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From l..@apache.org
Subject [05/14] [math] Renamed abstract test classes to match build environment filters.
Date Sat, 02 Jan 2016 19:07:05 GMT
http://git-wip-us.apache.org/repos/asf/commons-math/blob/29649959/src/test/java/org/apache/commons/math3/ode/nonstiff/RungeKuttaFieldIntegratorAbstractTest.java
----------------------------------------------------------------------
diff --git a/src/test/java/org/apache/commons/math3/ode/nonstiff/RungeKuttaFieldIntegratorAbstractTest.java b/src/test/java/org/apache/commons/math3/ode/nonstiff/RungeKuttaFieldIntegratorAbstractTest.java
new file mode 100644
index 0000000..518690a
--- /dev/null
+++ b/src/test/java/org/apache/commons/math3/ode/nonstiff/RungeKuttaFieldIntegratorAbstractTest.java
@@ -0,0 +1,662 @@
+/*
+ * 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 java.lang.reflect.Array;
+
+import org.apache.commons.math3.Field;
+import org.apache.commons.math3.RealFieldElement;
+import org.apache.commons.math3.analysis.differentiation.DerivativeStructure;
+import org.apache.commons.math3.exception.DimensionMismatchException;
+import org.apache.commons.math3.exception.MaxCountExceededException;
+import org.apache.commons.math3.exception.NoBracketingException;
+import org.apache.commons.math3.exception.NumberIsTooSmallException;
+import org.apache.commons.math3.ode.FieldExpandableODE;
+import org.apache.commons.math3.ode.FirstOrderFieldDifferentialEquations;
+import org.apache.commons.math3.ode.FieldODEState;
+import org.apache.commons.math3.ode.FieldODEStateAndDerivative;
+import org.apache.commons.math3.ode.TestFieldProblem1;
+import org.apache.commons.math3.ode.TestFieldProblem2;
+import org.apache.commons.math3.ode.TestFieldProblem3;
+import org.apache.commons.math3.ode.TestFieldProblem4;
+import org.apache.commons.math3.ode.TestFieldProblem5;
+import org.apache.commons.math3.ode.TestFieldProblem6;
+import org.apache.commons.math3.ode.TestFieldProblemAbstract;
+import org.apache.commons.math3.ode.TestFieldProblemHandler;
+import org.apache.commons.math3.ode.events.Action;
+import org.apache.commons.math3.ode.events.FieldEventHandler;
+import org.apache.commons.math3.ode.sampling.FieldStepHandler;
+import org.apache.commons.math3.ode.sampling.FieldStepInterpolator;
+import org.apache.commons.math3.ode.sampling.StepInterpolatorTestUtils;
+import org.apache.commons.math3.util.FastMath;
+import org.apache.commons.math3.util.MathArrays;
+import org.junit.Assert;
+import org.junit.Test;
+
+public abstract class RungeKuttaFieldIntegratorAbstractTest {
+
+    protected abstract <T extends RealFieldElement<T>> RungeKuttaFieldIntegrator<T>
+        createIntegrator(Field<T> field, T step);
+
+    @Test
+    public abstract void testNonFieldIntegratorConsistency();
+
+    protected <T extends RealFieldElement<T>> void doTestNonFieldIntegratorConsistency(final Field<T> field) {
+        try {
+
+            // get the Butcher arrays from the field integrator
+            RungeKuttaFieldIntegrator<T> fieldIntegrator = createIntegrator(field, field.getZero().add(1));
+            T[][] fieldA = fieldIntegrator.getA();
+            T[]   fieldB = fieldIntegrator.getB();
+            T[]   fieldC = fieldIntegrator.getC();
+
+            String fieldName   = fieldIntegrator.getClass().getName();
+            String regularName = fieldName.replaceAll("Field", "");
+
+            // get the Butcher arrays from the regular integrator
+            @SuppressWarnings("unchecked")
+            Class<RungeKuttaIntegrator> c = (Class<RungeKuttaIntegrator>) Class.forName(regularName);
+            java.lang.reflect.Field jlrFieldA = c.getDeclaredField("STATIC_A");
+            jlrFieldA.setAccessible(true);
+            double[][] regularA = (double[][]) jlrFieldA.get(null);
+            java.lang.reflect.Field jlrFieldB = c.getDeclaredField("STATIC_B");
+            jlrFieldB.setAccessible(true);
+            double[]   regularB = (double[])   jlrFieldB.get(null);
+            java.lang.reflect.Field jlrFieldC = c.getDeclaredField("STATIC_C");
+            jlrFieldC.setAccessible(true);
+            double[]   regularC = (double[])   jlrFieldC.get(null);
+
+            Assert.assertEquals(regularA.length, fieldA.length);
+            for (int i = 0; i < regularA.length; ++i) {
+                checkArray(regularA[i], fieldA[i]);
+            }
+            checkArray(regularB, fieldB);
+            checkArray(regularC, fieldC);
+
+        } catch (ClassNotFoundException cnfe) {
+            Assert.fail(cnfe.getLocalizedMessage());
+        } catch (IllegalAccessException iae) {
+            Assert.fail(iae.getLocalizedMessage());
+        } catch (IllegalArgumentException iae) {
+            Assert.fail(iae.getLocalizedMessage());
+        } catch (SecurityException se) {
+            Assert.fail(se.getLocalizedMessage());
+        } catch (NoSuchFieldException nsfe) {
+            Assert.fail(nsfe.getLocalizedMessage());
+        }
+    }
+
+    private <T extends RealFieldElement<T>> void checkArray(double[] regularArray, T[] fieldArray) {
+        Assert.assertEquals(regularArray.length, fieldArray.length);
+        for (int i = 0; i < regularArray.length; ++i) {
+            if (regularArray[i] == 0) {
+                Assert.assertTrue(0.0 == fieldArray[i].getReal());
+            } else {
+                Assert.assertEquals(regularArray[i], fieldArray[i].getReal(), FastMath.ulp(regularArray[i]));
+            }
+        }
+    }
+
+    @Test
+    public abstract void testMissedEndEvent();
+
+    protected <T extends RealFieldElement<T>> void doTestMissedEndEvent(final Field<T> field,
+                                                                        final double epsilonT, final double epsilonY)
+        throws DimensionMismatchException, NumberIsTooSmallException,
+            MaxCountExceededException, NoBracketingException {
+        final T   t0     = field.getZero().add(1878250320.0000029);
+        final T   tEvent = field.getZero().add(1878250379.9999986);
+        final T[] k      = MathArrays.buildArray(field, 3);
+        k[0] = field.getZero().add(1.0e-4);
+        k[1] = field.getZero().add(1.0e-5);
+        k[2] = field.getZero().add(1.0e-6);
