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package org.apache.commons.math3.optimization.fitting;
import java.util.Random;
import org.apache.commons.math3.analysis.polynomials.PolynomialFunction;
import org.apache.commons.math3.analysis.polynomials.PolynomialFunction.Parametric;
import org.apache.commons.math3.exception.ConvergenceException;
import org.apache.commons.math3.exception.TooManyEvaluationsException;
import org.apache.commons.math3.optimization.DifferentiableMultivariateVectorOptimizer;
import org.apache.commons.math3.optimization.general.GaussNewtonOptimizer;
import org.apache.commons.math3.optimization.general.LevenbergMarquardtOptimizer;
import org.apache.commons.math3.optimization.SimpleVectorValueChecker;
import org.apache.commons.math3.util.FastMath;
import org.apache.commons.math3.distribution.RealDistribution;
import org.apache.commons.math3.distribution.UniformRealDistribution;
import org.apache.commons.math3.TestUtils;
import org.junit.Test;
import org.junit.Assert;
/**
* Test for class {@link CurveFitter} where the function to fit is a
* polynomial.
*/
@Deprecated
public class PolynomialFitterTest {
@Test
public void testFit() {
final RealDistribution rng = new UniformRealDistribution(-100, 100);
rng.reseedRandomGenerator(64925784252L);
final LevenbergMarquardtOptimizer optim = new LevenbergMarquardtOptimizer();
final PolynomialFitter fitter = new PolynomialFitter(optim);
final double[] coeff = { 12.9, -3.4, 2.1 }; // 12.9 - 3.4 x + 2.1 x^2
final PolynomialFunction f = new PolynomialFunction(coeff);
// Collect data from a known polynomial.
for (int i = 0; i < 100; i++) {
final double x = rng.sample();
fitter.addObservedPoint(x, f.value(x));
}
// Start fit from initial guesses that are far from the optimal values.
final double[] best = fitter.fit(new double[] { -1e-20, 3e15, -5e25 });
TestUtils.assertEquals("best != coeff", coeff, best, 1e-12);
}
@Test
public void testNoError() {
Random randomizer = new Random(64925784252l);
for (int degree = 1; degree < 10; ++degree) {
PolynomialFunction p = buildRandomPolynomial(degree, randomizer);
PolynomialFitter fitter = new PolynomialFitter(new LevenbergMarquardtOptimizer());
for (int i = 0; i <= degree; ++i) {
fitter.addObservedPoint(1.0, i, p.value(i));
}
final double[] init = new double[degree + 1];
PolynomialFunction fitted = new PolynomialFunction(fitter.fit(init));
for (double x = -1.0; x < 1.0; x += 0.01) {
double error = FastMath.abs(p.value(x) - fitted.value(x)) /
(1.0 + FastMath.abs(p.value(x)));
Assert.assertEquals(0.0, error, 1.0e-6);
}
}
}
@Test
public void testSmallError() {
Random randomizer = new Random(53882150042l);
double maxError = 0;
for (int degree = 0; degree < 10; ++degree) {
PolynomialFunction p = buildRandomPolynomial(degree, randomizer);
PolynomialFitter fitter = new PolynomialFitter(new LevenbergMarquardtOptimizer());
for (double x = -1.0; x < 1.0; x += 0.01) {
fitter.addObservedPoint(1.0, x,
p.value(x) + 0.1 * randomizer.nextGaussian());
}
final double[] init = new double[degree + 1];
PolynomialFunction fitted = new PolynomialFunction(fitter.fit(init));
for (double x = -1.0; x < 1.0; x += 0.01) {
double error = FastMath.abs(p.value(x) - fitted.value(x)) /
(1.0 + FastMath.abs(p.value(x)));
maxError = FastMath.max(maxError, error);
Assert.assertTrue(FastMath.abs(error) < 0.1);
}
}
Assert.assertTrue(maxError > 0.01);
}
@Test
public void testMath798() {
final double tol = 1e-14;
final SimpleVectorValueChecker checker = new SimpleVectorValueChecker(tol, tol);
final double[] init = new double[] { 0, 0 };
final int maxEval = 3;
final double[] lm = doMath798(new LevenbergMarquardtOptimizer(checker), maxEval, init);
final double[] gn = doMath798(new GaussNewtonOptimizer(checker), maxEval, init);
for (int i = 0; i <= 1; i++) {
Assert.assertEquals(lm[i], gn[i], tol);
}
}
/**
* This test shows that the user can set the maximum number of iterations
* to avoid running for too long.
* But in the test case, the real problem is that the tolerance is way too
* stringent.
*/
@Test(expected=TooManyEvaluationsException.class)
public void testMath798WithToleranceTooLow() {
final double tol = 1e-100;
final SimpleVectorValueChecker checker = new SimpleVectorValueChecker(tol, tol);
final double[] init = new double[] { 0, 0 };
final int maxEval = 10000; // Trying hard to fit.
doMath798(new GaussNewtonOptimizer(checker), maxEval, init);
}
/**
* This test shows that the user can set the maximum number of iterations
* to avoid running for too long.
* Even if the real problem is that the tolerance is way too stringent, it
* is possible to get the best solution so far, i.e. a checker will return
* the point when the maximum iteration count has been reached.
