/* nag_linsys_real_posdef_vband_solve (f04mcc) Example Program.
 *
 * Copyright 2024 Numerical Algorithms Group.
 *
 * Mark 30.1, 2024.
 */

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

#define B(I, J) b[(I)*tdb + J]
#define X(I, J) x[(I)*tdx + J]

int main(void) {
  Integer exit_status = 0, i, k, k1, k2, lal, n, nrhs, *row = 0, tdb, tdx;
  Nag_SolveSystem select;
  double *a = 0, *al = 0, *b = 0, *d = 0, *x = 0;
  NagError fail;

  INIT_FAIL(fail);

  printf(
      "nag_linsys_real_posdef_vband_solve (f04mcc) Example Program Results\n");
  /* Skip heading in data file */
  scanf("%*[^\n]");
  scanf("%" NAG_IFMT "", &n);
  if (n >= 1) {
    if (!(row = NAG_ALLOC(n, Integer))) {
      printf("Allocation failure\n");
      exit_status = -1;
      goto END;
    }
  } else {
    printf("Invalid n.\n");
    exit_status = 1;
    return exit_status;
  }

  lal = 0;
  for (i = 0; i < n; ++i) {
    scanf("%" NAG_IFMT "", &row[i]);
    lal += row[i];
  }
  if (!(a = NAG_ALLOC(lal, double)) || !(al = NAG_ALLOC(lal, double))) {
    printf("Allocation failure\n");
    exit_status = -1;
    goto END;
  }
  k2 = 0;
  for (i = 0; i < n; ++i) {
    k1 = k2;
    k2 = k2 + row[i];
    for (k = k1; k < k2; ++k)
      scanf("%lf", &a[k]);
  }
  scanf("%" NAG_IFMT "", &nrhs);
  if (nrhs >= 1) {
    if (!(b = NAG_ALLOC(n * nrhs, double)) || !(d = NAG_ALLOC(n, double)) ||
        !(x = NAG_ALLOC(n * nrhs, double))) {
      printf("Allocation failure\n");
      exit_status = -1;
      goto END;
    }
    tdb = nrhs;
    tdx = nrhs;
  } else {
    printf("Invalid nrhs.\n");
    exit_status = 1;
    return exit_status;
  }
  for (i = 0; i < n; ++i)
    for (k = 0; k < nrhs; ++k)
      scanf("%lf", &B(i, k));
  /* nag_matop_real_vband_posdef_fac (f01mcc).
   * LDL^T factorization of real symmetric positive-definite
   * variable-bandwidth (skyline) matrix
   */
  nag_matop_real_vband_posdef_fac(n, a, lal, row, al, d, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_matop_real_vband_posdef_fac (f01mcc).\n%s\n",
           fail.message);
    exit_status = 1;
    goto END;
  }
  select = Nag_LDLTX;
  /* nag_linsys_real_posdef_vband_solve (f04mcc).
   * Approximate solution of real symmetric positive-definite
   * variable-bandwidth simultaneous linear equations
   * (coefficient matrix already factorized by
   * nag_matop_real_vband_posdef_fac (f01mcc))
   */
  nag_linsys_real_posdef_vband_solve(select, n, nrhs, al, lal, d, row, b, tdb,
                                     x, tdx, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_linsys_real_posdef_vband_solve (f04mcc).\n%s\n",
           fail.message);
    exit_status = 1;
    goto END;
  }
  printf("\n Solution\n");
  for (i = 0; i < n; ++i) {
    for (k = 0; k < nrhs; ++k)
      printf("%9.3f", X(i, k));
    printf("\n");
  }
END:
  NAG_FREE(row);
  NAG_FREE(b);
  NAG_FREE(d);
  NAG_FREE(x);
  NAG_FREE(a);
  NAG_FREE(al);
  return exit_status;
}