+        FirstOrderFieldDifferentialEquations<T> ode = new FirstOrderFieldDifferentialEquations<T>() {
+
+            public int getDimension() {
+                return k.length;
+            }
+
+            public void init(T t0, T[] y0, T t) {
+            }
+
+            public T[] computeDerivatives(T t, T[] y) {
+                T[] yDot = MathArrays.buildArray(field, k.length);
+                for (int i = 0; i < y.length; ++i) {
+                    yDot[i] = k[i].multiply(y[i]);
+                }
+                return yDot;
+            }
+        };
+
+        RungeKuttaFieldIntegrator<T> integrator = createIntegrator(field, field.getZero().add(60.0));
+
+        T[] y0   = MathArrays.buildArray(field, k.length);
+        for (int i = 0; i < y0.length; ++i) {
+            y0[i] = field.getOne().add(i);
+        }
+
+        FieldODEStateAndDerivative<T> result = integrator.integrate(new FieldExpandableODE<T>(ode),
+                                                                    new FieldODEState<T>(t0, y0),
+                                                                    tEvent);
+        Assert.assertEquals(tEvent.getReal(), result.getTime().getReal(), epsilonT);
+        T[] y = result.getState();
+        for (int i = 0; i < y.length; ++i) {
+            Assert.assertEquals(y0[i].multiply(k[i].multiply(result.getTime().subtract(t0)).exp()).getReal(),
+                                y[i].getReal(),
+                                epsilonY);
+        }
+
+        integrator.addEventHandler(new FieldEventHandler<T>() {
+
+            public void init(FieldODEStateAndDerivative<T> state0, T t) {
+            }
+
+            public FieldODEState<T> resetState(FieldODEStateAndDerivative<T> state) {
+                return state;
+            }
+
+            public T g(FieldODEStateAndDerivative<T> state) {
+                return state.getTime().subtract(tEvent);
+            }
+
+            public Action eventOccurred(FieldODEStateAndDerivative<T> state, boolean increasing) {
+                Assert.assertEquals(tEvent.getReal(), state.getTime().getReal(), epsilonT);
+                return Action.CONTINUE;
+            }
+        }, Double.POSITIVE_INFINITY, 1.0e-20, 100);
+        result = integrator.integrate(new FieldExpandableODE<T>(ode),
+                                      new FieldODEState<T>(t0, y0),
+                                      tEvent.add(120));
+        Assert.assertEquals(tEvent.add(120).getReal(), result.getTime().getReal(), epsilonT);
+        y = result.getState();
+        for (int i = 0; i < y.length; ++i) {
+            Assert.assertEquals(y0[i].multiply(k[i].multiply(result.getTime().subtract(t0)).exp()).getReal(),
+                                y[i].getReal(),
+                                epsilonY);
+        }
+
+    }
+
+    @Test
+    public abstract void testSanityChecks();
+
+    protected <T extends RealFieldElement<T>> void doTestSanityChecks(Field<T> field)
+        throws DimensionMismatchException, NumberIsTooSmallException,
+               MaxCountExceededException, NoBracketingException {
+        RungeKuttaFieldIntegrator<T> integrator = createIntegrator(field, field.getZero().add(0.01));
+        try  {
+            TestFieldProblem1<T> pb = new TestFieldProblem1<T>(field);
+            integrator.integrate(new FieldExpandableODE<T>(pb),
+                                 new FieldODEState<T>(field.getZero(), MathArrays.buildArray(field, pb.getDimension() + 10)),
+                                 field.getOne());
+            Assert.fail("an exception should have been thrown");
+        } catch(DimensionMismatchException ie) {
+        }
+        try  {
+            TestFieldProblem1<T> pb = new TestFieldProblem1<T>(field);
+            integrator.integrate(new FieldExpandableODE<T>(pb),
+                                 new FieldODEState<T>(field.getZero(), MathArrays.buildArray(field, pb.getDimension())),
+                                 field.getZero());
+            Assert.fail("an exception should have been thrown");
+        } catch(NumberIsTooSmallException ie) {
+        }
+    }
+
+    @Test
+    public abstract void testDecreasingSteps();
+
+    protected <T extends RealFieldElement<T>> void doTestDecreasingSteps(Field<T> field,
+                                                                         final double safetyValueFactor,
+                                                                         final double safetyTimeFactor,
+                                                                         final double epsilonT)
+        throws DimensionMismatchException, NumberIsTooSmallException,
+               MaxCountExceededException, NoBracketingException {
+
+        @SuppressWarnings("unchecked")
+        TestFieldProblemAbstract<T>[] allProblems =
+                        (TestFieldProblemAbstract<T>[]) Array.newInstance(TestFieldProblemAbstract.class, 6);
+        allProblems[0] = new TestFieldProblem1<T>(field);
+        allProblems[1] = new TestFieldProblem2<T>(field);
+        allProblems[2] = new TestFieldProblem3<T>(field);
+        allProblems[3] = new TestFieldProblem4<T>(field);
+        allProblems[4] = new TestFieldProblem5<T>(field);
+        allProblems[5] = new TestFieldProblem6<T>(field);
+        for (TestFieldProblemAbstract<T> pb :  allProblems) {
+
+            T previousValueError = null;
+            T previousTimeError  = null;
+            for (int i = 4; i < 10; ++i) {
+
+                T step = pb.getFinalTime().subtract(pb.getInitialState().getTime()).multiply(FastMath.pow(2.0, -i));
+
+                RungeKuttaFieldIntegrator<T> integ = createIntegrator(field, step);
+                TestFieldProblemHandler<T> handler = new TestFieldProblemHandler<T>(pb, integ);
+                integ.addStepHandler(handler);
+                FieldEventHandler<T>[] functions = pb.getEventsHandlers();
+                for (int l = 0; l < functions.length; ++l) {
+                    integ.addEventHandler(functions[l],
+                                          Double.POSITIVE_INFINITY, 1.0e-6 * step.getReal(), 1000);
+                }
+                Assert.assertEquals(functions.length, integ.getEventHandlers().size());
