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

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;

import org.apache.commons.math.ode.DerivativeException;
import org.apache.commons.math.ode.FirstOrderIntegrator;
import org.apache.commons.math.ode.IntegratorException;
import org.apache.commons.math.ode.TestProblem1;
import org.apache.commons.math.ode.TestProblem5;
import org.apache.commons.math.ode.TestProblem6;
import org.apache.commons.math.ode.TestProblemHandler;
import org.junit.Test;

public class AdamsMoultonIntegratorTest {

	@Test(expected = IntegratorException.class)
	public void dimensionCheck() throws DerivativeException, IntegratorException {
		TestProblem1 pb = new TestProblem1();
		FirstOrderIntegrator integ = new AdamsMoultonIntegrator(2, 0.0, 1.0, 1.0e-10, 1.0e-10);
		integ.integrate(pb, 0.0, new double[pb.getDimension() + 10], 1.0, new double[pb.getDimension() + 10]);
	}

	@Test(expected = IntegratorException.class)
	public void testMinStep() throws DerivativeException, IntegratorException {

		TestProblem1 pb = new TestProblem1();
		double minStep = 0.1 * (pb.getFinalTime() - pb.getInitialTime());
		double maxStep = pb.getFinalTime() - pb.getInitialTime();
		double[] vecAbsoluteTolerance = { 1.0e-15, 1.0e-16 };
		double[] vecRelativeTolerance = { 1.0e-15, 1.0e-16 };

		FirstOrderIntegrator integ = new AdamsMoultonIntegrator(4, minStep, maxStep, vecAbsoluteTolerance,
				vecRelativeTolerance);
		TestProblemHandler handler = new TestProblemHandler(pb, integ);
		integ.addStepHandler(handler);
		integ.integrate(pb, pb.getInitialTime(), pb.getInitialState(), pb.getFinalTime(),
				new double[pb.getDimension()]);

	}

	@Test
	public void testIncreasingTolerance() throws DerivativeException, IntegratorException {

		int previousCalls = Integer.MAX_VALUE;
		for (int i = -12; i < -2; ++i) {
			TestProblem1 pb = new TestProblem1();
			double minStep = 0;
			double maxStep = pb.getFinalTime() - pb.getInitialTime();
			double scalAbsoluteTolerance = Math.pow(10.0, i);
			double scalRelativeTolerance = 0.01 * scalAbsoluteTolerance;

			FirstOrderIntegrator integ = new AdamsMoultonIntegrator(4, minStep, maxStep, scalAbsoluteTolerance,
					scalRelativeTolerance);
			TestProblemHandler handler = new TestProblemHandler(pb, integ);
			integ.addStepHandler(handler);
			integ.integrate(pb, pb.getInitialTime(), pb.getInitialState(), pb.getFinalTime(),
					new double[pb.getDimension()]);

			// the 0.4 and 3.0 factors are only valid for this test
			// and has been obtained from trial and error
			// there is no general relation between local and global errors
			assertTrue(handler.getMaximalValueError() > (0.4 * scalAbsoluteTolerance));
			assertTrue(handler.getMaximalValueError() < (3.0 * scalAbsoluteTolerance));
			assertEquals(0, handler.getMaximalTimeError(), 1.0e-16);

			int calls = pb.getCalls();
			assertEquals(integ.getEvaluations(), calls);
			assertTrue(calls <= previousCalls);
			previousCalls = calls;

		}

	}

	@Test(expected = DerivativeException.class)
	public void exceedMaxEvaluations() throws DerivativeException, IntegratorException {

		TestProblem1 pb = new TestProblem1();
		double range = pb.getFinalTime() - pb.getInitialTime();

		AdamsMoultonIntegrator integ = new AdamsMoultonIntegrator(2, 0, range, 1.0e-12, 1.0e-12);
		TestProblemHandler handler = new TestProblemHandler(pb, integ);
		integ.addStepHandler(handler);
		integ.setMaxEvaluations(650);
		integ.integrate(pb, pb.getInitialTime(), pb.getInitialState(), pb.getFinalTime(),
				new double[pb.getDimension()]);

	}

	@Test
	public void backward() throws DerivativeException, IntegratorException {

		TestProblem5 pb = new TestProblem5();
		double range = Math.abs(pb.getFinalTime() - pb.getInitialTime());

		FirstOrderIntegrator integ = new AdamsMoultonIntegrator(4, 0, range, 1.0e-12, 1.0e-12);
		TestProblemHandler handler = new TestProblemHandler(pb, integ);
		integ.addStepHandler(handler);
		integ.integrate(pb, pb.getInitialTime(), pb.getInitialState(), pb.getFinalTime(),
				new double[pb.getDimension()]);

		assertTrue(handler.getLastError() < 1.0e-9);
		assertTrue(handler.getMaximalValueError() < 1.0e-9);
		assertEquals(0, handler.getMaximalTimeError(), 1.0e-16);
		assertEquals("Adams-Moulton", integ.getName());
	}

	@Test
	public void polynomial() throws DerivativeException, IntegratorException {
		TestProblem6 pb = new TestProblem6();
		double range = Math.abs(pb.getFinalTime() - pb.getInitialTime());

		for (int nSteps = 1; nSteps < 7; ++nSteps) {
			AdamsMoultonIntegrator integ = new AdamsMoultonIntegrator(nSteps, 1.0e-6 * range, 0.1 * range, 1.0e-9,
					1.0e-9);
			TestProblemHandler handler = new TestProblemHandler(pb, integ);
			integ.addStepHandler(handler);
			integ.integrate(pb, pb.getInitialTime(), pb.getInitialState(), pb.getFinalTime(),
					new double[pb.getDimension()]);
			if (nSteps < 4) {
				assertTrue(integ.getEvaluations() > 150);
			} else {
				assertTrue(integ.getEvaluations() < 90);
			}
		}

	}

}
