testrand.c

C和指针非常好的一本书.里面的有许多代码可以借鉴.

/*
** Test the randomness of the values produced by rand.
*/

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

/*
**	Arrays to count the relative frequency of various numbers.
*/
int	frequency2[2];
int	frequency3[3];
int	frequency4[4];
int	frequency5[5];
int	frequency6[6];
int	frequency7[7];
int	frequency8[8];
int	frequency9[9];
int	frequency10[10];

/*
**	Arrays to count the cyclic frequency of various numbers.
*/
int	cycle2[2][2];
int	cycle3[3][3];
int	cycle4[4][4];
int	cycle5[5][5];
int	cycle6[6][6];
int	cycle7[7][7];
int	cycle8[8][8];
int	cycle9[9][9];
int	cycle10[10][10];


/*
**	Macro to count both the frequency and cyclic frequency for
**	a specific number.
*/
#define	CHECK( number, f_table, c_table )			\
		remainder = x % number;				\
		f_table[ remainder ] += 1;			\
		c_table[ remainder ][ last_x % number ] += 1

/*
**	Macro to print a frequency table.
*/
#define	PRINT_F( number, f_table )				\
	printf( "\nFrequency of random numbers modulo %d\n\t",	\
	    number ); 						\
	for( i = 0; i < number; i += 1 )			\
		printf( " %5d", f_table[ i ] );			\
	printf( "\n" )

/*
**	Macro to print a cyclic frequency table.
*/
#define PRINT_C( number, c_table )				\
	printf( "\nCyclic frequency of random numbers modulo %d\n", \
	    number );						\
	for( i = 0; i < number; i += 1 ){			\
		printf( "\t" );					\
		for( j = 0; j < number; j += 1 )		\
			printf( " %5d", c_table[ i ][ j ] );	\
		printf( "\n" );					\
	}
			

int
main( int ac, char **av )
{
	int	i;
	int	j;
	int	x;
	int	last_x;
	int	remainder;

	/*
	** If a seed was given, seed the generator.
	*/
	if( ac > 1 )
		srand( atoi( av[ 1 ] ) );

	last_x = rand();

	/*
	** Run the tests.
	*/
	for( i = 0; i < 10000; i += 1 ){
		x = rand();
		CHECK( 2, frequency2, cycle2 );
		CHECK( 3, frequency3, cycle3 );
		CHECK( 4, frequency4, cycle4 );
		CHECK( 5, frequency5, cycle5 );
		CHECK( 6, frequency6, cycle6 );
		CHECK( 7, frequency7, cycle7 );
		CHECK( 8, frequency8, cycle8 );
		CHECK( 9, frequency9, cycle9 );
		CHECK( 10, frequency10, cycle10 );
		last_x = x;
	}

	/*
	** Print the results.
	*/
	PRINT_F( 2, frequency2 );
	PRINT_F( 3, frequency3 );
	PRINT_F( 4, frequency4 );
	PRINT_F( 5, frequency5 );
	PRINT_F( 6, frequency6 );
	PRINT_F( 7, frequency7 );
	PRINT_F( 8, frequency8 );
	PRINT_F( 9, frequency9 );
	PRINT_F( 10, frequency10 );

	PRINT_C( 2, cycle2 );
	PRINT_C( 3, cycle3 );
	PRINT_C( 4, cycle4 );
	PRINT_C( 5, cycle5 );
	PRINT_C( 6, cycle6 );
	PRINT_C( 7, cycle7 );
	PRINT_C( 8, cycle8 );
	PRINT_C( 9, cycle9 );
	PRINT_C( 10, cycle10 );

	return EXIT_SUCCESS;
}