Calculating integral images / cumulative add

[Stefan Reich]

Oh I just saw this in the presentation
<http://cr.openjdk.java.net/~jrose/pres/201907-Vectors.pdf>:

  ▪ Segmented scan (reduce with partials and mask-driven reset)

That's probably what I want... so it's not there yet?

On Tue, 5 Jan 2021 at 02:31, Stefan Reich <
stefan.reich.maker.of.eye at googlemail.com> wrote:

> Hi,
>
> I am trying to vectorize my routine that constructs an integral image / "summed-area
> table" <https://en.wikipedia.org/wiki/Summed-area_table>.
>
>     int i = 0;
>     for (int y = 0; y < h; y++) {
>       int sum = 0;
>       for (int x = 0; x < w; x++) {
>         sum += image[i];
>         data[i] = y > 0 ? sum + data[i-w] : sum;
>         i++;
>       }
>     }
>
> In order to use the Vector API, I'd need an operation that does a
> cumulative summing over the lanes, e.g. for a 4-component vector:
>
> b[0] = a[0]
> b[1] = a[0]+a[1]
> b[2] = a[0]+a[1]+a[2]
> b[3] = a[0]+a[1]+a[2]+a[3]
>
> I don't think this is available in the current Vector API, is it?
>
> Thanks,
> Stefan
>
> --
> Stefan Reich
> BotCompany.de // Java-based operating systems
>


-- 
Stefan Reich
BotCompany.de // Java-based operating systems