/* nag_roots_sys_func_aa_rcomm (c05mdc) Example Program.
 *
 * Copyright 2019 Numerical Algorithms Group.
 *
 * Mark 27.0, 2019.
 */

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

int main(void)
{
  Integer  exit_status = 0, i, n = 4, irevcm = 0, m = 2, astart = 0, icount =
    0, imax = 50, exit_loop = 0;
  double   *fvec = 0, *x = 0, *rwsav = 0;
  Integer  *iwsav = 0;
  double   cndtol = 0.0, rtol, atol;
  /* Nag Types */
  NagError fail;

  INIT_FAIL(fail);

  printf("nag_roots_sys_func_aa_rcomm (c05mdc) Example Program Results\n");

  if (!(fvec = NAG_ALLOC(n, double)) ||
      !(x = NAG_ALLOC(n, double)) ||
      !(iwsav = NAG_ALLOC(14+m, Integer)) ||
      !(rwsav = NAG_ALLOC(2*m*n+m*m+m+2*n+1+MIN(m, 1)*MAX(n, 3*m), double)))
    {
      printf("Allocation failure\n");
      exit_status = -1;
      goto END;
    }

  /* The following starting values provide a rough solution. */
  x[0] = 2.0;
  x[1] = 0.5;
  x[2] = 2.0;
  x[3] = 0.5;

  /* nag_machine_precision (x02ajc).
   * The machine precision
   */
  atol = sqrt(nag_machine_precision);
  rtol = sqrt(nag_machine_precision);

  /* nag_roots_sys_func_aa_rcomm (c05mdc).
   * Solution of a system of nonlinear equations using Anderson acceleration
   * (reverse communication)
   */

  do
    {
      nag_roots_sys_func_aa_rcomm(&irevcm, n, x, fvec, atol, rtol, m,
                                    cndtol, astart, iwsav, rwsav, &fail);

      switch (irevcm)
        {
        case 1:
          if (icount == imax)
            {
              printf("Exiting after the maximum number of iterations\n\n");
              exit_loop = 1;
            }
          else
            {
              icount++;
            }
          /* x and fvec are available for printing */
          break;
        case 2:
          fvec[0] = cos(x[2]) - x[0];
          fvec[1] = sqrt(1.0 - x[3]*x[3])- x[1];
          fvec[2] = sin(x[0]) - x[2];
          fvec[3] = x[1]*x[1] - x[3];
          break;
        }
    } while (irevcm != 0 && exit_loop == 0);

      
  if (fail.code != NE_NOERROR)
    {
      printf("Error from nag_roots_sys_func_aa_rcomm (c05mdc).\n%s\n",
             fail.message);
      exit_status = 1;
      goto END;
    }

  printf("Final approximate solution after %" NAG_IFMT" iterations\n\n", icount);
  for (i = 0; i < n; i++)
    printf("%12.4f  ", x[i]);

  printf("\n");

  if (fail.code != NE_NOERROR)
    exit_status = 2;

 END:
  NAG_FREE(fvec);
  NAG_FREE(x);
  NAG_FREE(iwsav);
  NAG_FREE(rwsav);
  return exit_status;
}