Question to datatype.sgml

On 30/12/2019 01:34, Tatsuo Ishii wrote:

Hi,

Can you please someone elaborate what's the meaning of "even" in
datatype.sgml?

<para>
By default, floating point values are output in text form in their
shortest precise decimal representation; the decimal value produced is
closer to the true stored binary value than to any other value
representable in the same binary precision. (However, the output value is
currently never <emphasis>exactly</emphasis> midway between two
representable values, in order to avoid a widespread bug where input
routines do not properly respect the round-to-even rule.) This value will
~~~~~~~~~~~~~~~~~~~
use at most 17 significant decimal digits for <type>float8</type>
values, and at most 9 digits for <type>float4</type> values.
</para>

I think "even" means "equality" here, not "even" of "even and odd".

It does actually mean "even and odd".  This kind of rounding is also
called "Banker's Rounding".

https://en.wikipedia.org/wiki/Rounding#Round_half_to_even

--

Vik Fearing

On 30/12/2019 01:34, Tatsuo Ishii wrote:

Hi,

Can you please someone elaborate what's the meaning of "even" in
datatype.sgml?

<para>
By default, floating point values are output in text form in their
shortest precise decimal representation; the decimal value produced is
closer to the true stored binary value than to any other value
representable in the same binary precision. (However, the output value is
currently never <emphasis>exactly</emphasis> midway between two
representable values, in order to avoid a widespread bug where input
routines do not properly respect the round-to-even rule.) This value will
~~~~~~~~~~~~~~~~~~~
use at most 17 significant decimal digits for <type>float8</type>
values, and at most 9 digits for <type>float4</type> values.
</para>

I think "even" means "equality" here, not "even" of "even and odd".

It does actually mean "even and odd".  This kind of rounding is also
called "Banker's Rounding".

https://en.wikipedia.org/wiki/Rounding#Round_half_to_even

Oh, Thanks! The link is very helpful.
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese:http://www.sraoss.co.jp

Tatsuo Ishii <ishii@sraoss.co.jp> writes:

Can you please someone elaborate what's the meaning of "even" in
datatype.sgml?

representable values, in order to avoid a widespread bug where input
routines do not properly respect the round-to-even rule.) This value will

It does actually mean "even and odd". This kind of rounding is also
called "Banker's Rounding".
https://en.wikipedia.org/wiki/Rounding#Round_half_to_even

Oh, Thanks! The link is very helpful.

I think actually the standard terminology is "round-to-nearest-even".

regards, tom lane

It does actually mean "even and odd". This kind of rounding is also
called "Banker's Rounding".
https://en.wikipedia.org/wiki/Rounding#Round_half_to_even

Oh, Thanks! The link is very helpful.

I think actually the standard terminology is "round-to-nearest-even".

Ok, I will change it to "round-to-nearest-even" if there's no objection.

Best regards,
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese:http://www.sraoss.co.jp

I think actually the standard terminology is "round-to-nearest-even".

Ok, I will change it to "round-to-nearest-even" if there's no objection.

Done.

Best regards,
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese:http://www.sraoss.co.jp