pg_prng.c File Reference

#include "c.h"
#include <math.h>
#include "common/pg_prng.h"
#include "port/pg_bitutils.h"

Include dependency graph for pg_prng.c:

Go to the source code of this file.

Macros
#define	M_PI   3.14159265358979323846

Functions
static uint64	rotl (uint64 x, int bits)
static uint64	xoroshiro128ss (pg_prng_state *state)
static uint64	splitmix64 (uint64 *state)
void	pg_prng_seed (pg_prng_state *state, uint64 seed)
void	pg_prng_fseed (pg_prng_state *state, double fseed)
bool	pg_prng_seed_check (pg_prng_state *state)
uint64	pg_prng_uint64 (pg_prng_state *state)
uint64	pg_prng_uint64_range (pg_prng_state *state, uint64 rmin, uint64 rmax)
int64	pg_prng_int64 (pg_prng_state *state)
int64	pg_prng_int64p (pg_prng_state *state)
int64	pg_prng_int64_range (pg_prng_state *state, int64 rmin, int64 rmax)
uint32	pg_prng_uint32 (pg_prng_state *state)
int32	pg_prng_int32 (pg_prng_state *state)
int32	pg_prng_int32p (pg_prng_state *state)
double	pg_prng_double (pg_prng_state *state)
double	pg_prng_double_normal (pg_prng_state *state)
bool	pg_prng_bool (pg_prng_state *state)

Variables
pg_prng_state	pg_global_prng_state

Macro Definition Documentation

M_PI

#define M_PI   3.14159265358979323846

Definition at line 29 of file pg_prng.c.

Function Documentation

pg_prng_bool()

bool pg_prng_bool

(

pg_prng_state *

state

)

Definition at line 313 of file pg_prng.c.

{
    uint64      v = xoroshiro128ss(state);
 
    return (bool) (v >> 63);
}

References xoroshiro128ss().

Referenced by gistchoose().

pg_prng_double()

double pg_prng_double

(

pg_prng_state *

state

)

Definition at line 268 of file pg_prng.c.

{
    uint64      v = xoroshiro128ss(state);
 
    /*
     * As above, assume there's 52 mantissa bits in a double.  This result
     * could round to 1.0 if double's precision is less than that; but we
     * assume IEEE float arithmetic elsewhere in Postgres, so this seems OK.
     */
    return ldexp((double) (v >> (64 - 52)), -52);
}

References xoroshiro128ss().

Referenced by check_log_duration(), computeIterativeZipfian(), doLog(), drandom(), explain_ExecutorStart(), geqo_rand(), get_normal_pair(), getExponentialRand(), getPoissonRand(), perform_spin_delay(), pg_prng_double_normal(), sampler_random_fract(), and StartTransaction().

pg_prng_double_normal()

double pg_prng_double_normal

(

pg_prng_state *

state

)

Definition at line 290 of file pg_prng.c.

{
    double      u1,
                u2,
                z0;
 
    /*
     * pg_prng_double generates [0, 1), but for the basic version of the
     * Box-Muller transform the two uniformly distributed random numbers are
     * expected to be in (0, 1]; in particular we'd better not compute log(0).
     */
    u1 = 1.0 - pg_prng_double(state);
    u2 = 1.0 - pg_prng_double(state);
 
    /* Apply Box-Muller transform to get one normal-valued output */
    z0 = sqrt(-2.0 * log(u1)) * sin(2.0 * M_PI * u2);
    return z0;
}

References M_PI, and pg_prng_double().

Referenced by drandom_normal(), and getGaussianRand().

pg_prng_fseed()

void pg_prng_fseed	(	pg_prng_state *	state,
		double	fseed
	)

Definition at line 102 of file pg_prng.c.

{
    /* Assume there's about 52 mantissa bits; the sign contributes too. */
    int64       seed = ((double) ((UINT64CONST(1) << 52) - 1)) * fseed;
 
    pg_prng_seed(state, (uint64) seed);
}

References pg_prng_seed(), and UINT64CONST.

Referenced by geqo_set_seed(), and setseed().

pg_prng_int32()

int32 pg_prng_int32

(

pg_prng_state *

state

)

Definition at line 243 of file pg_prng.c.

