It looks to me like you are rounding on each iteration of the for-loop:
+ for (i = 0; rate > 9999 && i <= 3; i++) {
+ rtmp = rate / 1000;
+ if (rtmp < 9999)
+ rtmp += (rate % 1000) / 500;
+ rate = rtmp;
+ }
Am I missing something?
I'll post my patch on Tuesday.
Yes, I understand that systat can display only 4 digits for BW.
That's 5 digits with my guard digit, which is shifted out (and not displayed)
at the end.
So, with the guard digit, 6 digits is too many.
--------------------------------------------
On Sun, 5/14/17, Mike Belopuhov <m...@belopuhov.com> wrote:
Subject: Re: pf queue definition: bandwidth resolution problem
To: "Carl Mascott" <cmasc...@yahoo.com>
Cc: tech@openbsd.org, t...@openbsd.org
Date: Sunday, May 14, 2017, 4:05 PM
On Sun, May 14, 2017 at 19:48 +0000, Carl
Mascott wrote:
> I have a suggestion RE
your pftop.c patch. You are rounding
>
multiple times, after each scale operation. This is known
as
> rounding the intermediate results of
a calculation and degrades
> accuracy.
If you're not familiar with the issue do a Google
search
> on rounding intermediate.
>
I round
only once, that's what I've explained in my
mail.
> I suggest assigning the
pf rate to an unsigned long and multiplying by 10.
> This makes the LSD a guard digit.
> After all scaling, round once (if guard
digit >= 5 then add 10).
> Yes, this
may require one more scaling operation if it rounds up to 6
digits (including guard digit).
> At the
very end divide by 10.
> Note: This is
essentially fixed point arithmetic with one decimal
digit.
>
> I modified
pftop.c v1.37 to do this earlier today.
>
It was kind of tricky.
> I need to see if
it still looks OK on Tuesday (I'm busy Monday).
> Let me know if you want a patch then.
> I won't have actually tested it,
though, so it's highly likely to have bugs.
> You might be better off writing your own
(and then perhaps comparing to mine).
>
> RE my email client: It's Yahoo
webmail -- nothing I can do about it.
>
pftop in
systat can only display 4 digits and 1 unit symbol
so you can't display all digits of your
bandwidth spec.
But please by all means,
send your diff and I'll take a look at it.
