1  /* ----------------------------------------------------------------------
  2   * Project:      CMSIS DSP Library
  3   * Title:        arm_mat_solve_upper_triangular_f64.c
  4   * Description:  Solve linear system UT X = A with UT upper triangular matrix
  5   *
  6   * $Date:        23 April 2021
  7   * $Revision:    V1.9.0
  8   *
  9   * Target Processor: Cortex-M and Cortex-A cores
 10   * -------------------------------------------------------------------- */
 11  /*
 12   * Copyright (C) 2010-2021 ARM Limited or its affiliates. All rights reserved.
 13   *
 14   * SPDX-License-Identifier: Apache-2.0
 15   *
 16   * Licensed under the Apache License, Version 2.0 (the License); you may
 17   * not use this file except in compliance with the License.
 18   * You may obtain a copy of the License at
 19   *
 20   * www.apache.org/licenses/LICENSE-2.0
 21   *
 22   * Unless required by applicable law or agreed to in writing, software
 23   * distributed under the License is distributed on an AS IS BASIS, WITHOUT
 24   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 25   * See the License for the specific language governing permissions and
 26   * limitations under the License.
 27   */
 28  
 29  #include "dsp/matrix_functions.h"
 30  
 31  
 32  /**
 33    @ingroup groupMatrix
 34   */
 35  
 36  
 37  /**
 38    @addtogroup MatrixInv
 39    @{
 40   */
 41  
 42  /**
 43     * @brief Solve UT . X = A where UT is an upper triangular matrix
 44     * @param[in]  ut  The upper triangular matrix
 45     * @param[in]  a  The matrix a
 46     * @param[out] dst The solution X of UT . X = A
 47     * @return The function returns ARM_MATH_SINGULAR, if the system can't be solved.
 48    */
 49    arm_status arm_mat_solve_upper_triangular_f64(
 50    const arm_matrix_instance_f64 * ut,
 51    const arm_matrix_instance_f64 * a,
 52    arm_matrix_instance_f64 * dst)
 53    {
 54  arm_status status;                             /* status of matrix inverse */
 55  
 56  
 57  #ifdef ARM_MATH_MATRIX_CHECK
 58  
 59    /* Check for matrix mismatch condition */
 60    if ((ut->numRows != ut->numCols) ||
 61        (ut->numRows != a->numRows)   )
 62    {
 63      /* Set status as ARM_MATH_SIZE_MISMATCH */
 64      status = ARM_MATH_SIZE_MISMATCH;
 65    }
 66    else
 67  
 68  #endif /* #ifdef ARM_MATH_MATRIX_CHECK */
 69  
 70    {
 71  
 72      int i,j,k,n,cols;
 73  
 74      float64_t *pX = dst->pData;
 75      float64_t *pUT = ut->pData;
 76      float64_t *pA = a->pData;
 77  
 78      float64_t *ut_row;
 79      float64_t *a_col;
 80  
 81      n = dst->numRows;
 82      cols = dst->numCols;
 83  
 84      for(j=0; j < cols; j ++)
 85      {
 86         a_col = &pA[j];
 87  
 88         for(i=n-1; i >= 0 ; i--)
 89         {
 90              float64_t tmp=a_col[i * cols];
 91  
 92              ut_row = &pUT[n*i];
 93  
 94              for(k=n-1; k > i; k--)
 95              {
 96                  tmp -= ut_row[k] * pX[cols*k+j];
 97              }
 98  
 99              if (ut_row[i]==0.0)
100              {
101                return(ARM_MATH_SINGULAR);
102              }
103              tmp = tmp / ut_row[i];
104              pX[i*cols+j] = tmp;
105         }
106  
107      }
108      status = ARM_MATH_SUCCESS;
109  
110    }
111  
112    
113    /* Return to application */
114    return (status);
115  }
116  
117  
118  /**
119    @} end of MatrixInv group
120   */