{
    uint64      v = xoroshiro128ss(state);
 
    return (int32) (v >> 32);
}

References xoroshiro128ss().

Referenced by prepare_buf().

pg_prng_int32p()

int32 pg_prng_int32p

(

pg_prng_state *

state

)

Definition at line 254 of file pg_prng.c.

{
    uint64      v = xoroshiro128ss(state);
 
    return (int32) (v >> 33);
}

References xoroshiro128ss().

Referenced by create_and_test_bloom().

pg_prng_int64()

int64 pg_prng_int64

(

pg_prng_state *

state

)

Definition at line 173 of file pg_prng.c.

{
    return (int64) xoroshiro128ss(state);
}

References xoroshiro128ss().

pg_prng_int64_range()

int64 pg_prng_int64_range	(	pg_prng_state *	state,
		int64	rmin,
		int64	rmax
	)

Definition at line 192 of file pg_prng.c.

{
    int64       val;
 
    if (likely(rmax > rmin))
    {
        uint64      uval;
 
        /*
         * Use pg_prng_uint64_range().  Can't simply pass it rmin and rmax,
         * since (uint64) rmin will be larger than (uint64) rmax if rmin < 0.
         */
        uval = (uint64) rmin +
            pg_prng_uint64_range(state, 0, (uint64) rmax - (uint64) rmin);
 
        /*
         * Safely convert back to int64, avoiding implementation-defined
         * behavior for values larger than PG_INT64_MAX.  Modern compilers
         * will reduce this to a simple assignment.
         */
        if (uval > PG_INT64_MAX)
            val = (int64) (uval - PG_INT64_MIN) + PG_INT64_MIN;
        else
            val = (int64) uval;
    }
    else
        val = rmin;
 
    return val;
}

References likely, PG_INT64_MAX, PG_INT64_MIN, pg_prng_uint64_range(), and val.

Referenced by int4random(), and int8random().

pg_prng_int64p()

int64 pg_prng_int64p

(

pg_prng_state *

state

)

Definition at line 182 of file pg_prng.c.

{
    return (int64) (xoroshiro128ss(state) & UINT64CONST(0x7FFFFFFFFFFFFFFF));
}

References UINT64CONST, and xoroshiro128ss().

pg_prng_seed()

void pg_prng_seed	(	pg_prng_state *	state,
		uint64	seed
	)

Definition at line 89 of file pg_prng.c.

{
    state->s0 = splitmix64(&seed);
    state->s1 = splitmix64(&seed);
    /* Let's just make sure we didn't get all-zeroes */
    (void) pg_prng_seed_check(state);
}

References pg_prng_seed_check(), and splitmix64().

Referenced by choose_dsm_implementation(), initialize_prng(), InitProcessGlobals(), initRandomState(), libpq_prng_init(), main(), permute(), pg_prng_fseed(), sampler_random_init_state(), set_random_seed(), setup_publisher(), and test_random().

pg_prng_seed_check()

bool pg_prng_seed_check

(

pg_prng_state *

state

)

Definition at line 114 of file pg_prng.c.

{
    /*
     * If the seeding mechanism chanced to produce all-zeroes, insert
     * something nonzero.  Anything would do; use Knuth's LCG parameters.
     */
    if (unlikely(state->s0 == 0 && state->s1 == 0))
    {
        state->s0 = UINT64CONST(0x5851F42D4C957F2D);
        state->s1 = UINT64CONST(0x14057B7EF767814F);
    }
 
    /* As a convenience for the pg_prng_strong_seed macro, return true */
    return true;
}

References UINT64CONST, and unlikely.

Referenced by pg_prng_seed().

pg_prng_uint32()

uint32 pg_prng_uint32

(

pg_prng_state *

state

)

Definition at line 227 of file pg_prng.c.

{
    /*
     * Although xoroshiro128** is not known to have any weaknesses in
     * randomness of low-order bits, we prefer to use the upper bits of its
     * result here and below.
     */
    uint64      v = xoroshiro128ss(state);
 
    return (uint32) (v >> 32);
}

References xoroshiro128ss().

