NAG Library Manual, Mark 28.3
Interfaces:  FL   CL   CPP   AD 

NAG CL Interface Introduction
Example description
/* nag_matop_real_tri_matmul_inplace (f01dgc) Example Program.
 *
 * Copyright 2022 Numerical Algorithms Group.
 *
 * Mark 28.3, 2022.
 */

#include <nag.h>
#include <stdio.h>

int main(void) {

  /* Scalars */
  double alpha;
  Integer exit_status, i, j, n, pda, pdb;

  /* Arrays */
  double *a = 0, *b = 0;
  char nag_enum_arg[40];

  /* Nag Types */
  Nag_OrderType order = Nag_ColMajor;
  NagError fail;
  Nag_SideType side;
  Nag_UploType uplo;
  Nag_TransType transa;
  Nag_MatrixType matrix;
#define A(I, J) a[J * pda + I]
#define B(I, J) b[J * pdb + I]

  exit_status = 0;
  INIT_FAIL(fail);

  printf("nag_matop_real_tri_matmul_inplace (f01dgc) Example Program Results");
  printf("\n\n");

  /* Skip heading in data file. */
  scanf("%*[^\n] ");

  /* Read the problem dimensions */
  scanf("%" NAG_IFMT "%*[^\n] ", &n);

  pda = n;
  pdb = n;

  /* Read side */
  scanf(" %39s%*[^\n] ", nag_enum_arg);
  /* nag_enum_name_to_value (x04nac).
   * Converts NAG enum member name to value
   */
  side = (Nag_SideType)nag_enum_name_to_value(nag_enum_arg);

  /* Read uplo */
  scanf(" %39s%*[^\n] ", nag_enum_arg);
  /* nag_enum_name_to_value (x04nac), see above. */
  uplo = (Nag_UploType)nag_enum_name_to_value(nag_enum_arg);

  /* Read transa */
  scanf(" %39s%*[^\n] ", nag_enum_arg);
  /* nag_enum_name_to_value (x04nac), see above. */
  transa = (Nag_TransType)nag_enum_name_to_value(nag_enum_arg);

  /* Read scalar parameters */
  scanf("%lf%*[^\n] ", &alpha);

  if (n > 0) {
    /* Allocate memory */
    if (!(a = NAG_ALLOC(n * n, double)) || !(b = NAG_ALLOC(n * n, double))) {
      printf("Allocation failure\n");
      exit_status = -1;
      goto END;
    }
  } else {
    printf("Invalid n\n");
    exit_status = 1;
    return exit_status;
  }

  /* Read A from data file */
  if (uplo == Nag_Upper) {
    matrix = Nag_UpperMatrix;
    for (i = 0; i < n; i++) {
      for (j = i; j < n; j++) {
        scanf("%lf", &A(i, j));
      }
    }
  } else {
    matrix = Nag_LowerMatrix;
    for (i = 0; i < n; i++) {
      for (j = 0; j <= i; j++) {
        scanf("%lf", &A(i, j));
      }
    }
  }
  scanf("%*[^\n] ");

  /* Read B from data file */
  if (uplo == Nag_Upper) { /* B is upper triangular */
    for (i = 0; i < n; i++) {
      for (j = i; j < n; j++) {
        scanf("%lf", &B(i, j));
      }
    }
  } else { /* B is lower triangular */
    for (i = 0; i < n; i++) {
      for (j = 0; j <= i; j++) {
        scanf("%lf", &B(i, j));
      }
    }
  }
  scanf("%*[^\n] ");

  /* nag_matop_real_tri_matmul_inplace (f01dgc).
   *
   */
  nag_matop_real_tri_matmul_inplace(side, uplo, transa, n, alpha, a, pda, b,
                                    pdb, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_matop_real_tri_matmul_inplace (f01dgc).\n%s\n",
           fail.message);
    exit_status = 2;
    goto END;
  }

  /* Print the updated matrix B */
  /* nag_file_print_matrix_real_gen (x04cac).
   * Print real general matrix (easy-to-use)
   */
  fflush(stdout);

  if (transa == Nag_Trans)
    matrix = Nag_GeneralMatrix;

  nag_file_print_matrix_real_gen(order, matrix, Nag_NonUnitDiag, n, n, b, pdb,
                                 "Solution matrix B", 0, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_file_print_matrix_real_gen (x04cac).\n%s\n",
           fail.message);
    exit_status = 3;
    goto END;
  }

END:
  NAG_FREE(a);
  NAG_FREE(b);

  return exit_status;
}