Horton

Re: Greatest Common Divisor

Vik Fearing <vik.fearing@2ndquadrant.com>

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From: Vik Fearing <vik.fearing@2ndquadrant.com>
To: Fabien COELHO <coelho@cri.ensmp.fr>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Stephen Frost <sfrost@snowman.net>, Dean Rasheed <dean.a.rasheed@gmail.com>, Chapman Flack <chap@anastigmatix.net>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2020-01-04T02:32:34Z
Lists: pgsql-hackers

Attachments

On 03/01/2020 20:14, Fabien COELHO wrote:
>
> Bonsoir Vik,
>
>  +int4gcd_internal(int32 arg1, int32 arg2)
>  +{
>  +       int32   swap;
>  +
>  +       /*
>  +        * Put the greater value in arg1.
>  +        * This would happen automatically in the loop below, but
> avoids  an
>  +        * expensive modulo simulation on some architectures.
>  +        */
>  +       if (arg1 < arg2)
>  +       {
>  +               swap = arg1;
>  +               arg1 = arg2;
>  +               arg2 = swap;
>  +       }
>
>
> The point of swapping is to a void possibly expensive modulo, but this
> should be done on absolute values, otherwise it may not achieve its
> purpose as stated by the comment?


Here is an updated patch fixing that.

-- 

Vik Fearing

Commits

  1. Add functions gcd() and lcm() for integer and numeric types.