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# Commons Math example source code file (GillIntegrator.java)

This example Commons Math source code file (GillIntegrator.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

## Java - Commons Math tags/keywords

gill, gillintegrator, gillintegrator, gillstepinterpolator, rungekuttaintegrator, static_a, static_a, static_b, static_b, static_c, static_c

## The Commons Math GillIntegrator.java source code

```/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements.  See the NOTICE file distributed with
* 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
*
*
* Unless required by applicable law or agreed to in writing, software
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
*/

package org.apache.commons.math.ode.nonstiff;

/**
* This class implements the Gill fourth 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       0      0
*   1/2 |   1/2       0       0      0
*   1/2 | (q-1)/2  (2-q)/2    0      0
*    1  |    0       -q/2  (2+q)/2   0
*       |-------------------------------
*       |   1/6    (2-q)/6 (2+q)/6  1/6
* </pre>
* where q = sqrt(2)</p>
*
* @see EulerIntegrator
* @see ClassicalRungeKuttaIntegrator
* @see MidpointIntegrator
* @see ThreeEighthesIntegrator
* @version \$Revision: 810196 \$ \$Date: 2009-09-01 15:47:46 -0400 (Tue, 01 Sep 2009) \$
* @since 1.2
*/

public class GillIntegrator extends RungeKuttaIntegrator {

/** Time steps Butcher array. */
private static final double[] STATIC_C = {
1.0 / 2.0, 1.0 / 2.0, 1.0
};

/** Internal weights Butcher array. */
private static final double[][] STATIC_A = {
{ 1.0 / 2.0 },
{ (Math.sqrt(2.0) - 1.0) / 2.0, (2.0 - Math.sqrt(2.0)) / 2.0 },
{ 0.0, -Math.sqrt(2.0) / 2.0, (2.0 + Math.sqrt(2.0)) / 2.0 }
};

/** Propagation weights Butcher array. */
private static final double[] STATIC_B = {
1.0 / 6.0, (2.0 - Math.sqrt(2.0)) / 6.0, (2.0 + Math.sqrt(2.0)) / 6.0, 1.0 / 6.0
};

/** Simple constructor.
* Build a fourth-order Gill integrator with the given step.
* @param step integration step
*/
public GillIntegrator(final double step) {
super("Gill", STATIC_C, STATIC_A, STATIC_B, new GillStepInterpolator(), step);
}

}
```

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