/* Program to simulate Budgie Bedlam         */
/* for CPSC 441 Assignment 4, January 2012.  */
/*                                           */
/* Written by Carey Williamson, Jan 12, 2011 */
/* Updated by Carey Williamson, Jan 11, 2012 */
/*                                           */
/*   Usage:  cc -o budgie budgie.c -lm       */
/*           ./budgie                        */

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

/* Constants */
#define N 2                   /* Number of budgies */
#define MEAN_QUIET_TIME 90.0   /* Mean quiet time in minutes */
#define MEAN_SONG_TIME 10.0     /* Mean song time in minutes */

/* Simulation parameters */
#define WARM_UP    10000.0
#define END_TIME 1000000.0

/* Budgie states */
#define QUIET 0
#define SINGING 1

/* Song duration model */
#define EXPONENTIAL 1
/* #define CONSTANT 1 */

/* Debugging flags */
/* #define DEBUG 1 */
/* #define DEBUG2 1 */

/* Parameters for random number generation. */
#define MAX_INT 2147483647       /* Maximum positive integer 2^31 - 1 */

double log();

/* Generate a random floating point number uniformly distributed in [0,1] */
double Uniform01()
  {
    double randnum;
    /* get a random positive integer from random() */
    randnum = (double) 1.0 * random();
    /* divide by max int to get something in the range 0.0 to 1.0  */
    randnum = randnum / (1.0 * MAX_INT); 
    return( randnum );
  }

/* Generate a random floating point number from an exponential    */
/* distribution with mean mu.                                     */

double Exponential(mu)
    double mu;
 {
    double randnum, ans;

    randnum = Uniform01();
    ans = -(mu) * log(randnum);
    return( ans );
  }

main()
  {
    int i;
    int active, nexteventindex, status[N];
    int songtries, perfectsongs;
    int mostrecentsongertostart;
    double mostrecentsongstarttime, mostrecentsongendtime;
    double now, lastcheck, nexteventtime, nextevent[N];
    double randnum;
    double idletime, melodioustime, squawkytime, perfecttime;

    /* initialization */
    now = 0.0;
    lastcheck = 0.0;

    srand(123457);

    idletime = 0.0;
    melodioustime = 0.0;
    squawkytime = 0.0;
    perfecttime = 0.0;

    songtries = 0;
    perfectsongs = 0;

    active = 0;
    for( i = 0; i < N; i++ )
      {
	status[i] = QUIET;
	nextevent[i] = Exponential( MEAN_QUIET_TIME );
#ifdef DEBUG2
	printf("Budgie %d will start singing at time %5.3f\n", i, nextevent[i]);
#endif
      }

    /* main simulation loop */
    while( now < END_TIME )
      {
	/* find next event to happen */
	nexteventtime = END_TIME;
	for( i = 0; i < N; i++ )
	  {
	    if( nextevent[i] < nexteventtime )
	      {
		nexteventtime = nextevent[i];
		nexteventindex = i;
	      }
	  }

#ifdef DEBUG2
	printf("Next event is for Budgie %d at time %5.3f\n", 
	       nexteventindex, nexteventtime);
#endif

	if( nexteventtime < END_TIME )
	  {
	    /* update statistics and determine state transition */
	    now = nexteventtime;
	    if( status[nexteventindex] == QUIET )
	      {
		/* This Budgie is just starting to sing */
		if( active == 0 )
		  idletime += now - lastcheck;
		else if( active == 1 )
		  melodioustime += now - lastcheck;
		else squawkytime += now - lastcheck;
		lastcheck = now;
		songtries++;
		mostrecentsongertostart = nexteventindex;
		mostrecentsongstarttime = now;

#ifdef DEBUG
		for( i = 0; i < active; i++ )
		  printf(" ");
		printf("Budgie %d starting to sing at time %5.3f\n",
		       nexteventindex, now);
#endif
		status[nexteventindex] = SINGING;
#ifdef EXPONENTIAL
		nextevent[nexteventindex] += Exponential( MEAN_SONG_TIME );
#endif
#ifdef CONSTANT
		nextevent[nexteventindex] += MEAN_SONG_TIME;
#endif
		active++;
	      }
	    else
	      {
		/* This Budgie is done singing */
		if( active == 0 )
		  printf("Error keeping track of singing Budgies!!!\n");
		else if( active == 1 )
		  {
		    melodioustime += now - lastcheck;
		    if( (mostrecentsongertostart == nexteventindex) &&
			(mostrecentsongendtime < mostrecentsongstarttime) )
		      perfectsongs++;
		    perfecttime += now - lastcheck;
		  }
		else squawkytime += now - lastcheck;
		lastcheck = now;
		mostrecentsongendtime = now;

		status[nexteventindex] = QUIET;
		active--;
		nextevent[nexteventindex] += Exponential( MEAN_QUIET_TIME );
#ifdef DEBUG
		for( i = 0; i < active; i++ )
		  printf(" ");
		printf("Budgie %d is done singing at time %5.3f\n",
		       nexteventindex, now);
#endif
	      }
	  }
	else
	  {
	    /* time to quit */
	    now = END_TIME;
	    if( active == 0 )
	      idletime += now - lastcheck;
	    else if( active == 1 )
	      melodioustime += now - lastcheck;
	    else squawkytime += now - lastcheck;
	    lastcheck = now;
	  }
      }

    /* print out statistics */
    printf("N = %d, MEAN_QUIET_TIME = %8.6f, MEAN_SONG_TIME = %8.6f\n",
	   N, MEAN_QUIET_TIME, MEAN_SONG_TIME);
    printf("S = %8.6f\n", MEAN_SONG_TIME / (MEAN_QUIET_TIME + MEAN_SONG_TIME));

    printf("Total time observing BLAN: %8.6f\n", now);
    printf("  Idle time on the BLAN:    %8.6f    %8.6f%%\n",
	   idletime, 100.0 * idletime / now);
    printf("  Melodious time on BLAN:   %8.6f    %8.6f%%\n",
	   melodioustime, 100.0 * melodioustime / now);
    printf("  Squawky time on the BLAN: %8.6f    %8.6f%%\n",
	   squawkytime, 100.0 * squawkytime / now);

    printf("\n  Attempted songs: %d\n", songtries);
    printf("  Perfect songs: %d\n", perfectsongs);
    printf("  Perfect songs/Attempted songs: %8.6f (%4.2f%%)\n",
	   1.0*perfectsongs/songtries, 100.0*perfectsongs/songtries);
    printf("  Perfect song time on the BLAN: %8.6f    %8.6f%%\n",
	   perfecttime, 100.0 * perfecttime / now);

    printf("Quiet  Melodious  Squawky\n");
    printf("%8.6f ", idletime/now);
    if( N > 0 )
      printf("%8.6f ", melodioustime/now);
    else printf("0.000000 ");
    if( N > 1 )
      printf("%8.6f ", squawkytime/now);
    else printf("0.000000 ");
    printf("\n");
  }