NAG Library Manual, Mark 29.3
Interfaces:  FL   CL   CPP   AD 

NAG CL Interface Introduction
Example description
/* nag_matop_real_tri_matmul (f01dfc) Example Program.
 *
 * Copyright 2023 Numerical Algorithms Group.
 *
 * Mark 29.3, 2023.
 */

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

int main(void) {

  /* Scalars */
  double alpha, beta;
  Integer exit_status, i, j, n, pda, pdb, pdc, lu, lta, ltb;

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

  /* Nag Types */
  Nag_OrderType order = Nag_ColMajor;
  NagError fail;
  Nag_UploType uplo;
  Nag_TransType transa, transb;

#define A(I, J) a[J * pda + I]
#define B(I, J) b[J * pdb + I]
#define C(I, J) c[J * pdc + I]

  exit_status = 0;
  INIT_FAIL(fail);

  printf("nag_matop_real_tri_matmul (f01dfc) Example Program Results\n\n");

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

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

  pda = n;
  pdb = n;
  pdc = n;

  /* 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);
  lu = (uplo == Nag_Lower ? 0 : 1);

  /* 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);
  lta = (transa == Nag_Trans ? 0 : 1);

  /* Read transb */
  scanf("%39s%*[^\n] ", nag_enum_arg);
  /* nag_enum_name_to_value (x04nac), see above. */
  transb = (Nag_TransType)nag_enum_name_to_value(nag_enum_arg);
  ltb = (transb == Nag_Trans ? 0 : 1);

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

  if (n > 0) {
    /* Allocate memory */
    if (!(a = NAG_ALLOC(n * n, double)) || !(b = NAG_ALLOC(n * n, double)) ||
        !(c = 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 (lu == lta) {
    /* A is upper triangular */
    for (i = 0; i < n; i++) {
      for (j = i; j < n; j++) {
        scanf("%lf", &A(i, j));
      }
    }
  } else {
    /* A is lower triangular */
    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 (lu == ltb) {
    /* 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] ");

  /* Read C from data file */
  for (i = 0; i < n; i++) {
    for (j = 0; j < n; j++) {
      scanf("%lf", &C(i, j));
    }
  }
  scanf("%*[^\n] ");

  /* nag_matop_real_tri_matmul (f01dfc).
   *
   */
  nag_matop_real_tri_matmul(uplo, transa, transb, n, alpha, a, pda, b, pdb,
                            beta, c, pdc, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_matop_real_tri_matmul (f01dfc).\n%s\n",
           fail.message);
    exit_status = 1;
    goto END;
  }

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

  nag_gen_real_mat_print(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n, n, c,
                         pdc, "Solution matrix C", 0, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_gen_real_mat_print (x04cac).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }

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

  return exit_status;
}