/* nag_1d_quad_brkpts (d01alc) Example Program.
 *
 * Copyright 1991 Numerical Algorithms Group.
 *
 * Mark 2, 1991.
 * Mark 6 revised, 2000.
 * Mark 7 revised, 2001.
 */

#include <nag.h>
#include <stdio.h>
#include <nag_stdlib.h>
#include <math.h>
#include <nagd01.h>

#ifdef __cplusplus
extern "C" {
#endif
static double NAG_CALL f(double x);
#ifdef __cplusplus
}
#endif

int main(void)
{
  Integer          exit_status = 0;
  double           a, b;
  double           epsabs, abserr, epsrel, brkpts[1], result;
  Integer          nbrkpts;
  Nag_QuadProgress qp;
  Integer          max_num_subint;
  NagError         fail;

  INIT_FAIL(fail);

  printf("nag_1d_quad_brkpts (d01alc) Example Program Results\n");
  nbrkpts = 1;
  epsabs = 0.0;
  epsrel = 0.001;
  a = 0.0;
  b = 1.0;
  max_num_subint = 200;
  brkpts[0] = 1.0/7.0;
  /* nag_1d_quad_brkpts (d01alc).
   * One-dimensional adaptive quadrature, allowing for
   * singularities at specified points
   */
  nag_1d_quad_brkpts(f, a, b, nbrkpts, brkpts, epsabs, epsrel, max_num_subint,
                     &result, &abserr, &qp, &fail);
  printf("a      - lower limit of integration  = %9.4f\n", a);
  printf("b      - upper limit of integration  = %9.4f\n", b);
  printf("epsabs - absolute accuracy requested = %11.2e\n", epsabs);
  printf("epsrel - relative accuracy requested = %11.2e\n\n", epsrel);
  printf("brkpts[0] - given break-point           = %9.4f\n",
          brkpts[0]);

  if (fail.code != NE_NOERROR)
    printf("Error from nag_1d_quad_brkpts (d01alc) %s\n", fail.message);

  if (fail.code != NE_INT_ARG_LT && fail.code != NE_2_INT_ARG_LE &&
      fail.code != NE_ALLOC_FAIL && fail.code != NE_NO_LICENCE)
    {
      /* Free memory used by qp pointers */
      NAG_FREE(qp.sub_int_beg_pts);
      NAG_FREE(qp.sub_int_end_pts);
      NAG_FREE(qp.sub_int_result);
      NAG_FREE(qp.sub_int_error);
    }
  if (fail.code != NE_INT_ARG_LT && fail.code != NE_2_INT_ARG_LE
     && fail.code != NE_QUAD_BRKPTS_INVAL && fail.code != NE_ALLOC_FAIL &&
      fail.code != NE_NO_LICENCE)
    {
      printf("result - approximation to the integral  = %10.5f\n",
              result);
      printf("abserr - estimate of the absolute error = %11.2e\n",
              abserr);
      printf("qp.fun_count  - number of function evaluations = %4ld\n",
              qp.fun_count);
      printf("qp.num_subint - number of subintervals used    = %4ld\n",
              qp.num_subint);
    }
  else
    {
      exit_status = 1;
      goto END;
    }

 END:
  return exit_status;
}

static double NAG_CALL f(double x)
{
  double a;
  a = FABS(x-1.0/7.0);
  return (a != 0.0)?pow(a, -0.5):0.0;
}