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From: Tom Lane <[email protected]>
To: Laurenz Albe <[email protected]>
Cc: [email protected]
Cc: [email protected]
Subject: Re: Rounding strategy
Date: Thu, 22 Apr 2021 13:50:20 -0400
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
	<[email protected]>
	<[email protected]>

Laurenz Albe <[email protected]> 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

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