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Diffstat (limited to 'src/main/java/org/apache/commons/math3/ode/nonstiff/EulerFieldIntegrator.java')
-rw-r--r-- | src/main/java/org/apache/commons/math3/ode/nonstiff/EulerFieldIntegrator.java | 96 |
1 files changed, 96 insertions, 0 deletions
diff --git a/src/main/java/org/apache/commons/math3/ode/nonstiff/EulerFieldIntegrator.java b/src/main/java/org/apache/commons/math3/ode/nonstiff/EulerFieldIntegrator.java new file mode 100644 index 0000000..38516cf --- /dev/null +++ b/src/main/java/org/apache/commons/math3/ode/nonstiff/EulerFieldIntegrator.java @@ -0,0 +1,96 @@ +/* + * 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.Field; +import org.apache.commons.math3.RealFieldElement; +import org.apache.commons.math3.ode.FieldEquationsMapper; +import org.apache.commons.math3.ode.FieldODEStateAndDerivative; +import org.apache.commons.math3.util.MathArrays; + +/** + * This class implements a simple Euler integrator for Ordinary + * Differential Equations. + * + * <p>The Euler algorithm is the simplest one that can be used to + * integrate ordinary differential equations. It is a simple inversion + * of the forward difference expression : + * <code>f'=(f(t+h)-f(t))/h</code> which leads to + * <code>f(t+h)=f(t)+hf'</code>. The interpolation scheme used for + * dense output is the linear scheme already used for integration.</p> + * + * <p>This algorithm looks cheap because it needs only one function + * evaluation per step. However, as it uses linear estimates, it needs + * very small steps to achieve high accuracy, and small steps lead to + * numerical errors and instabilities.</p> + * + * <p>This algorithm is almost never used and has been included in + * this package only as a comparison reference for more useful + * integrators.</p> + * + * @see MidpointFieldIntegrator + * @see ClassicalRungeKuttaFieldIntegrator + * @see GillFieldIntegrator + * @see ThreeEighthesFieldIntegrator + * @see LutherFieldIntegrator + * @param <T> the type of the field elements + * @since 3.6 + */ + +public class EulerFieldIntegrator<T extends RealFieldElement<T>> extends RungeKuttaFieldIntegrator<T> { + + /** Simple constructor. + * Build an Euler integrator with the given step. + * @param field field to which the time and state vector elements belong + * @param step integration step + */ + public EulerFieldIntegrator(final Field<T> field, final T step) { + super(field, "Euler", step); + } + + /** {@inheritDoc} */ + public T[] getC() { + return MathArrays.buildArray(getField(), 0); + } + + /** {@inheritDoc} */ + public T[][] getA() { + return MathArrays.buildArray(getField(), 0, 0); + } + + /** {@inheritDoc} */ + public T[] getB() { + final T[] b = MathArrays.buildArray(getField(), 1); + b[0] = getField().getOne(); + return b; + } + + /** {@inheritDoc} */ + @Override + protected EulerFieldStepInterpolator<T> + createInterpolator(final boolean forward, T[][] yDotK, + final FieldODEStateAndDerivative<T> globalPreviousState, + final FieldODEStateAndDerivative<T> globalCurrentState, + final FieldEquationsMapper<T> mapper) { + return new EulerFieldStepInterpolator<T>(getField(), forward, yDotK, + globalPreviousState, globalCurrentState, + globalPreviousState, globalCurrentState, + mapper); + } + +} |