Referenced by _bt_findinsertloc(), acquire_sample_rows(), anl_init_selection_state(), anl_random_fract(), CatalogCacheCreateEntry(), choose_dsm_implementation(), dsm_create(), dsm_postmaster_startup(), ExecInitSampleScan(), generate_object_name(), heap_vacuum_eager_scan_setup(), InitProcessGlobals(), make_main_region_dsm_handle(), reservoir_init_selection_state(), and test_huge_distances().

pg_prng_uint64()

uint64 pg_prng_uint64

(

pg_prng_state *

state

)

Definition at line 134 of file pg_prng.c.

{
    return xoroshiro128ss(state);
}

References xoroshiro128ss().

Referenced by bt_check_every_level(), initRandomState(), main(), permute(), and test_random().

pg_prng_uint64_range()

uint64 pg_prng_uint64_range	(	pg_prng_state *	state,
		uint64	rmin,
		uint64	rmax
	)

Definition at line 144 of file pg_prng.c.

{
    uint64      val;
 
    if (likely(rmax > rmin))
    {
        /*
         * Use bitmask rejection method to generate an offset in 0..range.
         * Each generated val is less than twice "range", so on average we
         * should not have to iterate more than twice.
         */
        uint64      range = rmax - rmin;
        uint32      rshift = 63 - pg_leftmost_one_pos64(range);
 
        do
        {
            val = xoroshiro128ss(state) >> rshift;
        } while (val > range);
    }
    else
        val = 0;
 
    return rmin + val;
}

References likely, pg_leftmost_one_pos64(), range(), val, and xoroshiro128ss().

Referenced by array_shuffle_n(), geqo_randint(), GetPermutation(), getrand(), permute(), pg_prng_int64_range(), pqConnectOptions2(), PQconnectPoll(), random_var(), SetTempTablespaces(), spgdoinsert(), test_pattern(), testdelete(), and testfindltgt().

rotl()

static uint64 rotl ( uint64  x, int  bits  )

inlinestatic

Definition at line 41 of file pg_prng.c.

{
    return (x << bits) | (x >> (64 - bits));
}

References x.

Referenced by xoroshiro128ss().

splitmix64()

static uint64 splitmix64 ( uint64 *  state )

static

Definition at line 72 of file pg_prng.c.

{
    /* state update */
    uint64      val = (*state += UINT64CONST(0x9E3779B97f4A7C15));
 
    /* value extraction */
    val = (val ^ (val >> 30)) * UINT64CONST(0xBF58476D1CE4E5B9);
    val = (val ^ (val >> 27)) * UINT64CONST(0x94D049BB133111EB);
 
    return val ^ (val >> 31);
}

References UINT64CONST, and val.

Referenced by pg_prng_seed().

xoroshiro128ss()

static uint64 xoroshiro128ss ( pg_prng_state *  state )

static

Definition at line 54 of file pg_prng.c.

{
    uint64      s0 = state->s0,
                sx = state->s1 ^ s0,
                val = rotl(s0 * 5, 7) * 9;
 
    /* update state */
    state->s0 = rotl(s0, 24) ^ sx ^ (sx << 16);
    state->s1 = rotl(sx, 37);
 
    return val;
}

References rotl(), and val.

Referenced by pg_prng_bool(), pg_prng_double(), pg_prng_int32(), pg_prng_int32p(), pg_prng_int64(), pg_prng_int64p(), pg_prng_uint32(), pg_prng_uint64(), and pg_prng_uint64_range().

Variable Documentation

pg_global_prng_state

pg_prng_state pg_global_prng_state

Definition at line 34 of file pg_prng.c.

Referenced by _bt_findinsertloc(), acquire_sample_rows(), anl_init_selection_state(), anl_random_fract(), array_shuffle_n(), bt_check_every_level(), CatalogCacheCreateEntry(), check_log_duration(), create_and_test_bloom(), dsm_create(), dsm_postmaster_startup(), ExecInitSampleScan(), explain_ExecutorStart(), get_normal_pair(), GetPermutation(), gistchoose(), heap_vacuum_eager_scan_setup(), InitProcessGlobals(), main(), make_main_region_dsm_handle(), perform_spin_delay(), prepare_buf(), reservoir_init_selection_state(), SetTempTablespaces(), spgdoinsert(), StartTransaction(), test_huge_distances(), test_pattern(), testdelete(), and testfindltgt().