+                FieldODEStateAndDerivative<T> stop = integ.integrate(new FieldExpandableODE<T>(pb),
+                                                                     pb.getInitialState(),
+                                                                     pb.getFinalTime());
+                if (functions.length == 0) {
+                    Assert.assertEquals(pb.getFinalTime().getReal(), stop.getTime().getReal(), epsilonT);
+                }
+
+                T error = handler.getMaximalValueError();
+                if (i > 4) {
+                    Assert.assertTrue(error.subtract(previousValueError.abs().multiply(safetyValueFactor)).getReal() < 0);
+                }
+                previousValueError = error;
+
+                T timeError = handler.getMaximalTimeError();
+                if (i > 4) {
+                    Assert.assertTrue(timeError.subtract(previousTimeError.abs().multiply(safetyTimeFactor)).getReal() <= 0);
+                }
+                previousTimeError = timeError;
+
+                integ.clearEventHandlers();
+                Assert.assertEquals(0, integ.getEventHandlers().size());
+            }
+
+        }
+
+    }
+
+    @Test
+    public abstract void testSmallStep();
+
+    protected <T extends RealFieldElement<T>> void doTestSmallStep(Field<T> field,
+                                                                   final double epsilonLast,
+                                                                   final double epsilonMaxValue,
+                                                                   final double epsilonMaxTime,
+                                                                   final String name)
+         throws DimensionMismatchException, NumberIsTooSmallException,
+                MaxCountExceededException, NoBracketingException {
+
+        TestFieldProblem1<T> pb = new TestFieldProblem1<T>(field);
+        T step = pb.getFinalTime().subtract(pb.getInitialState().getTime()).multiply(0.001);
+
+        RungeKuttaFieldIntegrator<T> integ = createIntegrator(field, step);
+        TestFieldProblemHandler<T> handler = new TestFieldProblemHandler<T>(pb, integ);
+        integ.addStepHandler(handler);
+        integ.integrate(new FieldExpandableODE<T>(pb), pb.getInitialState(), pb.getFinalTime());
+
+        Assert.assertEquals(0, handler.getLastError().getReal(),         epsilonLast);
+        Assert.assertEquals(0, handler.getMaximalValueError().getReal(), epsilonMaxValue);
+        Assert.assertEquals(0, handler.getMaximalTimeError().getReal(),  epsilonMaxTime);
+        Assert.assertEquals(name, integ.getName());
+
+    }
+
+    @Test
+    public abstract void testBigStep();
+
+    protected <T extends RealFieldElement<T>> void doTestBigStep(Field<T> field,
+                                                                 final double belowLast,
+                                                                 final double belowMaxValue,
+                                                                 final double epsilonMaxTime,
+                                                                 final String name)
+        throws DimensionMismatchException, NumberIsTooSmallException,
+               MaxCountExceededException, NoBracketingException {
+
+        TestFieldProblem1<T> pb = new TestFieldProblem1<T>(field);
+        T step = pb.getFinalTime().subtract(pb.getInitialState().getTime()).multiply(0.2);
+
+        RungeKuttaFieldIntegrator<T> integ = createIntegrator(field, step);
+        TestFieldProblemHandler<T> handler = new TestFieldProblemHandler<T>(pb, integ);
+        integ.addStepHandler(handler);
+        integ.integrate(new FieldExpandableODE<T>(pb), pb.getInitialState(), pb.getFinalTime());
+
+        Assert.assertTrue(handler.getLastError().getReal()         > belowLast);
+        Assert.assertTrue(handler.getMaximalValueError().getReal() > belowMaxValue);
+        Assert.assertEquals(0, handler.getMaximalTimeError().getReal(),  epsilonMaxTime);
+        Assert.assertEquals(name, integ.getName());
+
+    }
+
+    @Test
+    public abstract void testBackward();
+
+    protected <T extends RealFieldElement<T>> void doTestBackward(Field<T> field,
+                                                                  final double epsilonLast,
+                                                                  final double epsilonMaxValue,
+                                                                  final double epsilonMaxTime,
+                                                                  final String name)
+        throws DimensionMismatchException, NumberIsTooSmallException,
+               MaxCountExceededException, NoBracketingException {
+
+        TestFieldProblem5<T> pb = new TestFieldProblem5<T>(field);
+        T step = pb.getFinalTime().subtract(pb.getInitialState().getTime()).multiply(0.001).abs();
+
+        RungeKuttaFieldIntegrator<T> integ = createIntegrator(field, step);
+        TestFieldProblemHandler<T> handler = new TestFieldProblemHandler<T>(pb, integ);
+        integ.addStepHandler(handler);
+        integ.integrate(new FieldExpandableODE<T>(pb), pb.getInitialState(), pb.getFinalTime());
+
+        Assert.assertEquals(0, handler.getLastError().getReal(),         epsilonLast);
+        Assert.assertEquals(0, handler.getMaximalValueError().getReal(), epsilonMaxValue);
+        Assert.assertEquals(0, handler.getMaximalTimeError().getReal(),  epsilonMaxTime);
+        Assert.assertEquals(name, integ.getName());
+
+    }
+
+    @Test
+    public abstract void testKepler();
+
+    protected <T extends RealFieldElement<T>> void doTestKepler(Field<T> field, double expectedMaxError, double epsilon)
+        throws DimensionMismatchException, NumberIsTooSmallException,
+               MaxCountExceededException, NoBracketingException {
+
+        final TestFieldProblem3<T> pb  = new TestFieldProblem3<T>(field, field.getZero().add(0.9));
+        T step = pb.getFinalTime().subtract(pb.getInitialState().getTime()).multiply(0.0003);
+
+        RungeKuttaFieldIntegrator<T> integ = createIntegrator(field, step);
+        integ.addStepHandler(new KeplerHandler<T>(pb, expectedMaxError, epsilon));
+        integ.integrate(new FieldExpandableODE<T>(pb), pb.getInitialState(), pb.getFinalTime());
+    }
+
