/******************************************************
/*
/* consume ratio freq
/*         to cosnume cpu time at ratio and frequency.
/*         The original code was from Peter Zijlstra,
/*         the  kernal.org maintainer of the sched
/*         area of the kernel code.
/*
/* consume.c Smythies 2012.06.27
/*         More precision desired. Switch to doubles for
/*         run time parameters.
/*
/* consume.c Smythies 2012.06.23
/*         I think in frequency for this stuff, so change
/*         the run time parameter from period to frequency.
/*         Make it not optional.
/*
/* consume.c Smythies 2012.06.23
/*         First just try to compile the code as sent
/*         from Peter Zijlstra.
/*         But converted to my coding standards (which will
/*         annoy Peter if it ever gets sent back).
/*
/******************************************************/

#include <sys/time.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>

unsigned long long stamp(void){
   struct timeval tv;

   gettimeofday(&tv, NULL);

   return (unsigned long long)tv.tv_sec * 1000000 + tv.tv_usec;
} /* endprocedure */

void consume(int spin, int total){
   unsigned long long begin, now;

   begin = stamp();

   for (;;) {  /* forever */
      now = stamp();
      if ((long long)(now - begin) > spin) {
         usleep(total - spin);
         begin += total;
      } /* endif */
   } /* endfor */
} /* endprocedure */

int main(int argc, char **argv){
   double frac, freq, period;

   printf("consume: %s %s\n", argv[1], argv[2]);

   switch(argc){
   case 3:
      frac = atof(argv[1]);
      freq = atof(argv[2]);
      break;
   default:
      fprintf(stderr, "%s <frac> <freq>\n  frac   -- [1.0-100.0] %% of time to burn\n  freq -- [hz] (min 1.0) frequency of burn/sleep cycle\n", argv[0]);
      return -1;
   } /* endcase */

   printf("consume: %lf %lf\n", frac, freq);
   if (frac > 100.0){
      frac = 100.0;
   } /* endif */
   if (frac < 1.0){
      frac = 1.0;
   } /* endif */
   if (freq < 1.0){
      freq = 1.0;
   } /* endif */
   period = 1000000.0 / freq;
   printf("consume: %lf %lf %lf\n", frac, freq, period);
   consume((int)(period * frac / 100.0 + 0.5), (int)(period + 0.5));
   return 0;
} /* endprocedure */