srandom(3m) [hpux man page]

random(3M)																random(3M)

NAME

       random(), srandom(), initstate(), setstate() - generate a pseudorandom number

SYNOPSIS

DESCRIPTION

       The and functions are random-number generators that have virtually the same calling sequence and initialization properties as the and func-
       tions, but produce sequences that are more random.  The low 12 bits generated by the function go through a cyclic pattern,  while  all  the
       bits generated by the function are usable.  For example, produces a random binary value.

       The  function uses a nonlinear additive feedback random-number generator employing a default state array size of 31 long integers to return
       successive pseudorandom numbers in the range from 0 to The period of this random-number generator is approximately 16 x	The  size  of  the
       state array determines the period of the random-number generator.  Increasing the state array size increases the period.

       With 256 bytes of state information, the period of the random-number generator is greater than

       Like  the function, the function produces by default a sequence of numbers that can be duplicated by calling the function with a value of 1
       as the seed.

       The function initializes the current state array using the value of seed.

       The and functions handle restarting and changing random-number generators.  The function allows a state array,  pointed	to  by	the  state
       argument,  to be initialized for future use.  The size argument, which specifies the size in bytes of the state array, is used by the func-
       tion to decide how sophisticated a random-number generator to use; the larger the state array, the more random the numbers.  Values for the
       amount  of  state  information are 8, 32, 64, 128, and 256 bytes.  Amounts less than 8 bytes return a NULL pointer, while other amounts are
       rounded down to the nearest known value.  The seed argument specifies a starting point for the  random-number  sequence	and  provides  for
       restarting at the same point.  The function returns a pointer to the previous state information array.

       Once a state has been initialized, the function allows switching between state arrays.  The array defined by the state argument is used for
       further random-number generation until the function is called or the function is called again.  The function returns a pointer to the  pre-
       vious state array.

       After initialization, a state array can be restarted at a different point in one of two ways:

	      The function can be used, with the desired seed, state array, and size of the array.

	      The  function,  with the desired state, can be used, followed by the function with the desired seed.  The advantage of using both of
	      these functions is that the size of the state array does not have to be saved once it is initialized.

RETURN VALUE

       The function returns the generated pseudorandom number.

       The function returns no value.

       Upon successful completion, the and functions return a pointer to the previous state array.  Otherwise, a NULL pointer is returned.

ERRORS

       If the function detects that the state information has been damaged, error messages are written to standard error.

SEE ALSO

       drand48(3C), rand(3C), random(7).

STANDARDS CONFORMANCE

																	random(3M)

Check Out this Related Man Page

random(3)						     Library Functions Manual							 random(3)

Name
       random, srandom, initstate, setstate - better random number generator; routines for changing generators

Syntax
       long random()

       void srandom(seed)
       int seed;

       char *initstate(seed, state, n)
       unsigned seed;
       char *state;
       int n;

       char *setstate(state)
       char *state;

Description
       The  subroutine	uses  a  non-linear additive feedback random number generator employing a default table of size 31 long integers to return
       successive pseudo-random numbers in the range from 0 to (2**31)-1.  The period of this random number generator is very large, approximately
       16*((2**31)-1).

       The  subroutines  have  (almost)  the same calling sequence and initialization properties as The difference is that rand(3) produces a much
       less random sequence - in fact, the low dozen bits generated by rand go through a cyclic pattern.  All the bits generated  by  are  usable.
       For example, "random()&01" will produce a random binary value.

       Unlike  does  not  return  the  old seed; the reason for this is that the amount of state information used is much more than a single word.
       (Two other routines are provided to deal with restarting/changing random number generators.)  Like  however,  will  by  default	produce  a
       sequence of numbers that can be duplicated by calling with 1 as the seed.

       The  routine  allows  a state array, passed in as an argument, to be initialized for future use.  The size of the state array (in bytes) is
       used by to decide how sophisticated a random number generator it should use - the more state, the better the random numbers will be.  (Cur-
       rent  "optimal"	values	for  the  amount of state information are 8, 32, 64, 128, and 256 bytes; other amounts will be rounded down to the
       nearest known amount.  Using less than 8 bytes will cause an error).  The seed for the initialization (which specifies a starting point for
       the  random  number  sequence, and provides for restarting at the same point) is also an argument.  returns a pointer to the previous state
       information array.

       Once a state has been initialized, the routine provides for rapid switching between states.  The subroutine returns a pointer to the previ-
       ous state array; its argument state array is used for further random number generation until the next call to or

       Once  a	state  array  has  been  initialized, it may be restarted at a different point either by calling (with the desired seed, the state
       array, and its size) or by calling both (with the state array) and (with the desired seed).  The advantage of calling both and is that  the
       size of the state array does not have to be remembered after it is initialized.

       With  256  bytes  of  state information, the period of the random number generator is greater than 269, which should be sufficient for most
       purposes.

Diagnostics
       If is called with less than 8 bytes of state information, or if detects that the state information has been  garbled,  error  messages  are
       printed on the standard error output.

See Also
       rand(3)

																	 random(3)

Linux and UNIX Man Pages

srandom(3m) [hpux man page]

Check Out this Related Man Page