+    private static class KeplerHandler<T extends RealFieldElement<T>> implements FieldStepHandler<T> {
+        private T maxError;
+        private final TestFieldProblem3<T> pb;
+        private final double expectedMaxError;
+        private final double epsilon;
+        public KeplerHandler(TestFieldProblem3<T> pb, double expectedMaxError, double epsilon) {
+            this.pb               = pb;
+            this.expectedMaxError = expectedMaxError;
+            this.epsilon          = epsilon;
+            maxError = pb.getField().getZero();
+        }
+        public void init(FieldODEStateAndDerivative<T> state0, T t) {
+            maxError = pb.getField().getZero();
+        }
+        public void handleStep(FieldStepInterpolator<T> interpolator, boolean isLast)
+                        throws MaxCountExceededException {
+
+            FieldODEStateAndDerivative<T> current = interpolator.getCurrentState();
+            T[] theoreticalY  = pb.computeTheoreticalState(current.getTime());
+            T dx = current.getState()[0].subtract(theoreticalY[0]);
+            T dy = current.getState()[1].subtract(theoreticalY[1]);
+            T error = dx.multiply(dx).add(dy.multiply(dy));
+            if (error.subtract(maxError).getReal() > 0) {
+                maxError = error;
+            }
+            if (isLast) {
+                Assert.assertEquals(expectedMaxError, maxError.getReal(), epsilon);
+            }
+        }
+    }
+
+    @Test
+    public abstract void testStepSize();
+
+    protected <T extends RealFieldElement<T>> void doTestStepSize(final Field<T> field, final double epsilon)
+        throws DimensionMismatchException, NumberIsTooSmallException,
+               MaxCountExceededException, NoBracketingException {
+        final T step = field.getZero().add(1.23456);
+        RungeKuttaFieldIntegrator<T> integ = createIntegrator(field, step);
+        integ.addStepHandler(new FieldStepHandler<T>() {
+            public void handleStep(FieldStepInterpolator<T> interpolator, boolean isLast) {
+                if (! isLast) {
+                    Assert.assertEquals(step.getReal(),
+                                        interpolator.getCurrentState().getTime().subtract(interpolator.getPreviousState().getTime()).getReal(),
+                                        epsilon);
+                }
+            }
+            public void init(FieldODEStateAndDerivative<T> s0, T t) {
+            }
+        });
+        integ.integrate(new FieldExpandableODE<T>(new FirstOrderFieldDifferentialEquations<T>() {
+            public void init(T t0, T[] y0, T t) {
+            }
+            public T[] computeDerivatives(T t, T[] y) {
+                T[] dot = MathArrays.buildArray(t.getField(), 1);
+                dot[0] = t.getField().getOne();
+                return dot;
+            }
+            public int getDimension() {
+                return 1;
+            }
+        }), new FieldODEState<T>(field.getZero(), MathArrays.buildArray(field, 1)), field.getZero().add(5.0));
+    }
+
+    @Test
+    public abstract void testSingleStep();
+
+    protected <T extends RealFieldElement<T>> void doTestSingleStep(final Field<T> field, final double epsilon) {
+
+        final TestFieldProblem3<T> pb  = new TestFieldProblem3<T>(field, field.getZero().add(0.9));
+        T h = pb.getFinalTime().subtract(pb.getInitialState().getTime()).multiply(0.0003);
+
+        RungeKuttaFieldIntegrator<T> integ = createIntegrator(field, field.getZero().add(Double.NaN));
+        T   t = pb.getInitialState().getTime();
+        T[] y = pb.getInitialState().getState();
+        for (int i = 0; i < 100; ++i) {
+            y = integ.singleStep(pb, t, y, t.add(h));
+            t = t.add(h);
+        }
+        T[] yth = pb.computeTheoreticalState(t);
+        T dx = y[0].subtract(yth[0]);
+        T dy = y[1].subtract(yth[1]);
+        T error = dx.multiply(dx).add(dy.multiply(dy));
+        Assert.assertEquals(0.0, error.getReal(), epsilon);
+    }
+
+    @Test
+    public abstract void testTooLargeFirstStep();
+
+    protected <T extends RealFieldElement<T>> void doTestTooLargeFirstStep(final Field<T> field) {
+
+        RungeKuttaFieldIntegrator<T> integ = createIntegrator(field, field.getZero().add(0.5));
+        final T t0 = field.getZero();
+        final T[] y0 = MathArrays.buildArray(field, 1);
+        y0[0] = field.getOne();
+        final T t   = field.getZero().add(0.001);
+        FirstOrderFieldDifferentialEquations<T> equations = new FirstOrderFieldDifferentialEquations<T>() {
+
+            public int getDimension() {
+                return 1;
+            }
+
+            public void init(T t0, T[] y0, T t) {
+            }
+
+            public T[] computeDerivatives(T t, T[] y) {
+                Assert.assertTrue(t.getReal() >= FastMath.nextAfter(t0.getReal(), Double.NEGATIVE_INFINITY));
+                Assert.assertTrue(t.getReal() <= FastMath.nextAfter(t.getReal(),   Double.POSITIVE_INFINITY));
+                T[] yDot = MathArrays.buildArray(field, 1);
+                yDot[0] = y[0].multiply(-100.0);
+                return yDot;
+            }
+
+        };
+
+        integ.integrate(new FieldExpandableODE<T>(equations), new FieldODEState<T>(t0, y0), t);
+
+    }
+
+    @Test
+    public abstract void testUnstableDerivative();
+
+    protected <T extends RealFieldElement<T>> void doTestUnstableDerivative(Field<T> field, double epsilon) {
+      final StepFieldProblem<T> stepProblem = new StepFieldProblem<T>(field,
+                                                                      field.getZero().add(0.0),
+                                                                      field.getZero().add(1.0),
+                                                                      field.getZero().add(2.0));
+      RungeKuttaFieldIntegrator<T> integ = createIntegrator(field, field.getZero().add(0.3));
+      integ.addEventHandler(stepProblem, 1.0, 1.0e-12, 1000);
+      FieldODEStateAndDerivative<T> result = integ.integrate(new FieldExpandableODE<T>(stepProblem),
+                                                             new FieldODEState<T>(field.getZero(), MathArrays.buildArray(field, 1)),
+                                                             field.getZero().add(10.0));
