On 15/04/2014 17:34, David G Johnston wrote: > Raymond O'Donnell wrote >> On 15/04/2014 17:20, David G Johnston wrote: >>> Willy-Bas Loos-3 wrote >>>> Hi, I ran into some strange behavior. Seems like a bug to me? >>>> >>>> wbloos=# select round(0.5::numeric), round(0.5::double precision); >>>> round | round -------+------- 1 | 0 (1 row) >>> >>> Not a bug; and likely to simple to have escaped notice this long so >>> the first reaction should be "what am I missing here?" >>> >>> [google: round .5 postgresql] >>> >>> http://grokbase.com/t/postgresql/pgsql-hackers/03ap11tckn/round-function-wrong/oldest >>> >>> Round( numeric ) - 0.5 rounds away from zero Round( float ) - >>> platform dependent, IEEE 0.5 rounds toward even >>> >>> You can argue the decision but at this point it's not likely to >>> change. >> >> Interestingly, I get different results (on both 9.1.4 and 9.3.0) on >> Windows: >> >> postgres=# select round(0.5::numeric), round(0.5::double precision); >> round | round >> -------+------- >> 1 | 1 >> (1 row) >> >> >> postgres=# select version(); >> version >> ------------------------------------------------------------- >> PostgreSQL 9.1.4, compiled by Visual C++ build 1500, 64-bit >> (1 row) >> >> >> .... Same on 9.3.0. > > I'm not particularly surprised that Windows is not being IEEE compliant, and > instead chooses the more common round-away-from-zero behavior, here though I > am unsure where the dependent implementation would end up existing. Oh, so does the rounding code use OS facilities, then, rather than being implemented in Postgres? - Didn't know that, though I was aware PG does that in other areas (collation, for example). Ray. -- Raymond O'Donnell :: Galway :: Ireland rod@xxxxxx -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
