From: | Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com> |
---|---|
To: | nospam-pg-abuse(at)bloodgate(dot)com |
Cc: | PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Some improvements to numeric sqrt() and ln() |
Date: | 2020-03-03 13:42:20 |
Message-ID: | CAEZATCWi1+8ExgPLk=bpEC=jxzjM5Bzch20nfhF7UaQWCC5dhQ@mail.gmail.com |
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Lists: | pgsql-hackers |
On Tue, 3 Mar 2020 at 00:17, Tels <nospam-pg-abuse(at)bloodgate(dot)com> wrote:
>
> Thank you for these patches, these sound like really nice improvements.
Thanks for looking!
> One thing can to my mind while reading the patch:
>
> + * If r < 0 Then
> + * Let r = r + 2*s - 1
> + * Let s = s - 1
>
> This can be reformulated as:
>
> + * If r < 0 Then
> + * Let r = r + s
> + * Let s = s - 1
> + * Let r = r + s
>
> which would remove one mul/shift and the temp. variable.
Good point, that's a neat little optimisation.
I wasn't able to detect any difference in performance, because those
corrections are only triggered about 1 time in every 50 or so, but it
looks neater to me, especially in the numeric iterations, where it
saves a sub_var() by const_one as well as not using the temporary
variable.
Regards,
Dean
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