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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2021-11-28 21:32:36 -0500 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2021-11-28 21:33:07 -0500 |
| commit | 3804539e48e794781c6145c7f988f5d507418fa8 (patch) | |
| tree | 317904b43ca8c1d510b23cb8fdd7b05a75e971bc /contrib/tablefunc/tablefunc.c | |
| parent | f44ceb46ec2d8da48f6e145bf462d5620c25e079 (diff) | |
| download | postgresql-3804539e48e794781c6145c7f988f5d507418fa8.tar.gz postgresql-3804539e48e794781c6145c7f988f5d507418fa8.zip | |
Replace random(), pg_erand48(), etc with a better PRNG API and algorithm.
Standardize on xoroshiro128** as our basic PRNG algorithm, eliminating
a bunch of platform dependencies as well as fundamentally-obsolete PRNG
code. In addition, this API replacement will ease replacing the
algorithm again in future, should that become necessary.
xoroshiro128** is a few percent slower than the drand48 family,
but it can produce full-width 64-bit random values not only 48-bit,
and it should be much more trustworthy. It's likely to be noticeably
faster than the platform's random(), depending on which platform you
are thinking about; and we can have non-global state vectors easily,
unlike with random(). It is not cryptographically strong, but neither
are the functions it replaces.
Fabien Coelho, reviewed by Dean Rasheed, Aleksander Alekseev, and myself
Discussion: https://postgr.es/m/alpine.DEB.2.22.394.2105241211230.165418@pseudo
Diffstat (limited to 'contrib/tablefunc/tablefunc.c')
| -rw-r--r-- | contrib/tablefunc/tablefunc.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/contrib/tablefunc/tablefunc.c b/contrib/tablefunc/tablefunc.c index 52b272f2989..63bb91a646f 100644 --- a/contrib/tablefunc/tablefunc.c +++ b/contrib/tablefunc/tablefunc.c @@ -36,6 +36,7 @@ #include "access/htup_details.h" #include "catalog/pg_type.h" +#include "common/pg_prng.h" #include "executor/spi.h" #include "funcapi.h" #include "lib/stringinfo.h" @@ -290,8 +291,8 @@ get_normal_pair(float8 *x1, float8 *x2) do { - u1 = (float8) random() / (float8) MAX_RANDOM_VALUE; - u2 = (float8) random() / (float8) MAX_RANDOM_VALUE; + u1 = pg_prng_double(&pg_global_prng_state); + u2 = pg_prng_double(&pg_global_prng_state); v1 = (2.0 * u1) - 1.0; v2 = (2.0 * u2) - 1.0; |