*/
@Test
public void testMath798WithToleranceTooLowButNoException() {
final double tol = 1e-100;
final double[] init = new double[] { 0, 0 };
final int maxEval = 10000; // Trying hard to fit.
final SimpleVectorValueChecker checker = new SimpleVectorValueChecker(tol, tol, maxEval);
final double[] lm = doMath798(new LevenbergMarquardtOptimizer(checker), maxEval, init);
final double[] gn = doMath798(new GaussNewtonOptimizer(checker), maxEval, init);
for (int i = 0; i <= 1; i++) {
Assert.assertEquals(lm[i], gn[i], 1e-15);
}
}
/**
* @param optimizer Optimizer.
* @param maxEval Maximum number of function evaluations.
* @param init First guess.
* @return the solution found by the given optimizer.
*/
private double[] doMath798(DifferentiableMultivariateVectorOptimizer optimizer,
int maxEval,
double[] init) {
final CurveFitter<Parametric> fitter = new CurveFitter<Parametric>(optimizer);
fitter.addObservedPoint(-0.2, -7.12442E-13);
fitter.addObservedPoint(-0.199, -4.33397E-13);
fitter.addObservedPoint(-0.198, -2.823E-13);
fitter.addObservedPoint(-0.197, -1.40405E-13);
fitter.addObservedPoint(-0.196, -7.80821E-15);
fitter.addObservedPoint(-0.195, 6.20484E-14);
fitter.addObservedPoint(-0.194, 7.24673E-14);
fitter.addObservedPoint(-0.193, 1.47152E-13);
fitter.addObservedPoint(-0.192, 1.9629E-13);
fitter.addObservedPoint(-0.191, 2.12038E-13);
fitter.addObservedPoint(-0.19, 2.46906E-13);
fitter.addObservedPoint(-0.189, 2.77495E-13);
fitter.addObservedPoint(-0.188, 2.51281E-13);
fitter.addObservedPoint(-0.187, 2.64001E-13);
fitter.addObservedPoint(-0.186, 2.8882E-13);
fitter.addObservedPoint(-0.185, 3.13604E-13);
fitter.addObservedPoint(-0.184, 3.14248E-13);
fitter.addObservedPoint(-0.183, 3.1172E-13);
fitter.addObservedPoint(-0.182, 3.12912E-13);
fitter.addObservedPoint(-0.181, 3.06761E-13);
fitter.addObservedPoint(-0.18, 2.8559E-13);
fitter.addObservedPoint(-0.179, 2.86806E-13);
fitter.addObservedPoint(-0.178, 2.985E-13);
fitter.addObservedPoint(-0.177, 2.67148E-13);
fitter.addObservedPoint(-0.176, 2.94173E-13);
fitter.addObservedPoint(-0.175, 3.27528E-13);
fitter.addObservedPoint(-0.174, 3.33858E-13);
fitter.addObservedPoint(-0.173, 2.97511E-13);
fitter.addObservedPoint(-0.172, 2.8615E-13);
fitter.addObservedPoint(-0.171, 2.84624E-13);
final double[] coeff = fitter.fit(maxEval,
new PolynomialFunction.Parametric(),
init);
return coeff;
}
@Test
public void testRedundantSolvable() {
// Levenberg-Marquardt should handle redundant information gracefully
checkUnsolvableProblem(new LevenbergMarquardtOptimizer(), true);
}
@Test
public void testRedundantUnsolvable() {
// Gauss-Newton should not be able to solve redundant information
checkUnsolvableProblem(new GaussNewtonOptimizer(true, new SimpleVectorValueChecker(1e-15, 1e-15)), false);
}
@Test
public void testLargeSample() {
Random randomizer = new Random(0x5551480dca5b369bl);
double maxError = 0;
for (int degree = 0; degree < 10; ++degree) {
PolynomialFunction p = buildRandomPolynomial(degree, randomizer);
PolynomialFitter fitter = new PolynomialFitter(new LevenbergMarquardtOptimizer());
for (int i = 0; i < 40000; ++i) {
double x = -1.0 + i / 20000.0;
fitter.addObservedPoint(1.0, x,
p.value(x) + 0.1 * randomizer.nextGaussian());
}
final double[] init = new double[degree + 1];
PolynomialFunction fitted = new PolynomialFunction(fitter.fit(init));
for (double x = -1.0; x < 1.0; x += 0.01) {
double error = FastMath.abs(p.value(x) - fitted.value(x)) /
(1.0 + FastMath.abs(p.value(x)));
maxError = FastMath.max(maxError, error);
Assert.assertTrue(FastMath.abs(error) < 0.01);
}
}
Assert.assertTrue(maxError > 0.001);
}
private void checkUnsolvableProblem(DifferentiableMultivariateVectorOptimizer optimizer,
boolean solvable) {
Random randomizer = new Random(1248788532l);
for (int degree = 0; degree < 10; ++degree) {
PolynomialFunction p = buildRandomPolynomial(degree, randomizer);
PolynomialFitter fitter = new PolynomialFitter(optimizer);
// reusing the same point over and over again does not bring
// information, the problem cannot be solved in this case for
// degrees greater than 1 (but one point is sufficient for
// degree 0)
for (double x = -1.0; x < 1.0; x += 0.01) {
fitter.addObservedPoint(1.0, 0.0, p.value(0.0));
}
try {
final double[] init = new double[degree + 1];
fitter.fit(init);
Assert.assertTrue(solvable || (degree == 0));
} catch(ConvergenceException e) {
Assert.assertTrue((! solvable) && (degree > 0));
}
}
}
private PolynomialFunction buildRandomPolynomial(int degree, Random randomizer) {
final double[] coefficients = new double[degree + 1];
for (int i = 0; i <= degree; ++i) {
coefficients[i] = randomizer.nextGaussian();
}
return new PolynomialFunction(coefficients);
}
}