives(final double theta, + final double oneMinusThetaH) { + + final double bDot0 = 1 + theta * (-15.0/2.0 + theta * (16.0 - 10.0 * theta)); + final double bDot2 = theta * (459.0/16.0 + theta * (-729.0/8.0 + 135.0/2.0 * theta)); + final double bDot3 = theta * (-44.0 + theta * (152.0 - 120.0 * theta)); + final double bDot4 = theta * (375.0/16.0 + theta * (-625.0/8.0 + 125.0/2.0 * theta)); + final double bDot5 = theta * 5.0/8.0 * (2 * theta - 1); + + if ((previousState != null) && (theta <= 0.5)) { + final double hTheta = h * theta; + final double b0 = hTheta * (1.0 + theta * (-15.0/4.0 + theta * (16.0/3.0 - 5.0/2.0 * theta))); + final double b2 = hTheta * ( theta * (459.0/32.0 + theta * (-243.0/8.0 + theta * 135.0/8.0))); + final double b3 = hTheta * ( theta * (-22.0 + theta * (152.0/3.0 + theta * -30.0))); + final double b4 = hTheta * ( theta * (375.0/32.0 + theta * (-625.0/24.0 + theta * 125.0/8.0))); + final double b5 = hTheta * ( theta * (-5.0/16.0 + theta * 5.0/12.0)); + for (int i = 0; i < interpolatedState.length; ++i) { + final double yDot0 = yDotK[0][i]; + final double yDot2 = yDotK[2][i]; + final double yDot3 = yDotK[3][i]; + final double yDot4 = yDotK[4][i]; + final double yDot5 = yDotK[5][i]; + interpolatedState[i] = + previousState[i] + b0 * yDot0 + b2 * yDot2 + b3 * yDot3 + b4 * yDot4 + b5 * yDot5; + interpolatedDerivatives[i] = + bDot0 * yDot0 + bDot2 * yDot2 + bDot3 * yDot3 + bDot4 * yDot4 + bDot5 * yDot5; + } + } else { + final double theta2 = theta * theta; + final double b0 = h * (-1.0/12.0 + theta * (1.0 + theta * (-15.0/4.0 + theta * (16.0/3.0 + theta * -5.0/2.0)))); + final double b2 = h * (-27.0/32.0 + theta2 * (459.0/32.0 + theta * (-243.0/8.0 + theta * 135.0/8.0))); + final double b3 = h * (4.0/3.0 + theta2 * (-22.0 + theta * (152.0/3.0 + theta * -30.0))); + final double b4 = h * (-125.0/96.0 + theta2 * (375.0/32.0 + theta * (-625.0/24.0 + theta * 125.0/8.0))); + final double b5 = h * (-5.0/48.0 + theta2 * (-5.0/16.0 + theta * 5.0/12.0)); + for (int i = 0; i < interpolatedState.length; ++i) { + final double yDot0 = yDotK[0][i]; + final double yDot2 = yDotK[2][i]; + final double yDot3 = yDotK[3][i]; + final double yDot4 = yDotK[4][i]; + final double yDot5 = yDotK[5][i]; + interpolatedState[i] = + currentState[i] + b0 * yDot0 + b2 * yDot2 + b3 * yDot3 + b4 * yDot4 + b5 * yDot5; + interpolatedDerivatives[i] = + bDot0 * yDot0 + bDot2 * yDot2 + bDot3 * yDot3 + bDot4 * yDot4 + bDot5 * yDot5; + } + } + + } + +} |