[chbot] Filter

[mikael stewart]

Yes you're right. I was absorbed thinking about quantization as I was
writing and missed that double division.

Also noted a typo: filtered_value was supposed to be written as filt_value
in my original response.

Another thing to add that might be useful is to initialize the filter in
some way, such as:
filt_value = raw_value;
filt_sum = 100 * filt_value;

Or instead of basing it on one raw sample, use some nominal expected value
to get you to your settled value faster.

Mikael



On Thu, Oct 18, 2018 at 12:47 PM Volker Kuhlmann <list57 at top.geek.nz> wrote:

> > filt_sum = filt_sum - filt_sum / 100 + raw_value;
> > filt_value = filt_sum / 100;
> >
> > The second line only needs to be evaluated when you actually need to use
> > the result.
>
> Why is that an evaluation improvement?
> It's the same as
>
> filt_value = filt_sum / 100;
> filt_sum = filt_sum - filt_value + raw_value;
>
> where you can read filt_value for the filter result any time. It has the
> same number of expression statements but adds one store to filt_value
> per step. That's very cheap compared with a division.
>
> Volker
>
> --
> Volker Kuhlmann
> http://volker.top.geek.nz/      Please do not CC list postings to me.
>
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