/*
* Encog(tm) Core v3.4 - Java Version
* http://www.heatonresearch.com/encog/
* https://github.com/encog/encog-java-core
* Copyright 2008-2016 Heaton Research, Inc.
*
* Licensed 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.
*
* For more information on Heaton Research copyrights, licenses
* and trademarks visit:
* http://www.heatonresearch.com/copyright
*/
package org.encog.mathutil;
import java.util.Random;
/**
* Basic vector algebra operators.
* Vectors are represented as arrays of doubles.
*
* This class was created to support the calculations
* in the PSO algorithm.
*
* This class is thread safe.
*
* Contributed by:
* Geoffroy Noel
* https://github.com/goffer-looney
*
* @author Geoffroy Noel
*/
public class VectorAlgebra {
static Random rand = new Random();
/**
* v1 = v1 + v2
*
* @param v1 an array of doubles
* @param v2 an array of doubles
*/
public void add(double[] v1, double[] v2) {
for (int i = 0; i < v1.length; i++) {
v1[i] += v2[i];
}
}
/**
* v1 = v1 - v2
*
* @param v1 an array of doubles
* @param v2 an array of doubles
*/
public void sub(double[] v1, double[] v2) {
for (int i = 0; i < v1.length; i++) {
v1[i] -= v2[i];
}
}
/**
* v = -v
*
* @param v an array of doubles
*/
public void neg(double[] v) {
for (int i = 0; i < v.length; i++) {
v[i] = -v[i];
}
}
/**
* v = k * U(0,1) * v
*
* The components of the vector are multiplied
* by k and a random number.
* A new random number is generated for each
* component.
* Thread-safety depends on Random.nextDouble()
*
* @param v an array of doubles.
* @param k a scalar.
*/
public void mulRand(double[] v, double k) {
for (int i = 0; i < v.length; i++) {
v[i] *= k * rand.nextDouble();
}
}
/**
* v = k * v
*
* The components of the vector are multiplied
* by k.
*
* @param v an array of doubles.
* @param k a scalar.
*/
public void mul(double[] v, double k) {
for (int i = 0; i < v.length; i++) {
v[i] *= k;
}
}
/**
* dst = src
* Copy a vector.
*
* @param dst an array of doubles
* @param src an array of doubles
*/
public void copy(double[] dst, double[] src) {
System.arraycopy(src, 0, dst, 0, src.length);
}
/**
* v = U(0, 0.1)
*
* @param v an array of doubles
*/
public void randomise(double[] v) {
randomise(v, 0.1);
}
/**
* v = U(-1, 1) * maxValue
*
* Randomise each component of a vector to
* [-maxValue, maxValue].
* thread-safety depends on Random.nextDouble().
*
* @param v an array of doubles
* @param maxValue the max value
*/
public void randomise(double[] v, double maxValue) {
for (int i = 0; i < v.length; i++) {
v[i] = (2 * rand.nextDouble() - 1) * maxValue;
}
}
/**
* For each components, reset their value to maxValue if
* their absolute value exceeds it.
*
* @param v an array of doubles
* @param maxValue if -1 this function does nothing
*/
public void clampComponents(double[] v, double maxValue) {
if (maxValue != -1) {
for (int i = 0; i < v.length; i++) {
if (v[i] > maxValue) v[i] = maxValue;
if (v[i] < -maxValue) v[i] = -maxValue;
}
}
}
/**
* Take the dot product of two vectors.
* @param v1 The first vector.
* @param v2 The second vector.
* @return The dot product.
*/
public double dotProduct(double[] v1, double[] v2) {
double d = 0;
for(int i=0;i<v1.length;i++) {
d+=v1[i]*v2[i];
}
return Math.sqrt(d);
}
}