Java tutorial
/* GeoGebra - Dynamic Mathematics for Everyone http://www.geogebra.org This file is part of GeoGebra. This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation. */ package geogebra.kernel; import geogebra.kernel.arithmetic.NumberValue; import geogebra.kernel.roots.RealRootAdapter; import geogebra.kernel.roots.RealRootFunction; import org.apache.commons.math.ConvergenceException; import org.apache.commons.math.FunctionEvaluationException; import org.apache.commons.math.MaxIterationsExceededException; import org.apache.commons.math.analysis.integration.LegendreGaussIntegrator; /** * Integral of a function (GeoFunction) * * @author Markus Hohenwarter */ public class AlgoIntegralDefinite extends AlgoElementCAS implements AlgoDrawInformation { private static final long serialVersionUID = 1L; private GeoFunction f; // input private NumberValue a, b; //input private GeoBoolean evaluate; //input private GeoElement ageo, bgeo; private GeoNumeric n; // output g = integral(f(x), x, a, b) // for symbolic integration private GeoFunction symbIntegral; // for numerical adaptive GaussQuad integration private static final int FIRST_ORDER = 3; private static final int SECOND_ORDER = 5; private static final int MAX_ITER = 5; private static LegendreGaussIntegrator firstGauss, secondGauss; private static int adaptiveGaussQuadCounter = 0; private static final int MAX_GAUSS_QUAD_CALLS = 500; public AlgoIntegralDefinite(Construction cons, String label, GeoFunction f, NumberValue a, NumberValue b) { this(cons, f, a, b, null); n.setLabel(label); } public AlgoIntegralDefinite(Construction cons, String label, GeoFunction f, NumberValue a, NumberValue b, GeoBoolean evaluate) { this(cons, f, a, b, evaluate); n.setLabel(label); } AlgoIntegralDefinite(Construction cons, GeoFunction f, NumberValue a, NumberValue b, GeoBoolean evaluate) { super(cons); this.f = f; n = new GeoNumeric(cons); // output this.a = a; this.b = b; ageo = a.toGeoElement(); bgeo = b.toGeoElement(); this.evaluate = evaluate; // create helper algorithm for symbolic integral // don't use symbolic integral for conditional functions // or if it should not be evaluated (i.e. a shade-only integral) if ((evaluate != null && evaluate.getBoolean()) && !f.isGeoFunctionConditional()) { AlgoCasIntegral algoInt = new AlgoCasIntegral(cons, f, null); symbIntegral = (GeoFunction) algoInt.getResult(); // make sure algo is removed properly geo = f; cons.removeFromConstructionList(algoInt); } setInputOutput(); // for AlgoElement compute(); n.setDrawable(true); } public AlgoIntegralDefinite(GeoFunction f, NumberValue a, NumberValue b, GeoBoolean evaluate) { this.f = f; this.a = a; this.b = b; this.evaluate = evaluate; } public String getClassName() { return "AlgoIntegralDefinite"; } // for AlgoElement protected void setInputOutput() { if (evaluate == null) { input = new GeoElement[3]; input[0] = f; input[1] = ageo; input[2] = bgeo; } else { input = new GeoElement[4]; input[0] = f; input[1] = ageo; input[2] = bgeo; input[3] = evaluate; } setOutputLength(1); setOutput(0, n); setDependencies(); // done by AlgoElement } public GeoNumeric getIntegral() { return n; } double getIntegralValue() { return n.value; } public GeoFunction getFunction() { return f; } public NumberValue getA() { return a; } public NumberValue getB() { return b; } protected final void compute() { if (!f.isDefined() || !ageo.isDefined() || !bgeo.isDefined()) { n.setUndefined(); return; } // check for equal bounds double lowerLimit = a.getDouble(); double upperLimit = b.getDouble(); if (Kernel.isEqual(lowerLimit, upperLimit)) { n.setValue(0); return; } // check if f(a) and