/*
 * 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.math.ode.nonstiff;

import org.apache.commons.math.linear.Array2DRowRealMatrix;
import org.apache.commons.math.ode.DerivativeException;
import org.apache.commons.math.ode.FirstOrderDifferentialEquations;
import org.apache.commons.math.ode.IntegratorException;
import org.apache.commons.math.ode.MultistepIntegrator;

/**
 * Base class for {@link AdamsBashforthIntegrator Adams-Bashforth} and
 * {@link AdamsMoultonIntegrator Adams-Moulton} integrators.
 * 
 * @version $Revision$ $Date$
 * @since 2.0
 */
public abstract class AdamsIntegrator extends MultistepIntegrator {

	/** Transformer. */
	private final AdamsNordsieckTransformer transformer;

	/**
	 * Build an Adams integrator with the given order and step control
	 * prameters.
	 * 
	 * @param name
	 *            name of the method
	 * @param nSteps
	 *            number of steps of the method excluding the one being computed
	 * @param order
	 *            order of the method
	 * @param minStep
	 *            minimal step (must be positive even for backward integration),
	 *            the last step can be smaller than this
	 * @param maxStep
	 *            maximal step (must be positive even for backward integration)
	 * @param scalAbsoluteTolerance
	 *            allowed absolute error
	 * @param scalRelativeTolerance
	 *            allowed relative error
	 * @exception IllegalArgumentException
	 *                if order is 1 or less
	 */
	public AdamsIntegrator(final String name, final int nSteps, final int order, final double minStep,
			final double maxStep, final double scalAbsoluteTolerance, final double scalRelativeTolerance)
			throws IllegalArgumentException {
		super(name, nSteps, order, minStep, maxStep, scalAbsoluteTolerance, scalRelativeTolerance);
		transformer = AdamsNordsieckTransformer.getInstance(nSteps);
	}

	/**
	 * Build an Adams integrator with the given order and step control
	 * parameters.
	 * 
	 * @param name
	 *            name of the method
	 * @param nSteps
	 *            number of steps of the method excluding the one being computed
	 * @param order
	 *            order of the method
	 * @param minStep
	 *            minimal step (must be positive even for backward integration),
	 *            the last step can be smaller than this
	 * @param maxStep
	 *            maximal step (must be positive even for backward integration)
	 * @param vecAbsoluteTolerance
	 *            allowed absolute error
	 * @param vecRelativeTolerance
	 *            allowed relative error
	 * @exception IllegalArgumentException
	 *                if order is 1 or less
	 */
	public AdamsIntegrator(final String name, final int nSteps, final int order, final double minStep,
			final double maxStep, final double[] vecAbsoluteTolerance, final double[] vecRelativeTolerance)
			throws IllegalArgumentException {
		super(name, nSteps, order, minStep, maxStep, vecAbsoluteTolerance, vecRelativeTolerance);
		transformer = AdamsNordsieckTransformer.getInstance(nSteps);
	}

	/** {@inheritDoc} */
	@Override
	public abstract double integrate(final FirstOrderDifferentialEquations equations, final double t0,
			final double[] y0, final double t, final double[] y) throws DerivativeException, IntegratorException;

	/** {@inheritDoc} */
	@Override
	protected Array2DRowRealMatrix initializeHighOrderDerivatives(final double[] first, final double[][] multistep) {
		return transformer.initializeHighOrderDerivatives(first, multistep);
	}

	/**
	 * Update the high order scaled derivatives for Adams integrators (phase 1).
	 * <p>
	 * The complete update of high order derivatives has a form similar to:
	 * 
	 * <pre>
	 * r<sub>n+1</sub> = (s<sub>1</sub>(n) - s<sub>1</sub>(n+1)) P<sup>-1</sup> u + P<sup>-1</sup> A P r<sub>n</sub>
	 * </pre>
	 * 
	 * this method computes the P<sup>-1</sup> A P r<sub>n</sub> part.
	 * </p>
	 * 
	 * @param highOrder
	 *            high order scaled derivatives (h<sup>2</sup>/2 y'', ...
	 *            h<sup>k</sup>/k! y(k))
	 * @return updated high order derivatives
	 * @see #updateHighOrderDerivativesPhase2(double[], double[],
	 *      Array2DRowRealMatrix)
	 */
	public Array2DRowRealMatrix updateHighOrderDerivativesPhase1(final Array2DRowRealMatrix highOrder) {
		return transformer.updateHighOrderDerivativesPhase1(highOrder);
	}

	/**
	 * Update the high order scaled derivatives Adams integrators (phase 2).
	 * <p>
	 * The complete update of high order derivatives has a form similar to:
	 * 
	 * <pre>
	 * r<sub>n+1</sub> = (s<sub>1</sub>(n) - s<sub>1</sub>(n+1)) P<sup>-1</sup> u + P<sup>-1</sup> A P r<sub>n</sub>
	 * </pre>
	 * 
	 * this method computes the (s<sub>1</sub>(n) - s<sub>1</sub>(n+1))
	 * P<sup>-1</sup> u part.
	 * </p>
	 * <p>
	 * Phase 1 of the update must already have been performed.
	 * </p>
	 * 
	 * @param start
	 *            first order scaled derivatives at step start
	 * @param end
	 *            first order scaled derivatives at step end
	 * @param highOrder
	 *            high order scaled derivatives, will be modified
	 *            (h<sup>2</sup>/2 y'', ... h<sup>k</sup>/k! y(k))
	 * @see #updateHighOrderDerivativesPhase1(Array2DRowRealMatrix)
	 */
	public void updateHighOrderDerivativesPhase2(final double[] start, final double[] end,
			final Array2DRowRealMatrix highOrder) {
		transformer.updateHighOrderDerivativesPhase2(start, end, highOrder);
	}

}
