PRNG(9)                FreeBSD Kernel Developer's Manual               PRNG(9)

NAME
     prng - Kernel pseudo-random number generators

SYNOPSIS
     #include <sys/prng.h>

     uint32_t
     prng32(void);

     uint32_t
     prng32_bounded(uint32_t bound);

     uint64_t
     prng64(void);

     uint64_t
     prng64_bounded(uint64_t bound);

DESCRIPTION
   GENERIC PRNG ROUTINES
     prng is a family of fast, non-cryptographic pseudo-random number
     generators.  Unlike random(9), prng32(), prng32_bounded(), prng64(), and
     prng64_bounded() avoid shared global state, removing unnecessary
     contention on SMP systems.  The routines are not explicitly tied to any
     specific implementation, and may produce different specific sequences on
     different hosts, reboots, or versions of FreeBSD.  Different CPUs in SMP
     systems are guaranteed to produce different sequences of integers.

     For cryptographically secure random numbers generated by the random(4)
     kernel cryptographically secure random number generator subsystem, see
     arc4random(9).

     prng32()
             Generate a 32-bit integer uniformly distributed in [0, 2^32-1].

     prng32_bounded(bound)
             Generate an integer uniformly in the range [0, bound-1].

     prng64()
             Generate a 64-bit integer uniformly distributed in [0, 2^64-1].

     prng64_bounded(bound)
             Generate an integer uniformly in the range [0, bound-1].

     These routines are not reentrant; they are not safe to use in interrupt
     handlers ("interrupt filters" in bus_setup_intr(9) terminology).  They
     are safe to use in all other kernel contexts, including interrupt threads
     ("ithreads").

   REPRODUCIBLE PRNG APIS
     In addition to these per-CPU helpers, the <sys/prng.h> header also
     exposes the entire API of the PCG family of PRNGs as inline functions.
     The PCG-C API is described in full at
     https://www.pcg-random.org/using-pcg-c.html.

HISTORY
     prng was introduced in FreeBSD 13.

FreeBSD 13.1-RELEASE-p6         August 5, 2020         FreeBSD 13.1-RELEASE-p6