rng.h
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rng.h
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	/* rng.h : definitions for using Don Knuth's random number generator.

	To use it:
	1. Call ran_init(seed) with any long seed. (Optional,
	but you will always get the same sequence otherwise.)
	2. Use NEXTRAN to get the next number (0..2^30-1).
	Alternatively, use KRAN(k) to get a random number 0..k-1.
	For large k, KRAN(k) is not quite uniform. In that case
	use GETKRAN(k,var) to set the variable var to a better
	random number 0..k-1.

	Some of these definitions are also in naututil.h.
	*/

	#ifdef __cplusplus
	extern "C" {
	#endif

	extern long *ran_arr_ptr;
	long ran_arr_cycle(void);
	void ran_init(long seed);
	void ran_array(long *aa, int n);

	#ifdef __cplusplus
	}
	#endif

	#define MAXRAN (0x3fffffffL) /* Values are 0..MAXRAN */
	#define NEXTRAN (ran_arr_ptr>=0 ? ran_arr_ptr++ : ran_arr_cycle())
	#define KRAN(k) (NEXTRAN%(k))
	#define RANREAL ((NEXTRAN+0.5)/(MAXRAN+1.0)) /* Uniform (0,1) */

	#define MAXSAFE(k) (((MAXRAN+1)/(k))*(k))
	#define GETKRAN(k,var) {long __getkran; \
	do {__getkran = NEXTRAN;} while (__getkran >= MAXSAFE(k)); \
	var = __getkran % (k);}
	#define INITRANBYTIME ran_init((long)time(NULL))