/*
	This example shows the amount of time a process will
	take to run when it causes Overflow floating point exceptions
	(fpes).

	The inner loop, loop1, will cause MAX Overflow fpes. The outer
	loop will loop two times. The first time through the outer loop,
	Overflow fpes will not be enabled ( the FPU is handling the
	Overflow fpe ).
	The second time through the outer loop, Overflow fpes will be
	enabled ( the process is handling the Overflow fpe ).

	Notice the time differences spent in user and kernel mode
	between the two loop iterations.

	One should avoid raising fpes in general, specifically
	signaling fpes which cause software to handle the fpe.

	Here are the results from a test ran on a 100 MHZ IP22
	MIPS RISC Processor:

		cc test4.c -o test4 -lfpe
		su
		./test4

		res = inf
 		time spent in system in micro-seconds = 49
 		time spent in user in micro-seconds   = 1517

 		res = 20.000000
 		time spent in system in micro-seconds = 2766800
 		time spent in user in micro-seconds   = 563537
*/

#include <sigfpe.h>
#include <stdio.h>
#include <limits.h>
#include <math.h>
#include <sys/resource.h>
#include <sys/time.h>
#include <sys/schedctl.h>
#include <sys/lock.h>

#define MAX 10000	/* Max loop iterations      */
#define MSPS 1000000	/* Micro Seconds Per Second */

void handler_rout(exception, ret_val)
int exception[5];
float ret_val[2];
{
        switch(exception[_EXCEPTION_TYPE]) {
                case _OVERFL :
                        ret_val[0] = 20.0;
                        break;
        }
}

main()
{
        register float res,max,ten;
        register int i,q,dts,dtu;
	struct rusage r1,r2;

        if ( plock ( PROCLOCK ) != 0 )
            perror ( "Failed plock" ) ;
        if (schedctl(NDPRI, 0, NDPHIMAX) != 0)
            perror( "Failed schedctl" ) ;

        max = FLT_MAX;
        ten = 10.0;

	for(q=0;q<2;q++) {

	  if ((getrusage(0,&r1)) == -1) {
		  perror("getrusage");
		  exit(-1);
	  }
	  /* Let's generate some overflows */
	  i = 0;
          loop1:
                res = max*ten;
                if (i++ < MAX) goto loop1;

          if ((getrusage(0,&r2)) == -1) {
                  perror("getrusage");
                  exit(-1);
          }

	  dtu =((r2.ru_utime.tv_sec*MSPS) + r2.ru_utime.tv_usec) -
	       ((r1.ru_utime.tv_sec*MSPS) + r1.ru_utime.tv_usec);
	  dts =((r2.ru_stime.tv_sec*MSPS) + r2.ru_stime.tv_usec) -
	       ((r1.ru_stime.tv_sec*MSPS) + r1.ru_stime.tv_usec);

	  printf(" res = %f\n",res);
	  printf(" time spent in system in micro-seconds = %d\n",dts);
	  printf(" time spent in user in micro-seconds   = %d\n\n",dtu);

          /* Establish handler_rout() to be the module to handle SIGFPEs  */
          sigfpe_[_OVERFL].repls = _USER_DETERMINED;
          handle_sigfpes (_ON, _EN_OVERFL , (void*)handler_rout, 0, 0);
	}
	exit(1);
}