+      Assert.assertEquals(8.0, result.getState()[0].getReal(), epsilon);
+    }
+
+    @Test
+    public abstract void testDerivativesConsistency();
+
+    protected <T extends RealFieldElement<T>> void doTestDerivativesConsistency(final Field<T> field, double epsilon) {
+        TestFieldProblem3<T> pb = new TestFieldProblem3<T>(field);
+        T step = pb.getFinalTime().subtract(pb.getInitialState().getTime()).multiply(0.001);
+        RungeKuttaFieldIntegrator<T> integ = createIntegrator(field, step);
+        StepInterpolatorTestUtils.checkDerivativesConsistency(integ, pb, 1.0e-10);
+    }
+
+    @Test
+    public abstract void testPartialDerivatives();
+
+    protected void doTestPartialDerivatives(final double epsilonY,
+                                            final double[] epsilonPartials) {
+
+        // parameters indices
+        final int parameters = 5;
+        final int order      = 1;
+        final int parOmega   = 0;
+        final int parTO      = 1;
+        final int parY00     = 2;
+        final int parY01     = 3;
+        final int parT       = 4;
+
+        DerivativeStructure omega = new DerivativeStructure(parameters, order, parOmega, 1.3);
+        DerivativeStructure t0    = new DerivativeStructure(parameters, order, parTO, 1.3);
+        DerivativeStructure[] y0  = new DerivativeStructure[] {
+            new DerivativeStructure(parameters, order, parY00, 3.0),
+            new DerivativeStructure(parameters, order, parY01, 4.0)
+        };
+        DerivativeStructure t     = new DerivativeStructure(parameters, order, parT, 6.0);
+        SinCos sinCos = new SinCos(omega);
+
+        RungeKuttaFieldIntegrator<DerivativeStructure> integrator =
+                        createIntegrator(omega.getField(), t.subtract(t0).multiply(0.001));
+        FieldODEStateAndDerivative<DerivativeStructure> result =
+                        integrator.integrate(new FieldExpandableODE<DerivativeStructure>(sinCos),
+                                             new FieldODEState<DerivativeStructure>(t0, y0),
+                                             t);
+
+        // check values
+        for (int i = 0; i < sinCos.getDimension(); ++i) {
+            Assert.assertEquals(sinCos.theoreticalY(t.getReal())[i], result.getState()[i].getValue(), epsilonY);
+        }
+
+        // check derivatives
+        final double[][] derivatives = sinCos.getDerivatives(t.getReal());
+        for (int i = 0; i < sinCos.getDimension(); ++i) {
+            for (int parameter = 0; parameter < parameters; ++parameter) {
+                Assert.assertEquals(derivatives[i][parameter],
+                                    dYdP(result.getState()[i], parameter),
+                                    epsilonPartials[parameter]);
+            }
+        }
+
+    }
+
+    private double dYdP(final DerivativeStructure y, final int parameter) {
+        int[] orders = new int[y.getFreeParameters()];
+        orders[parameter] = 1;
+        return y.getPartialDerivative(orders);
+    }
+
+    private static class SinCos implements FirstOrderFieldDifferentialEquations<DerivativeStructure> {
+
+        private final DerivativeStructure omega;
+        private       DerivativeStructure r;
+        private       DerivativeStructure alpha;
+
+        private double dRdY00;
+        private double dRdY01;
+        private double dAlphadOmega;
+        private double dAlphadT0;
+        private double dAlphadY00;
+        private double dAlphadY01;
+
+        protected SinCos(final DerivativeStructure omega) {
+            this.omega = omega;
+        }
+
+        public int getDimension() {
+            return 2;
+        }
+
+        public void init(final DerivativeStructure t0, final DerivativeStructure[] y0,
+                         final DerivativeStructure finalTime) {
+
+            // theoretical solution is y(t) = { r * sin(omega * t + alpha), r * cos(omega * t + alpha) }
+            // so we retrieve alpha by identification from the initial state
+            final DerivativeStructure r2 = y0[0].multiply(y0[0]).add(y0[1].multiply(y0[1]));
+
+            this.r            = r2.sqrt();
+            this.dRdY00       = y0[0].divide(r).getReal();
+            this.dRdY01       = y0[1].divide(r).getReal();
+
+            this.alpha        = y0[0].atan2(y0[1]).subtract(t0.multiply(omega));
+            this.dAlphadOmega = -t0.getReal();
+            this.dAlphadT0    = -omega.getReal();
+            this.dAlphadY00   = y0[1].divide(r2).getReal();
+            this.dAlphadY01   = y0[0].negate().divide(r2).getReal();
+
+        }
+
+        public DerivativeStructure[] computeDerivatives(final DerivativeStructure t, final DerivativeStructure[] y) {
+            return new DerivativeStructure[] {
+                omega.multiply(y[1]),
+                omega.multiply(y[0]).negate()
+            };
+        }
+
+        public double[] theoreticalY(final double t) {
+            final double theta = omega.getReal() * t + alpha.getReal();
+            return new double[] {
+                r.getReal() * FastMath.sin(theta), r.getReal() * FastMath.cos(theta)
+            };
+        }
+
+        public double[][] getDerivatives(final double t) {
+
+            // intermediate angle and state
+            final double theta        = omega.getReal() * t + alpha.getReal();
+            final double sin          = FastMath.sin(theta);
+            final double cos          = FastMath.cos(theta);
+            final double y0           = r.getReal() * sin;
+            final double y1           = r.getReal() * cos;
+
+            // partial derivatives of the state first component
+            final double dY0dOmega    =                y1 * (t + dAlphadOmega);
+            final double dY0dT0       =                y1 * dAlphadT0;
+            final double dY0dY00      = dRdY00 * sin + y1 * dAlphadY00;
+            final double dY0dY01      = dRdY01 * sin + y1 * dAlphadY01;
+            final double dY0dT        =                y1 * omega.getReal();
+
+            // partial derivatives of the state second component
+            final double dY1dOmega    =              - y0 * (t + dAlphadOmega);
+            final double dY1dT0       =              - y0 * dAlphadT0;
