[Pixman] [PATCH 06/15] pixman-filter: reduced number of samples in Simpson's integration

[Oded Gabbay]

On Fri, Dec 18, 2015 at 12:17 AM, Bill Spitzak <spitzak at gmail.com> wrote:
> Ok to squash them together. Do you want me to do that?
>
Yes. There will definitely v7 of the patchset (which most likely will
be the version getting merged into the tree), so do it in that
version.

Oded

> It actually does not increase the runtime, because the two loops are only
> adding every *other* sample. Thus the same number of samples are computed.
>

> On Thu, Dec 17, 2015 at 1:23 PM, Oded Gabbay <oded.gabbay at gmail.com> wrote:
>>
>> On Sat, Dec 12, 2015 at 8:06 PM,  <spitzak at gmail.com> wrote:
>> > From: Bill Spitzak <spitzak at gmail.com>
>> >
>> > With the cubic fix this is plenty accurate enough, far in excess of the
>> > pixman
>> > fixed-point error limit. Likely even 16 samples is too many.
>> > ---
>> >  pixman/pixman-filter.c | 2 +-
>> >  1 file changed, 1 insertion(+), 1 deletion(-)
>> >
>> > diff --git a/pixman/pixman-filter.c b/pixman/pixman-filter.c
>> > index 7c1da0d..4aafa51 100644
>> > --- a/pixman/pixman-filter.c
>> > +++ b/pixman/pixman-filter.c
>> > @@ -190,7 +190,7 @@ integral (pixman_kernel_t reconstruct, double x1,
>> >      else
>> >      {
>> >         /* Integration via Simpson's rule */
>> > -#define N_SEGMENTS 128
>> > +#define N_SEGMENTS 16
>> >  #define SAMPLE(a1, a2)
>> > \
>> >         (filters[reconstruct].func ((a1)) * filters[sample].func ((a2) /
>> > scale))
>> >
>> > --
>> > 1.9.1
>> >
>> > _______________________________________________
>> > Pixman mailing list
>> > Pixman at lists.freedesktop.org
>> > http://lists.freedesktop.org/mailman/listinfo/pixman
>>
>> I think it is better to just squash this patch into the previous one,
>> as it closely related and actually makes more sense to put them
>> together so we can see the run time hasn't increased but actually
>> decreased.
>>
>>       Oded
>
>