Date: Fri, 3 Jan 2020 20:14:13 +0100 (CET)
From: Fabien COELHO <coelho@cri.ensmp.fr>
To: Vik Fearing <vik.fearing@2ndquadrant.com>
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>
Subject: Re: Greatest Common Divisor
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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?

> gcd() is now strictly positive, so INT_MIN is no longer a valid result.

Ok.

I'm unsure about gcd(INT_MIN, 0) should error. Possibly 0 would be 
nicer?

-- 
Fabien.