+            final double dY1dY00      = dRdY00 * cos - y0 * dAlphadY00;
+            final double dY1dY01      = dRdY01 * cos - y0 * dAlphadY01;
+            final double dY1dT        =              - y0 * omega.getReal();
+
+            return new double[][] {
+                { dY0dOmega, dY0dT0, dY0dY00, dY0dY01, dY0dT },
+                { dY1dOmega, dY1dT0, dY1dY00, dY1dY01, dY1dT }
+            };
+
+        }
+
+    }
+
+}

http://git-wip-us.apache.org/repos/asf/commons-math/blob/29649959/src/test/java/org/apache/commons/math3/ode/nonstiff/RungeKuttaFieldStepInterpolatorAbstractTest.java
----------------------------------------------------------------------
diff --git a/src/test/java/org/apache/commons/math3/ode/nonstiff/RungeKuttaFieldStepInterpolatorAbstractTest.java b/src/test/java/org/apache/commons/math3/ode/nonstiff/RungeKuttaFieldStepInterpolatorAbstractTest.java
new file mode 100644
index 0000000..601e7b0
--- /dev/null
+++ b/src/test/java/org/apache/commons/math3/ode/nonstiff/RungeKuttaFieldStepInterpolatorAbstractTest.java
@@ -0,0 +1,305 @@
+/*
+ * 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.AbstractIntegrator;
+import org.apache.commons.math3.ode.EquationsMapper;
+import org.apache.commons.math3.ode.ExpandableStatefulODE;
+import org.apache.commons.math3.ode.FieldEquationsMapper;
+import org.apache.commons.math3.ode.FieldExpandableODE;
+import org.apache.commons.math3.ode.FirstOrderFieldDifferentialEquations;
+import org.apache.commons.math3.ode.FieldODEStateAndDerivative;
+import org.apache.commons.math3.ode.sampling.AbstractFieldStepInterpolator;
+import org.apache.commons.math3.util.FastMath;
+import org.apache.commons.math3.util.MathArrays;
+import org.junit.Assert;
+import org.junit.Test;
+
+public abstract class RungeKuttaFieldStepInterpolatorAbstractTest {
+
+    protected abstract <T extends RealFieldElement<T>> RungeKuttaFieldStepInterpolator<T>
+        createInterpolator(Field<T> field, boolean forward, T[][] yDotK,
+                           FieldODEStateAndDerivative<T> globalPreviousState,
+                           FieldODEStateAndDerivative<T> globalCurrentState,
+                           FieldODEStateAndDerivative<T> softPreviousState,
+                           FieldODEStateAndDerivative<T> softCurrentState,
+                           FieldEquationsMapper<T> mapper);
+
+    protected abstract <T extends RealFieldElement<T>> FieldButcherArrayProvider<T>
+        createButcherArrayProvider(final Field<T> field);
+
+    @Test
+    public abstract void interpolationAtBounds();
+
+    protected <T extends RealFieldElement<T>> void doInterpolationAtBounds(final Field<T> field, double epsilon) {
+
+        RungeKuttaFieldStepInterpolator<T> interpolator = setUpInterpolator(field,
+                                                                            new SinCos<T>(field),
+                                                                            0.0, new double[] { 0.0, 1.0 }, 0.125);
+
+        Assert.assertEquals(0.0, interpolator.getPreviousState().getTime().getReal(), 1.0e-15);
+        for (int i = 0; i < 2; ++i) {
+            Assert.assertEquals(interpolator.getPreviousState().getState()[i].getReal(),
+                                interpolator.getInterpolatedState(interpolator.getPreviousState().getTime()).getState()[i].getReal(),
+                                epsilon);
+        }
+        Assert.assertEquals(0.125, interpolator.getCurrentState().getTime().getReal(), 1.0e-15);
+        for (int i = 0; i < 2; ++i) {
+            Assert.assertEquals(interpolator.getCurrentState().getState()[i].getReal(),
+                                interpolator.getInterpolatedState(interpolator.getCurrentState().getTime()).getState()[i].getReal(),
+                                epsilon);
+        }
+
+    }
+
+    @Test
+    public abstract void interpolationInside();
+
+    protected <T extends RealFieldElement<T>> void doInterpolationInside(final Field<T> field,
+                                                                         double epsilonSin, double epsilonCos) {
+
+        RungeKuttaFieldStepInterpolator<T> interpolator = setUpInterpolator(field,
+                                                                            new SinCos<T>(field),
+                                                                            0.0, new double[] { 0.0, 1.0 }, 0.0125);
+
+        int n = 100;
+        double maxErrorSin = 0;
+        double maxErrorCos = 0;
+        for (int i = 0; i <= n; ++i) {
+            T t =     interpolator.getPreviousState().getTime().multiply(n - i).
+                  add(interpolator.getCurrentState().getTime().multiply(i)).
+                  divide(n);
+            FieldODEStateAndDerivative<T> state = interpolator.getInterpolatedState(t);
+            maxErrorSin = FastMath.max(maxErrorSin, state.getState()[0].subtract(t.sin()).abs().getReal());
+            maxErrorCos = FastMath.max(maxErrorCos, state.getState()[1].subtract(t.cos()).abs().getReal());
+        }
+        Assert.assertEquals(0.0, maxErrorSin, epsilonSin);
+        Assert.assertEquals(0.0, maxErrorCos, epsilonCos);
+
+    }
+
+    @Test
+    public abstract void nonFieldInterpolatorConsistency();
+
+    protected <T extends RealFieldElement<T>> void doNonFieldInterpolatorConsistency(final Field<T> field,
+                                                                                     double epsilonSin, double epsilonCos,
+                                                                                     double epsilonSinDot, double epsilonCosDot) {
+
+        FirstOrderFieldDifferentialEquations<T> eqn = new SinCos<T>(field);
+        RungeKuttaFieldStepInterpolator<T> fieldInterpolator =
+                        setUpInterpolator(field, eqn, 0.0, new double[] { 0.0, 1.0 }, 0.125);
+        RungeKuttaStepInterpolator regularInterpolator = convertInterpolator(fieldInterpolator, eqn);
+
+        int n = 100;
+        double maxErrorSin    = 0;
+        double maxErrorCos    = 0;
+        double maxErrorSinDot = 0;
+        double maxErrorCosDot = 0;
+        for (int i = 0; i <= n; ++i) {
+
+            T t =     fieldInterpolator.getPreviousState().getTime().multiply(n - i).
