| From: | Vik Fearing <vik(dot)fearing(at)2ndquadrant(dot)com> |
|---|---|
| To: | Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Stephen Frost <sfrost(at)snowman(dot)net>, Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com>, Chapman Flack <chap(at)anastigmatix(dot)net>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: Greatest Common Divisor |
| Date: | 2020-01-03 22:57:54 |
| Message-ID: | 5bf72c6b-1290-2ba0-770b-8a13e899fd98@2ndquadrant.com |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
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?
Ah, true. How widespread are these architectures that need this special
treatment? Is it really worth handling?
> I'm unsure about gcd(INT_MIN, 0) should error. Possibly 0 would be nicer?
What justification for that do you have?
--
Vik Fearing
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Tom Lane | 2020-01-03 23:00:01 | Re: Greatest Common Divisor |
| Previous Message | Alvaro Herrera | 2020-01-03 22:31:31 | Re: Greatest Common Divisor |