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* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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,
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* See the License for the specific language governing permissions and
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package org.apache.ignite.examples.ml.math.decompositions;
import org.apache.ignite.ml.math.Matrix;
import org.apache.ignite.ml.math.Tracer;
import org.apache.ignite.ml.math.decompositions.CholeskyDecomposition;
import org.apache.ignite.ml.math.impls.matrix.DenseLocalOnHeapMatrix;
/**
* Example of using {@link CholeskyDecomposition}.
*/
public class CholeskyDecompositionExample {
/**
* Executes example.
*
* @param args Command line arguments, none required.
*/
public static void main(String[] args) {
System.out.println(">>> Cholesky decomposition example started.");
// Let's compute a Cholesky decomposition of Hermitian matrix m:
// m = l l^{*}, where
// l is a lower triangular matrix
// l^{*} is its conjugate transpose
DenseLocalOnHeapMatrix m = new DenseLocalOnHeapMatrix(new double[][] {
{2.0d, -1.0d, 0.0d},
{-1.0d, 2.0d, -1.0d},
{0.0d, -1.0d, 2.0d}
});
System.out.println("\n>>> Matrix m for decomposition: ");
Tracer.showAscii(m);
// This decomposition is useful when dealing with systems of linear equations of the form
// m x = b where m is a Hermitian matrix.
// For such systems Cholesky decomposition provides
// more effective method of solving compared to LU decomposition.
// Suppose we want to solve system
// m x = b for various bs. Then after we computed Cholesky decomposition, we can feed various bs
// as a matrix of the form
// (b1, b2, ..., bm)
// to the method Cholesky::solve which returns solutions in the form
// (sol1, sol2, ..., solm)
CholeskyDecomposition dec = new CholeskyDecomposition(m);
System.out.println("\n>>> Made decomposition m = l * l^{*}.");
System.out.println(">>> Matrix l is ");
Tracer.showAscii(dec.getL());
System.out.println(">>> Matrix l^{*} is ");
Tracer.showAscii(dec.getLT());
Matrix bs = new DenseLocalOnHeapMatrix(new double[][] {
{4.0, -6.0, 7.0},
{1.0, 1.0, 1.0}
}).transpose();
System.out.println("\n>>> Solving systems of linear equations of the form m x = b for various bs represented by columns of matrix");
Tracer.showAscii(bs);
Matrix sol = dec.solve(bs);
System.out.println("\n>>> List of solutions: ");
for (int i = 0; i < sol.columnSize(); i++)
Tracer.showAscii(sol.viewColumn(i));
System.out.println("\n>>> Cholesky decomposition example completed.");
}
}