+                  add(fieldInterpolator.getCurrentState().getTime().multiply(i)).
+                  divide(n);
+
+            FieldODEStateAndDerivative<T> state = fieldInterpolator.getInterpolatedState(t);
+            T[] fieldY    = state.getState();
+            T[] fieldYDot = state.getDerivative();
+
+            regularInterpolator.setInterpolatedTime(t.getReal());
+            double[] regularY     = regularInterpolator.getInterpolatedState();
+            double[] regularYDot  = regularInterpolator.getInterpolatedDerivatives();
+
+            maxErrorSin    = FastMath.max(maxErrorSin,    fieldY[0].subtract(regularY[0]).abs().getReal());
+            maxErrorCos    = FastMath.max(maxErrorCos,    fieldY[1].subtract(regularY[1]).abs().getReal());
+            maxErrorSinDot = FastMath.max(maxErrorSinDot, fieldYDot[0].subtract(regularYDot[0]).abs().getReal());
+            maxErrorCosDot = FastMath.max(maxErrorCosDot, fieldYDot[1].subtract(regularYDot[1]).abs().getReal());
+
+        }
+        Assert.assertEquals(0.0, maxErrorSin,    epsilonSin);
+        Assert.assertEquals(0.0, maxErrorCos,    epsilonCos);
+        Assert.assertEquals(0.0, maxErrorSinDot, epsilonSinDot);
+        Assert.assertEquals(0.0, maxErrorCosDot, epsilonCosDot);
+
+    }
+
+    private <T extends RealFieldElement<T>>
+    RungeKuttaFieldStepInterpolator<T> setUpInterpolator(final Field<T> field,
+                                                         final FirstOrderFieldDifferentialEquations<T> eqn,
+                                                         final double t0, final double[] y0,
+                                                         final double t1) {
+
+        // get the Butcher arrays from the field integrator
+        FieldButcherArrayProvider<T> provider = createButcherArrayProvider(field);
+        T[][] a = provider.getA();
+        T[]   b = provider.getB();
+        T[]   c = provider.getC();
+
+        // store initial state
+        T     t          = field.getZero().add(t0);
+        T[]   fieldY     = MathArrays.buildArray(field, eqn.getDimension());
+        T[][] fieldYDotK = MathArrays.buildArray(field, b.length, -1);
+        for (int i = 0; i < y0.length; ++i) {
+            fieldY[i] = field.getZero().add(y0[i]);
+        }
+        fieldYDotK[0] = eqn.computeDerivatives(t, fieldY);
+        FieldODEStateAndDerivative<T> s0 = new FieldODEStateAndDerivative<T>(t, fieldY, fieldYDotK[0]);
+
+        // perform one integration step, in order to get consistent derivatives
+        T h = field.getZero().add(t1 - t0);
+        for (int k = 0; k < a.length; ++k) {
+            for (int i = 0; i < y0.length; ++i) {
+                fieldY[i] = field.getZero().add(y0[i]);
+                for (int s = 0; s <= k; ++s) {
+                    fieldY[i] = fieldY[i].add(h.multiply(a[k][s].multiply(fieldYDotK[s][i])));
+                }
+            }
+            fieldYDotK[k + 1] = eqn.computeDerivatives(h.multiply(c[k]).add(t0), fieldY);
+        }
+
+        // store state at step end
+        t = field.getZero().add(t1);
+        for (int i = 0; i < y0.length; ++i) {
+            fieldY[i] = field.getZero().add(y0[i]);
+            for (int s = 0; s < b.length; ++s) {
+                fieldY[i] = fieldY[i].add(h.multiply(b[s].multiply(fieldYDotK[s][i])));
+            }
+        }
+        FieldODEStateAndDerivative<T> s1 = new FieldODEStateAndDerivative<T>(t, fieldY,
+                                                                             eqn.computeDerivatives(t, fieldY));
+
+        return createInterpolator(field, t1 > t0, fieldYDotK, s0, s1, s0, s1,
+                                  new FieldExpandableODE<T>(eqn).getMapper());
+
+    }
+
+    private <T extends RealFieldElement<T>>
+    RungeKuttaStepInterpolator convertInterpolator(final RungeKuttaFieldStepInterpolator<T> fieldInterpolator,
+                                                   final FirstOrderFieldDifferentialEquations<T> eqn) {
+
+        RungeKuttaStepInterpolator regularInterpolator = null;
+        try {
+
+            String interpolatorName = fieldInterpolator.getClass().getName();
+            String integratorName = interpolatorName.replaceAll("Field", "");
+            @SuppressWarnings("unchecked")
+            Class<RungeKuttaStepInterpolator> clz = (Class<RungeKuttaStepInterpolator>) Class.forName(integratorName);
+            regularInterpolator = clz.newInstance();
+
+            double[][] yDotArray = null;
+            java.lang.reflect.Field fYD = RungeKuttaFieldStepInterpolator.class.getDeclaredField("yDotK");
+            fYD.setAccessible(true);
+            @SuppressWarnings("unchecked")
+            T[][] fieldYDotk = (T[][]) fYD.get(fieldInterpolator);
+            yDotArray = new double[fieldYDotk.length][];
+            for (int i = 0; i < yDotArray.length; ++i) {
+                yDotArray[i] = new double[fieldYDotk[i].length];
+                for (int j = 0; j < yDotArray[i].length; ++j) {
+                    yDotArray[i][j] = fieldYDotk[i][j].getReal();
+                }
+            }
+            double[] y = new double[yDotArray[0].length];
+
+            EquationsMapper primaryMapper = null;
+            EquationsMapper[] secondaryMappers = null;
+            java.lang.reflect.Field fMapper = AbstractFieldStepInterpolator.class.getDeclaredField("mapper");
+            fMapper.setAccessible(true);
+            @SuppressWarnings("unchecked")
+            FieldEquationsMapper<T> mapper = (FieldEquationsMapper<T>) fMapper.get(fieldInterpolator);
+            java.lang.reflect.Field fStart = FieldEquationsMapper.class.getDeclaredField("start");
+            fStart.setAccessible(true);
+            int[] start = (int[]) fStart.get(mapper);
+            primaryMapper = new EquationsMapper(start[0], start[1]);
