/*
    * 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
    *
    *      https://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.
   */
  
  /*
   * This is not the original file distributed by the Apache Software Foundation
   * It has been modified by the Hipparchus project
   */
  
  package org.hipparchus.linear;
  
  import org.hipparchus.exception.LocalizedCoreFormats;
  import org.hipparchus.exception.MathIllegalArgumentException;
  import org.junit.jupiter.api.Test;
  
  import static org.junit.jupiter.api.Assertions.assertEquals;
  import static org.junit.jupiter.api.Assertions.assertThrows;
  import static org.junit.jupiter.api.Assertions.assertTrue;
  import static org.junit.jupiter.api.Assertions.fail;
  
  class CholeskyDecompositionTest {
  
      private double[][] testData = new double[][] {
              {  1,  2,   4,   7,  11 },
              {  2, 13,  23,  38,  58 },
              {  4, 23,  77, 122, 182 },
              {  7, 38, 122, 294, 430 },
              { 11, 58, 182, 430, 855 }
      };
  
      /** test dimensions */
      @Test
      void testDimensions() {
          CholeskyDecomposition llt =
              new CholeskyDecomposition(MatrixUtils.createRealMatrix(testData));
          assertEquals(testData.length, llt.getL().getRowDimension());
          assertEquals(testData.length, llt.getL().getColumnDimension());
          assertEquals(testData.length, llt.getLT().getRowDimension());
          assertEquals(testData.length, llt.getLT().getColumnDimension());
      }
  
      /** test non-square matrix */
      @Test
      void testNonSquare() {
          assertThrows(MathIllegalArgumentException.class, () -> {
              new CholeskyDecomposition(MatrixUtils.createRealMatrix(new double[3][2]));
          });
      }
  
      /** test non-symmetric matrix */
      @Test
      void testNotSymmetricMatrixException() {
          assertThrows(MathIllegalArgumentException.class, () -> {
              double[][] changed = testData.clone();
              changed[0][changed[0].length - 1] += 1.0e-5;
              new CholeskyDecomposition(MatrixUtils.createRealMatrix(changed));
          });
      }
  
      /** test non positive definite matrix */
      @Test
      void testNotPositiveDefinite() {
          assertThrows(MathIllegalArgumentException.class, () -> {
              new CholeskyDecomposition(MatrixUtils.createRealMatrix(new double[][]{
                  {14, 11, 13, 15, 24},
                  {11, 34, 13, 8, 25},
                  {13, 13, 14, 15, 21},
                  {15, 8, 15, 18, 23},
                  {24, 25, 21, 23, 45}
              }));
          });
      }
  
      @Test
      void testMath274() {
          try {
              new CholeskyDecomposition(MatrixUtils.createRealMatrix(new double[][] {
                  { 0.40434286, -0.09376327, 0.30328980, 0.04909388 },
                  {-0.09376327,  0.10400408, 0.07137959, 0.04762857 },
                  { 0.30328980,  0.07137959, 0.30458776, 0.04882449 },
                  { 0.04909388,  0.04762857, 0.04882449, 0.07543265 }
  
              }));
              fail("an exception should have been thrown");
          } catch (MathIllegalArgumentException miae) {
              assertEquals(LocalizedCoreFormats.NOT_POSITIVE_DEFINITE_MATRIX,
                                 miae.getSpecifier());
         }
     }
 
     @Test
     void testDecomposer() {
         new CholeskyDecomposer(1.0e-15, -0.2).
         decompose(MatrixUtils.createRealMatrix(new double[][] {
             { 0.40434286, -0.09376327, 0.30328980, 0.04909388 },
             {-0.09376327,  0.10400408, 0.07137959, 0.04762857 },
             { 0.30328980,  0.07137959, 0.30458776, 0.04882449 },
             { 0.04909388,  0.04762857, 0.04882449, 0.07543265 }
 
         }));
     }
 
     /** test A = LLT */
     @Test
     void testAEqualLLT() {
         RealMatrix matrix = MatrixUtils.createRealMatrix(testData);
         CholeskyDecomposition llt = new CholeskyDecomposition(matrix);
         RealMatrix l  = llt.getL();
         RealMatrix lt = llt.getLT();
         double norm = l.multiply(lt).subtract(matrix).getNorm1();
         assertEquals(0, norm, 1.0e-15);
         assertEquals(matrix.getRowDimension(),    llt.getSolver().getRowDimension());
         assertEquals(matrix.getColumnDimension(), llt.getSolver().getColumnDimension());
     }
 
     /** test that L is lower triangular */
     @Test
     void testLLowerTriangular() {
         RealMatrix matrix = MatrixUtils.createRealMatrix(testData);
         RealMatrix l = new CholeskyDecomposition(matrix).getL();
         for (int i = 0; i < l.getRowDimension(); i++) {
             for (int j = i + 1; j < l.getColumnDimension(); j++) {
                 assertEquals(0.0, l.getEntry(i, j), 0.0);
             }
         }
     }
 
     /** test that LT is transpose of L */
     @Test
     void testLTTransposed() {
         RealMatrix matrix = MatrixUtils.createRealMatrix(testData);
         CholeskyDecomposition llt = new CholeskyDecomposition(matrix);
         RealMatrix l  = llt.getL();
         RealMatrix lt = llt.getLT();
         double norm = l.subtract(lt.transpose()).getNorm1();
         assertEquals(0, norm, 1.0e-15);
     }
 
     /** test matrices values */
     @Test
     void testMatricesValues() {
         RealMatrix lRef = MatrixUtils.createRealMatrix(new double[][] {
                 {  1,  0,  0,  0,  0 },
                 {  2,  3,  0,  0,  0 },
                 {  4,  5,  6,  0,  0 },
                 {  7,  8,  9, 10,  0 },
                 { 11, 12, 13, 14, 15 }
         });
        CholeskyDecomposition llt =
             new CholeskyDecomposition(MatrixUtils.createRealMatrix(testData));
 
         // check values against known references
         RealMatrix l = llt.getL();
         assertEquals(0, l.subtract(lRef).getNorm1(), 1.0e-13);
         RealMatrix lt = llt.getLT();
         assertEquals(0, lt.subtract(lRef.transpose()).getNorm1(), 1.0e-13);
 
         // check the same cached instance is returned the second time
         assertTrue(l  == llt.getL());
         assertTrue(lt == llt.getLT());
     }
 }