f(b) are defined double fa = f.evaluate(lowerLimit); double fb = f.evaluate(upperLimit); if (Double.isNaN(fa) || Double.isInfinite(fa) || Double.isNaN(fb) || Double.isInfinite(fb)) { n.setUndefined(); return; } // return if it should not be evaluated (i.e. is shade-only) if (evaluate != null && !evaluate.getBoolean()) { n.setValue(0); return; } /* * Try to use symbolic integral * * We only do this for functions that do NOT include divisions by their variable. * Otherwise there might be problems like: * Integral[ 1/x, -2, -1 ] would be undefined (log(-1) - log(-2)) * Integral[ 1/x^2, -1, 1 ] would be defined (-2) */ if (symbIntegral != null && symbIntegral.isDefined() && !f.includesDivisionByVar()) { double val = symbIntegral.evaluate(upperLimit) - symbIntegral.evaluate(lowerLimit); n.setValue(val); if (n.isDefined()) return; } // numerical integration // max_error = ACCURACY; // current maximum error //maxstep = 0; double integral = numericIntegration(f, lowerLimit, upperLimit); n.setValue(integral); /* Application.debug("***\nsteps: " + maxstep); Application.debug("max_error: " + max_error); */ } // private int maxstep; /** * Computes integral of function fun in interval a, b using an adaptive Gauss * quadrature approach. * @param fun function * @param a lower bound * @param b upper bound * @return integral value */ public static double numericIntegration(RealRootFunction fun, double a, double b) { adaptiveGaussQuadCounter = 0; if (a > b) { return -doAdaptiveGaussQuad(fun, b, a); } else { return doAdaptiveGaussQuad(fun, a, b); } //System.out.println("calls: " + adaptiveGaussQuadCounter); } private static double doAdaptiveGaussQuad(RealRootFunction fun, double a, double b) { if (++adaptiveGaussQuadCounter > MAX_GAUSS_QUAD_CALLS) { return Double.NaN; } // init GaussQuad classes for numerical integration if (firstGauss == null) { firstGauss = new LegendreGaussIntegrator(FIRST_ORDER, MAX_ITER); secondGauss = new LegendreGaussIntegrator(SECOND_ORDER, MAX_ITER); } double firstSum = 0; double secondSum = 0; boolean error = false; // integrate using gauss quadrature try { firstSum = firstGauss.integrate(new RealRootAdapter(fun), a, b); if (Double.isNaN(firstSum)) return Double.NaN; secondSum = secondGauss.integrate(new RealRootAdapter(fun), a, b); if (Double.isNaN(secondSum)) return Double.NaN; } catch (MaxIterationsExceededException e) { error = true; } catch (ConvergenceException e) { error = true; } catch (FunctionEvaluationException e) { return Double.NaN; } catch (IllegalArgumentException e) { return Double.NaN; } //if (!error) Application.debug(a+" "+b+" "+(firstSum - secondSum), Kernel.isEqual(firstSum, secondSum, Kernel.STANDARD_PRECISION) ? 1 : 0); //else Application.debug(a+" "+b+" error",1); // check if both results are equal boolean equal = !error && Kernel.isEqual(firstSum, secondSum, Kernel.STANDARD_PRECISION); if (equal) { // success return secondSum; } else { double mid = (a + b) / 2; double left = doAdaptiveGaussQuad(fun, a, mid); if (Double.isNaN(left)) return Double.NaN; else return left + doAdaptiveGaussQuad(fun, mid, b); } } final public String toString() { // Michael Borcherds 2008-03-30 // simplified to allow better Chinese translation return app.getPlain("IntegralOfAfromBtoC", f.getLabel(), ageo.getLabel(), bgeo.getLabel()); } public AlgoDrawInformation copy() { if (evaluate != null) return new AlgoIntegralDefinite((GeoFunction) f.copy(), (NumberValue) a.deepCopy(kernel), (NumberValue) b.deepCopy(kernel), (GeoBoolean) evaluate.copy()); return new AlgoIntegralDefinite((GeoFunction) f.copy(), (NumberValue) a.deepCopy(kernel), (NumberValue) b.deepCopy(kernel), null); } }