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

NAG CL Interface Introduction
Example description
/* nag_blast_dsf_norm (f16rkc) Example Program.
 *
 * Copyright 2022 Numerical Algorithms Group.
 *
 * Mark 28.3, 2022.
 */

#include <nag.h>

int main(void) {
  /* Scalars */
  Integer exit_status = 0;
  double r_fro, r_inf, r_max, r_one;
  Integer i, j, n, pda;
  /* Arrays */
  double *a = 0, *ar = 0;
  char nag_enum_arg[40];
  /* Nag Types */
  Nag_OrderType order;
  Nag_RFP_Store transr;
  Nag_UploType uplo;
  NagError fail;

#ifdef NAG_COLUMN_MAJOR
#define A(I, J) a[(J - 1) * pda + I - 1]
  order = Nag_ColMajor;
#else
#define A(I, J) a[(I - 1) * pda + J - 1]
  order = Nag_RowMajor;
#endif

  INIT_FAIL(fail);

  printf("nag_blast_dsf_norm (f16rkc) Example Program Results\n");
  /* Skip heading in data file */
  scanf("%*[^\n] ");
  scanf("%" NAG_IFMT "%*[^\n] ", &n);
  pda = n;
  if (!(a = NAG_ALLOC(pda * n, double)) ||
      !(ar = NAG_ALLOC((n * (n + 1)) / 2, double))) {
    printf("Allocation failure\n");
    exit_status = -1;
    goto END;
  }
  /* Nag_RFP_Store */
  scanf("%39s ", nag_enum_arg);
  transr = (Nag_RFP_Store)nag_enum_name_to_value(nag_enum_arg);
  /* Nag_UploType */
  scanf("%39s  %*[^\n] ", nag_enum_arg);
  uplo = (Nag_UploType)nag_enum_name_to_value(nag_enum_arg);
  /* Read upper or lower triangle of matrix A from data file. */
  if (uplo == Nag_Lower) {
    for (i = 1; i <= n; i++) {
      for (j = 1; j <= i; j++) {
        scanf("%lf", &A(i, j));
      }
    }
  } else {
    for (i = 1; i <= n; i++) {
      for (j = i; j <= n; j++) {
        scanf("%lf", &A(i, j));
      }
    }
  }
  /* Convert real symmetric matrix A from full to rectangular full packed
   * storage format (stored in ar) using nag_matop_dtrttf (f01vec).
   */
  nag_matop_dtrttf(order, transr, uplo, n, a, pda, ar, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_matop_dtrttf (f01vec).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }

  printf("\nNorms of symmetric matrix stored in RFP format in ar:\n\n");

  /* Get, in turn, the 1-norm, infinity norm, Frobenius norm, and
   * largest absolute element of the real symmetric matrix A stored
   * in rectangular full packed format in ar using nag_blast_dsf_norm (f16rkc).
   */
  nag_blast_dsf_norm(order, Nag_OneNorm, transr, uplo, n, ar, &r_one, &fail);

  if (fail.code == NE_NOERROR) {
    printf("One norm           = %9.4f\n", r_one);
    nag_blast_dsf_norm(order, Nag_InfNorm, transr, uplo, n, ar, &r_inf, &fail);
  }
  if (fail.code == NE_NOERROR) {
    printf("Infinity norm      = %9.4f\n", r_inf);
    nag_blast_dsf_norm(order, Nag_FrobeniusNorm, transr, uplo, n, ar, &r_fro,
                       &fail);
  }
  if (fail.code == NE_NOERROR) {
    printf("Frobenius norm     = %9.4f\n", r_fro);
    nag_blast_dsf_norm(order, Nag_MaxNorm, transr, uplo, n, ar, &r_max, &fail);
  }
  if (fail.code == NE_NOERROR) {
    printf("Maximum norm       = %9.4f\n", r_max);
  } else {
    printf("Error from nag_blast_dsf_norm (f16rkc).\n%s\n", fail.message);
    exit_status = 1;
  }

END:
  NAG_FREE(a);
  NAG_FREE(ar);
  return exit_status;
}