CaRMtl/rene/zirkel/expression/ConvexMin.java
2018-09-04 22:51:42 -04:00

78 lines
2.1 KiB
Java

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