/* +++Date last modified: 05-Jul-1997 */



/*

**  longrand() -- generate 2**31-2 random numbers

**

**  public domain by Ray Gardner

**

**  based on "Random Number Generators: Good Ones Are Hard to Find",

**  S.K. Park and K.W. Miller, Communications of the ACM 31:10 (Oct 1988),

**  and "Two Fast Implementations of the 'Minimal Standard' Random

**  Number Generator", David G. Carta, Comm. ACM 33, 1 (Jan 1990), p. 87-88

**

**  linear congruential generator f(z) = 16807 z mod (2 ** 31 - 1)

**

**  uses L. Schrage's method to avoid overflow problems

*/



#define a 16807         /* multiplier */

#define m 2147483647L   /* 2**31 - 1 */

#define q 127773L       /* m div a */

#define r 2836          /* m mod a */



long nextlongrand(long seed)

{

      unsigned long lo, hi;



      lo = a * (long)(seed & 0xFFFF);

		hi = a * (long)((unsigned long)seed >> 16);

      lo += (hi & 0x7FFF) << 16;

      if (lo > m)

		{

            lo &= m;

            ++lo;

		}

      lo += hi >> 15;

      if (lo > m)

		{

            lo &= m;

            ++lo;

		}

      return (long)lo;

}



static long randomnum = 1;



long longrand(void)                     /* return next random long */

{

      randomnum = nextlongrand(randomnum);

		return randomnum;

}



void slongrand(unsigned long seed)      /* to seed it */

{

		randomnum = seed ? (seed & m) : 1;  /* nonzero seed */

}