+            secondaryMappers = new EquationsMapper[mapper.getNumberOfEquations() - 1];
+            for (int i = 0; i < secondaryMappers.length; ++i) {
+                secondaryMappers[i] = new EquationsMapper(start[i + 1], start[i + 2]);
+            }
+
+            AbstractIntegrator dummyIntegrator = new AbstractIntegrator("dummy") {
+                @Override
+                public void integrate(ExpandableStatefulODE equations, double t) {
+                    Assert.fail("this method should not be called");
+                }
+                @Override
+                public void computeDerivatives(final double t, final double[] y, final double[] yDot) {
+                    T fieldT = fieldInterpolator.getCurrentState().getTime().getField().getZero().add(t);
+                    T[] fieldY = MathArrays.buildArray(fieldInterpolator.getCurrentState().getTime().getField(), y.length);
+                    for (int i = 0; i < y.length; ++i) {
+                        fieldY[i] = fieldInterpolator.getCurrentState().getTime().getField().getZero().add(y[i]);
+                    }
+                    T[] fieldYDot = eqn.computeDerivatives(fieldT, fieldY);
+                    for (int i = 0; i < yDot.length; ++i) {
+                        yDot[i] = fieldYDot[i].getReal();
+                    }
+                }
+            };
+            regularInterpolator.reinitialize(dummyIntegrator, y, yDotArray,
+                                             fieldInterpolator.isForward(),
+                                             primaryMapper, secondaryMappers);
+
+            T[] fieldPreviousY = fieldInterpolator.getPreviousState().getState();
+            for (int i = 0; i < y.length; ++i) {
+                y[i] = fieldPreviousY[i].getReal();
+            }
+            regularInterpolator.storeTime(fieldInterpolator.getPreviousState().getTime().getReal());
+
+            regularInterpolator.shift();
+
+            T[] fieldCurrentY = fieldInterpolator.getCurrentState().getState();
+            for (int i = 0; i < y.length; ++i) {
+                y[i] = fieldCurrentY[i].getReal();
+            }
+            regularInterpolator.storeTime(fieldInterpolator.getCurrentState().getTime().getReal());
+
+        } catch (ClassNotFoundException cnfe) {
+            Assert.fail(cnfe.getLocalizedMessage());
+        } catch (InstantiationException ie) {
+            Assert.fail(ie.getLocalizedMessage());
+        } catch (IllegalAccessException iae) {
+            Assert.fail(iae.getLocalizedMessage());
+        } catch (NoSuchFieldException nsfe) {
+            Assert.fail(nsfe.getLocalizedMessage());
+        } catch (IllegalArgumentException iae) {
+            Assert.fail(iae.getLocalizedMessage());
+        }
+
+        return regularInterpolator;
+
+    }
+
+    private static class SinCos<T extends RealFieldElement<T>> implements FirstOrderFieldDifferentialEquations<T> {
+        private final Field<T> field;
+        protected SinCos(final Field<T> field) {
+            this.field = field;
+        }
+        public int getDimension() {
+            return 2;
+        }
+        public void init(final T t0, final T[] y0, final T finalTime) {
+        }
+        public T[] computeDerivatives(final T t, final T[] y) {
+            T[] yDot = MathArrays.buildArray(field, 2);
+            yDot[0] = y[1];
+            yDot[1] = y[0].negate();
+            return yDot;
+        }
+    }
+
+}

http://git-wip-us.apache.org/repos/asf/commons-math/blob/29649959/src/test/java/org/apache/commons/math3/ode/nonstiff/ThreeEighthesFieldIntegratorTest.java
----------------------------------------------------------------------
diff --git a/src/test/java/org/apache/commons/math3/ode/nonstiff/ThreeEighthesFieldIntegratorTest.java b/src/test/java/org/apache/commons/math3/ode/nonstiff/ThreeEighthesFieldIntegratorTest.java
index 700661d..971dac8 100644
--- a/src/test/java/org/apache/commons/math3/ode/nonstiff/ThreeEighthesFieldIntegratorTest.java
+++ b/src/test/java/org/apache/commons/math3/ode/nonstiff/ThreeEighthesFieldIntegratorTest.java
@@ -22,7 +22,7 @@ import org.apache.commons.math3.Field;
 import org.apache.commons.math3.RealFieldElement;
 import org.apache.commons.math3.util.Decimal64Field;
 
-public class ThreeEighthesFieldIntegratorTest extends AbstractRungeKuttaFieldIntegratorTest {
+public class ThreeEighthesFieldIntegratorTest extends RungeKuttaFieldIntegratorAbstractTest {
 
     protected <T extends RealFieldElement<T>> RungeKuttaFieldIntegrator<T>
     createIntegrator(Field<T> field, T step) {

http://git-wip-us.apache.org/repos/asf/commons-math/blob/29649959/src/test/java/org/apache/commons/math3/ode/nonstiff/ThreeEighthesFieldStepInterpolatorTest.java
----------------------------------------------------------------------
diff --git a/src/test/java/org/apache/commons/math3/ode/nonstiff/ThreeEighthesFieldStepInterpolatorTest.java b/src/test/java/org/apache/commons/math3/ode/nonstiff/ThreeEighthesFieldStepInterpolatorTest.java
index f1a2d28..f326a2b 100644
--- a/src/test/java/org/apache/commons/math3/ode/nonstiff/ThreeEighthesFieldStepInterpolatorTest.java
+++ b/src/test/java/org/apache/commons/math3/ode/nonstiff/ThreeEighthesFieldStepInterpolatorTest.java
@@ -25,7 +25,7 @@ import org.apache.commons.math3.ode.FieldODEStateAndDerivative;
 import org.apache.commons.math3.util.Decimal64Field;
 import org.junit.Test;
 
-public class ThreeEighthesFieldStepInterpolatorTest extends AbstractRungeKuttaFieldStepInterpolatorTest {
+public class ThreeEighthesFieldStepInterpolatorTest extends RungeKuttaFieldStepInterpolatorAbstractTest {
 
     protected <T extends RealFieldElement<T>> RungeKuttaFieldStepInterpolator<T>
     createInterpolator(Field<T> field, boolean forward, T[][] yDotK,


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