Re: Rounding strategy

Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at> writes:
> On Mon, 2021-04-19 at 08:00 +0000, PG Doc comments form wrote:
>> The 'round' mathematical function documentation doesn't specify its rounding
>> strategy. If this would be documented then users can rely on its rounding
>> behavior. For double precision the rounding probably depends on your
>> platform. For numeric the function seems to round to nearest with ties going
>> away from zero (sometimes referred to as "round half up). 6.5 -> 7.0 and
>> -6.5 -> -7.0.

> Here is a proposed patch.

LGTM, although I think we can be a bit more specific about the float
case. I suggest

... by rounding away from 0. For <type>double precision</type>,
the tie-breaking behavior is platform dependent, but
<quote>round to nearest even</quote> is the most common rule.

regards, tom lane