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Diffstat (limited to 'src/main/java/org/apache/commons/math3/ode/nonstiff/MidpointFieldIntegrator.java')
-rw-r--r-- | src/main/java/org/apache/commons/math3/ode/nonstiff/MidpointFieldIntegrator.java | 96 |
1 files changed, 96 insertions, 0 deletions
diff --git a/src/main/java/org/apache/commons/math3/ode/nonstiff/MidpointFieldIntegrator.java b/src/main/java/org/apache/commons/math3/ode/nonstiff/MidpointFieldIntegrator.java new file mode 100644 index 0000000..e0dd8cf --- /dev/null +++ b/src/main/java/org/apache/commons/math3/ode/nonstiff/MidpointFieldIntegrator.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 second order Runge-Kutta integrator for + * Ordinary Differential Equations. + * + * <p>This method is an explicit Runge-Kutta method, its Butcher-array + * is the following one : + * <pre> + * 0 | 0 0 + * 1/2 | 1/2 0 + * |---------- + * | 0 1 + * </pre> + * </p> + * + * @see EulerFieldIntegrator + * @see ClassicalRungeKuttaFieldIntegrator + * @see GillFieldIntegrator + * @see ThreeEighthesFieldIntegrator + * @see LutherFieldIntegrator + * + * @param <T> the type of the field elements + * @since 3.6 + */ + +public class MidpointFieldIntegrator<T extends RealFieldElement<T>> extends RungeKuttaFieldIntegrator<T> { + + /** Simple constructor. + * Build a midpoint integrator with the given step. + * @param field field to which the time and state vector elements belong + * @param step integration step + */ + public MidpointFieldIntegrator(final Field<T> field, final T step) { + super(field, "midpoint", step); + } + + /** {@inheritDoc} */ + public T[] getC() { + final T[] c = MathArrays.buildArray(getField(), 1); + c[0] = getField().getOne().multiply(0.5); + return c; + } + + /** {@inheritDoc} */ + public T[][] getA() { + final T[][] a = MathArrays.buildArray(getField(), 1, 1); + a[0][0] = fraction(1, 2); + return a; + } + + /** {@inheritDoc} */ + public T[] getB() { + final T[] b = MathArrays.buildArray(getField(), 2); + b[0] = getField().getZero(); + b[1] = getField().getOne(); + return b; + } + + /** {@inheritDoc} */ + @Override + protected MidpointFieldStepInterpolator<T> + createInterpolator(final boolean forward, T[][] yDotK, + final FieldODEStateAndDerivative<T> globalPreviousState, + final FieldODEStateAndDerivative<T> globalCurrentState, + final FieldEquationsMapper<T> mapper) { + return new MidpointFieldStepInterpolator<T>(getField(), forward, yDotK, + globalPreviousState, globalCurrentState, + globalPreviousState, globalCurrentState, + mapper); + } + +} |