/* nag_lapacklin_dptsv (f07jac) Example Program.
 *
 * Copyright 2024 Numerical Algorithms Group.
 *
 * Mark 30.2, 2024.
 */

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

int main(void) {

  /* Scalars */
  Integer exit_status = 0, i, j, n, nrhs, pdb;
  Nag_OrderType order;

  /* Arrays */
  double *b = 0, *d = 0, *e = 0;

  /* Nag Types */
  NagError fail;

#ifdef NAG_COLUMN_MAJOR
#define B(I, J) b[(J - 1) * pdb + I - 1]
  order = Nag_ColMajor;
#else
#define B(I, J) b[(I - 1) * pdb + J - 1]
  order = Nag_RowMajor;
#endif
  INIT_FAIL(fail);

  printf("nag_lapacklin_dptsv (f07jac) Example Program Results\n\n");

  /* Skip heading in data file */
  scanf("%*[^\n]");
  scanf("%" NAG_IFMT "%" NAG_IFMT "%*[^\n]", &n, &nrhs);
  if (n < 0 || nrhs < 0) {
    printf("Invalid n or nrhs\n");
    exit_status = 1;
    goto END;
  }
  /* Allocate memory */
  if (!(b = NAG_ALLOC(n * nrhs, double)) || !(d = NAG_ALLOC(n, double)) ||
      !(e = NAG_ALLOC(n - 1, double))) {
    printf("Allocation failure\n");
    exit_status = -1;
    goto END;
  }
#ifdef NAG_COLUMN_MAJOR
  pdb = n;
#else
  pdb = nrhs;
#endif

  /* Read the lower bidiagonal part of the tridiagonal matrix A and the
   * right hand side b from data file.
   */
  for (i = 0; i < n; ++i)
    scanf("%lf", &d[i]);
  scanf("%*[^\n]");
  for (i = 0; i < n - 1; ++i)
    scanf("%lf", &e[i]);
  scanf("%*[^\n]");

  for (i = 1; i <= n; ++i)
    for (j = 1; j <= nrhs; ++j)
      scanf("%lf", &B(i, j));
  scanf("%*[^\n]");

  /* Solve the equations Ax = b for x using nag_lapacklin_dptsv (f07jac). */
  nag_lapacklin_dptsv(order, n, nrhs, d, e, b, pdb, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_lapacklin_dptsv (f07jac).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }

  /* Print solution */
  printf("Solution\n");
  for (i = 1; i <= n; ++i) {
    for (j = 1; j <= nrhs; ++j)
      printf("%11.4f%s", B(i, j), j % 7 == 0 ? "\n" : " ");
    printf("\n");
  }

  /* Print details of factorization */
  printf("\nDiagonal elements of the diagonal matrix D\n");
  for (i = 0; i < n; ++i)
    printf("%11.4f%s", d[i], i % 7 == 6 ? "\n" : " ");

  printf("\n\nSubdiagonal elements of the Cholesky factor L\n");
  for (i = 0; i < n - 1; ++i)
    printf("%11.4f%s", e[i], i % 7 == 6 ? "\n" : " ");
  printf("\n");
END:
  NAG_FREE(b);
  NAG_FREE(d);
  NAG_FREE(e);

  return exit_status;
}