From 3804539e48e794781c6145c7f988f5d507418fa8 Mon Sep 17 00:00:00 2001
From: Tom Lane
Date: Sun, 28 Nov 2021 21:32:36 -0500
Subject: 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
---
 contrib/tablefunc/tablefunc.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

(limited to 'contrib/tablefunc/tablefunc.c')

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;
-- 
cgit v1.2.3