78 lines
2.1 KiB
Java
78 lines
2.1 KiB
Java
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/*
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Copyright 2006 Rene Grothmann, modified by Eric Hakenholz
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This file is part of C.a.R. software.
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C.a.R. is a free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, version 3 of the License.
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C.a.R. is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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package rene.zirkel.expression;
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import rene.zirkel.construction.ConstructionException;
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import rene.zirkel.objects.Evaluator;
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public class ConvexMin {
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public static double computeMin(final Evaluator F, double a, double b,
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final double eps) throws ConstructionException {
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final double lambda = (Math.sqrt(5) - 1) / 2;
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double x2 = lambda * a + (1 - lambda) * b;
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double y2 = F.evaluateF(x2);
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double x3 = (1 - lambda) * a + lambda * b;
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double y3 = F.evaluateF(x3);
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while (b - a > eps) {
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if (y2 < y3) {
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b = x3;
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x3 = x2;
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y3 = y2;
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x2 = lambda * a + (1 - lambda) * b;
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y2 = F.evaluateF(x2);
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} else {
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a = x2;
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x2 = x3;
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y2 = y3;
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x3 = (1 - lambda) * a + lambda * b;
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y3 = F.evaluateF(x3);
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}
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}
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return (a + b) / 2;
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}
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public static double computeMax(final Evaluator F, double a, double b,
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final double eps) throws ConstructionException {
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final double lambda = (Math.sqrt(5) - 1) / 2;
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double x2 = lambda * a + (1 - lambda) * b;
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double y2 = F.evaluateF(x2);
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double x3 = (1 - lambda) * a + lambda * b;
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double y3 = F.evaluateF(x3);
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while (b - a > eps) {
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if (y2 > y3) {
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b = x3;
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x3 = x2;
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y3 = y2;
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x2 = lambda * a + (1 - lambda) * b;
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y2 = F.evaluateF(x2);
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} else {
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a = x2;
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x2 = x3;
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y2 = y3;
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x3 = (1 - lambda) * a + lambda * b;
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y3 = F.evaluateF(x3);
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}
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}
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return (a + b) / 2;
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}
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}
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