/*
 * Test for simple generation of distribution and sort.
 *
 * Telford Tendys, Copyright (C) 2017
 *
 * This program may be re-distributed without modification.
 */

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

#define NUM_PEOPLE     1000000

double cq[ NUM_PEOPLE ];

double Box_Muller( void )
{
	for(;;)
	{
		double bm;

		double u = random();
		double v = random();
		u /= RAND_MAX;
		v /= RAND_MAX;

		bm = sqrt( -2 * log( u )) * cos( 2 * M_PI * v );
		/*
		 * Note that standard normal has mean of 0 and SD of 1,
		 * but Psychologist normal is mean 100, and SD of 15.
		 * Also for no particular reason, reject the possibility
		 * of anything being below 0 nor greater than 200.
		 */
		bm *= 15;
		bm += 100;
		if( bm >= 0 && bm <= 200 ) { return( bm ); }
	}
}

int cq_compar( const void *p1, const void *p2 )
{
	register const double *dp1;
	register const double *dp2;

	dp1 = p1;
	dp2 = p2;
	if( *dp1 > *dp2 ) { return( 1 ); }
	if( *dp1 < *dp2 ) { return( -1 ); }
	/* Not expecting any NaN, Inf, etc */
	return( 0 );
}

/*
 * Very simple array fill with normal random numbers.
 * Then sort the array from lowest to highest.
 */
int fill_cq()
{
	int i;

	/*
	 * Put a bunch of normally distributed random numbers together
	 */
	for( i = 0; i < NUM_PEOPLE; i++ )
	{
		cq[ i ] = Box_Muller();
	}

	/*
 	 * Sort the stack (standard library sort function)
	 */
	qsort( cq, NUM_PEOPLE, sizeof( cq[ 0 ]), &cq_compar );
	return( 0 );
}

int main( void )
{
	int i, refil;
	FILE *fp;

	srand( 123456 );
	fill_cq();

	/* Dump out a basic set of CQ numbers to show population */
	fp = fopen( "population_cq.dat", "w" );
	fprintf( fp, "CQ\n" );
	for( i = 0; i < NUM_PEOPLE; i++ )
	{
		fprintf( fp, "%f\n", cq[ i ]);
	}
	fclose( fp );
	return( 0 );
}