Re: PATCH: speed up GR_UnixPangoGraphics::shape()

On Tue, 2009-07-14 at 17:16 +0100, Tomas Frydrych wrote:
> Hi Robert,
>
> Robert Wilhelm wrote:
> > Hello Tomas,
> >
> > this patch is in reply to
> > http://www.abisource.com/mailinglists/abiword-dev/2006/Feb/0081.html
> >
> > Some things take a while...
>
> :) Probably about as long since I have contributed anything ...
>
> > It avoids quadratic behavior and many calls to g_utf8_pointer_to_offset
> > by iterating only one time through the string.
>
> The patch looks good; getting rid of the g_utf8_pointer_to_offset() in
> this case makes sense, I think (though I do not see how this change
> avoids quadratic behaviour, as the while loop is equivalent of the
> g_utf8_pointer_to_offset() function call).
>
> Tomas
Hi Tomas,

thanks for the review.

                for(int i = 0; i < pGlyphs->num_glyphs; ++i)
                {
                        int iOff = pGlyphs->log_clusters[i];
- pLogOffsets[i] = g_utf8_pointer_to_offset
(pUtf8, pUtf8 + iOff);
+ while (s < pUtf8 + iOff)
+ {
+ s = g_utf8_next_char (s);
+ offset++;
+ }
+ pLogOffsets[i] = offset;
                }
        }
The point is that we remember s and offset between the iterations of
outer for loop. Therefore inner while loop is very short.

Before the inner while loop always went from pUtf8 till pUtf8+iOff.

For my testcase (first doc from #9411), we are now down to 42s from
50s.

Best regards,
row
Received on Tue Jul 14 21:12:31 2009