PostgreSQL Source Code git master
Macros | Functions | Variables
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.

314{
316
317 return (bool) (v >> 63);
318}
uint64_t uint64
Definition: c.h:539
static uint64 xoroshiro128ss(pg_prng_state *state)
Definition: pg_prng.c:54
Definition: regguts.h:323

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.

269{
271
272 /*
273 * As above, assume there's 52 mantissa bits in a double. This result
274 * could round to 1.0 if double's precision is less than that; but we
275 * assume IEEE float arithmetic elsewhere in Postgres, so this seems OK.
276 */
277 return ldexp((double) (v >> (64 - 52)), -52);
278}

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.

291{
292 double u1,
293 u2,
294 z0;
295
296 /*
297 * pg_prng_double generates [0, 1), but for the basic version of the
298 * Box-Muller transform the two uniformly distributed random numbers are
299 * expected to be in (0, 1]; in particular we'd better not compute log(0).
300 */
301 u1 = 1.0 - pg_prng_double(state);
302 u2 = 1.0 - pg_prng_double(state);
303
304 /* Apply Box-Muller transform to get one normal-valued output */
305 z0 = sqrt(-2.0 * log(u1)) * sin(2.0 * M_PI * u2);
306 return z0;
307}
double pg_prng_double(pg_prng_state *state)
Definition: pg_prng.c:268
#define M_PI
Definition: pg_prng.c:29

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.

103{
104 /* Assume there's about 52 mantissa bits; the sign contributes too. */
105 int64 seed = ((double) ((UINT64CONST(1) << 52) - 1)) * fseed;
106
107 pg_prng_seed(state, (uint64) seed);
108}
int64_t int64
Definition: c.h:535
#define UINT64CONST(x)
Definition: c.h:553
void pg_prng_seed(pg_prng_state *state, uint64 seed)
Definition: pg_prng.c:89

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.

244{
246
247 return (int32) (v >> 32);
248}
int32_t int32
Definition: c.h:534

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.

255{
257
258 return (int32) (v >> 33);
259}

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.

174{
175 return (int64) xoroshiro128ss(state);
176}

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.

193{
194 int64 val;
195
196 if (likely(rmax > rmin))
197 {
198 uint64 uval;
199
200 /*
201 * Use pg_prng_uint64_range(). Can't simply pass it rmin and rmax,
202 * since (uint64) rmin will be larger than (uint64) rmax if rmin < 0.
203 */
204 uval = (uint64) rmin +
205 pg_prng_uint64_range(state, 0, (uint64) rmax - (uint64) rmin);
206
207 /*
208 * Safely convert back to int64, avoiding implementation-defined
209 * behavior for values larger than PG_INT64_MAX. Modern compilers
210 * will reduce this to a simple assignment.
211 */
212 if (uval > PG_INT64_MAX)
213 val = (int64) (uval - PG_INT64_MIN) + PG_INT64_MIN;
214 else
215 val = (int64) uval;
216 }
217 else
218 val = rmin;
219
220 return val;
221}
#define likely(x)
Definition: c.h:401
#define PG_INT64_MAX
Definition: c.h:597
#define PG_INT64_MIN
Definition: c.h:596
long val
Definition: informix.c:689
uint64 pg_prng_uint64_range(pg_prng_state *state, uint64 rmin, uint64 rmax)
Definition: pg_prng.c:144

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

Referenced by date_random(), int4random(), int8random(), timestamp_random(), and timestamptz_random().

◆ pg_prng_int64p()

int64 pg_prng_int64p ( pg_prng_state *  state )

Definition at line 182 of file pg_prng.c.

183{
184 return (int64) (xoroshiro128ss(state) & UINT64CONST(0x7FFFFFFFFFFFFFFF));
185}

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.

90{
91 state->s0 = splitmix64(&seed);
92 state->s1 = splitmix64(&seed);
93 /* Let's just make sure we didn't get all-zeroes */
95}
static uint64 splitmix64(uint64 *state)
Definition: pg_prng.c:72
bool pg_prng_seed_check(pg_prng_state *state)
Definition: pg_prng.c:114

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(), test_random(), and test_random_operations().

◆ pg_prng_seed_check()

bool pg_prng_seed_check ( pg_prng_state *  state )

Definition at line 114 of file pg_prng.c.

115{
116 /*
117 * If the seeding mechanism chanced to produce all-zeroes, insert
118 * something nonzero. Anything would do; use Knuth's LCG parameters.
119 */
120 if (unlikely(state->s0 == 0 && state->s1 == 0))
121 {
122 state->s0 = UINT64CONST(0x5851F42D4C957F2D);
123 state->s1 = UINT64CONST(0x14057B7EF767814F);
124 }
125
126 /* As a convenience for the pg_prng_strong_seed macro, return true */
127 return true;
128}
#define unlikely(x)
Definition: c.h:402

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.

228{
229 /*
230 * Although xoroshiro128** is not known to have any weaknesses in
231 * randomness of low-order bits, we prefer to use the upper bits of its
232 * result here and below.
233 */
235
236 return (uint32) (v >> 32);
237}
uint32_t uint32
Definition: c.h:538

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(), test_huge_distances(), and test_random_operations().

◆ pg_prng_uint64()

uint64 pg_prng_uint64 ( pg_prng_state *  state )

Definition at line 134 of file pg_prng.c.

135{
136 return xoroshiro128ss(state);
137}

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.

145{
146 uint64 val;
147
148 if (likely(rmax > rmin))
149 {
150 /*
151 * Use bitmask rejection method to generate an offset in 0..range.
152 * Each generated val is less than twice "range", so on average we
153 * should not have to iterate more than twice.
154 */
155 uint64 range = rmax - rmin;
156 uint32 rshift = 63 - pg_leftmost_one_pos64(range);
157
158 do
159 {
160 val = xoroshiro128ss(state) >> rshift;
161 } while (val > range);
162 }
163 else
164 val = 0;
165
166 return rmin + val;
167}
static int pg_leftmost_one_pos64(uint64 word)
Definition: pg_bitutils.h:72
static struct cvec * range(struct vars *v, chr a, chr b, int cases)
Definition: regc_locale.c:412

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

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

◆ rotl()

static uint64 rotl ( uint64  x,
int  bits 
)
inlinestatic

Definition at line 41 of file pg_prng.c.

42{
43 return (x << bits) | (x >> (64 - bits));
44}
x
int x
Definition: isn.c:75

References x.

Referenced by xoroshiro128ss().

◆ splitmix64()

static uint64 splitmix64 ( uint64 *  state )
static

Definition at line 72 of file pg_prng.c.

73{
74 /* state update */
75 uint64 val = (*state += UINT64CONST(0x9E3779B97f4A7C15));
76
77 /* value extraction */
78 val = (val ^ (val >> 30)) * UINT64CONST(0xBF58476D1CE4E5B9);
79 val = (val ^ (val >> 27)) * UINT64CONST(0x94D049BB133111EB);
80
81 return val ^ (val >> 31);
82}

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.

55{
56 uint64 s0 = state->s0,
57 sx = state->s1 ^ s0,
58 val = rotl(s0 * 5, 7) * 9;
59
60 /* update state */
61 state->s0 = rotl(s0, 24) ^ sx ^ (sx << 16);
62 state->s1 = rotl(sx, 37);
63
64 return val;
65}
static uint64 rotl(uint64 x, int bits)
Definition: pg_prng.c:41

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(), get_permutation(), 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_duplicates(), test_huge_distances(), test_pattern(), test_remove_node(), testdelete(), and testfindltgt().

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