From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | "Merlin Moncure" <merlin(dot)moncure(at)rcsonline(dot)com> |
Cc: | pgsql-hackers-win32(at)postgresql(dot)org |
Subject: | Re: win32 random number generator |
Date: | 2005-08-22 20:47:46 |
Message-ID: | 21049.1124743666@sss.pgh.pa.us |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers-win32 |
"Merlin Moncure" <merlin(dot)moncure(at)rcsonline(dot)com> writes:
> The windows random number of generator (a port of lrand48 in random.c)
> seems a little weak. It seems to only offer about 16 bits of precision.
> Maybe there is a bug in the implementation?
> esp=# select count(*) from (select distinct random() from
> generate_series(1,1000000)) q;
> count
> -------
> 65559
> (1 row)
That's pretty awful, all right. I get numbers like this on two
different Unix machines:
regression=# select count(*) from (select distinct random() from generate_series(1,1000000)) q;
count
--------
999769
(1 row)
postgres=# select count(*) from (select distinct random() from
postgres(# generate_series(1,1000000)) q;
count
--------
999787
(1 row)
Anyone care to burrow into the code and see what its problem is?
regards, tom lane
From | Date | Subject | |
---|---|---|---|
Next Message | Merlin Moncure | 2005-08-22 20:59:13 | Re: win32 random number generator |
Previous Message | Merlin Moncure | 2005-08-22 19:59:57 | win32 random number generator |