/* nag_sparse_sym_chol_sol (f11jcc) Example Program.
 *
 * Copyright 1998 Numerical Algorithms Group.
 *
 * Mark 5, 1998.
 *
 */

#include <nag.h>
#include <stdio.h>
#include <nag_stdlib.h>
#include <nag_string.h>
#include <nagf11.h>

int main(void)
{
  double dtol;
  double *a=0, *b=0;
  double *x=0;
  double rnorm, dscale;
  double tol;

  Integer *icol=0;
  Integer *ipiv=0, nnzc, *irow=0, *istr=0;
  Integer i;
  Integer n;
  Integer lfill, npivm;
  Integer maxitn;
  Integer itn;
  Integer nnz;
  Integer num;

  Nag_SparseSym_Method method;
  Nag_SparseSym_Piv pstrat;
  Nag_SparseSym_Fact mic;
  Nag_Sparse_Comm comm;

  char char_enum[20];

  Vprintf("nag_sparse_sym_chol_sol (f11jcc) Example Program Results\n");

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

  /* Read algorithmic parameters */
  Vscanf("%ld%*[^\n]",&n);
  Vscanf("%ld%*[^\n]",&nnz);
  Vscanf("%ld%lf%*[^\n]",&lfill, &dtol);
  Vscanf("%s%*[^\n]",char_enum);
  if (!strcmp(char_enum, "CG"))
    method = Nag_SparseSym_CG;
  else if (!strcmp(char_enum, "Lanczos"))
    method = Nag_SparseSym_Lanczos;
  else
    {
      Vprintf("Unrecognised string for method enum representation.\n");
      return EXIT_FAILURE;
    }

  Vscanf("%s%lf%*[^\n]",char_enum, &dscale);
  if (!strcmp(char_enum, "ModFact"))
    mic = Nag_SparseSym_ModFact;
  else if (!strcmp(char_enum, "UnModFact"))
    mic = Nag_SparseSym_UnModFact;
  else
    {
      Vprintf("Unrecognised string for mic enum representation.\n");
      return EXIT_FAILURE;
    }

  Vscanf("%s%*[^\n]",char_enum);
  if (!strcmp(char_enum, "NoPiv"))
    pstrat = Nag_SparseSym_NoPiv;
  else if (!strcmp(char_enum, "MarkPiv"))
    pstrat = Nag_SparseSym_MarkPiv;
  else if (!strcmp(char_enum, "UserPiv"))
    pstrat = Nag_SparseSym_UserPiv;
  else
    {
      Vprintf("Unrecognised string for pstrat enum representation.\n");
      return EXIT_FAILURE;
    }

  Vscanf("%lf%ld%*[^\n]",&tol, &maxitn);

  /* Read the matrix a */

  num = 2 * nnz;
  irow = NAG_ALLOC(num,Integer);
  icol = NAG_ALLOC(num,Integer);
  a = NAG_ALLOC(num,double);
  b = NAG_ALLOC(n,double);
  x = NAG_ALLOC(n,double);
  istr = NAG_ALLOC(n+1,Integer);
  ipiv = NAG_ALLOC(num,Integer);

  if (!irow || !icol || !a || !x || !istr ||!ipiv)
    {
      Vprintf("Allocation failure\n");
      return EXIT_FAILURE;
    }

  for (i = 1; i <= nnz; ++i)
    Vscanf("%lf%ld%ld%*[^\n]",&a[i-1], &irow[i-1], &icol[i-1]);

  /* Read right-hand side vector b and initial approximate solution x */

  for (i = 1; i <= n; ++i)
    Vscanf("%lf",&b[i-1]);
  Vscanf(" %*[^\n]");

  for (i = 1; i <= n; ++i)
    Vscanf("%lf",&x[i-1]);
  Vscanf("%*[^\n]");

  /* Calculate incomplete Cholesky factorization */

  /* nag_sparse_sym_chol_fac (f11jac).
   * Incomplete Cholesky factorization (symmetric)
   */
  nag_sparse_sym_chol_fac(n, nnz, &a, &num, &irow, &icol, lfill, dtol, mic,
                          dscale, pstrat, ipiv, istr, &nnzc, &npivm, &comm,
                          NAGERR_DEFAULT);

  /* Solve Ax = b */

  /* nag_sparse_sym_chol_sol (f11jcc).
   * Solver with incomplete Cholesky preconditioning
   * (symmetric)
   */
  nag_sparse_sym_chol_sol(method, n, nnz, a, num, irow, icol, ipiv, istr, b,
                          tol, maxitn, x, &rnorm, &itn, &comm, NAGERR_DEFAULT);

  Vprintf(" %s%10ld%s\n","Converged in",itn," iterations");
  Vprintf(" %s%16.3e\n","Final residual norm =",rnorm);

  /* Output x */

  for (i = 1; i <= n; ++i)
    Vprintf(" %16.4e\n",x[i-1]);

  NAG_FREE(irow);
  NAG_FREE(icol);
  NAG_FREE(a);
  NAG_FREE(b);
  NAG_FREE(x);
  NAG_FREE(ipiv);
  NAG_FREE(istr);
  return EXIT_SUCCESS;
}