Tim,
I couldn't resist; here is a numerix version of the method, which I
committed to svn:
def get_transformed_patches(self):
# Shouldn't need all these calls to asarray;
# the variables should be converted when stored.
# Similar speedups with numerix should be attainable
# in many other places.
verts = asarray(self._verts)
offsets = asarray(self._offsets)
Npoly = len(offsets)
scales = sqrt(asarray(self._sizes)*self._dpi.get()/72.0)
Nscales = len(scales)
if Nscales >1:
scales = resize(scales, (Npoly, 1, 1))
transOffset = self.get_transoffset()
xyo = transOffset.numerix_xy(offsets)
polys = scales * verts + xyo[:, newaxis, :]
return polys
It is faster even when there are only three polygons; and as the comment
indicates, it would be even faster with additional numpification of the
entire class. (Present version with 3 polys, 161 usecs vs 241 usecs;
with 1000, 6.4 msec vs 47.3 msec.)
It is also only lightly tested. I hope I haven't overlooked some
situation that would work with the old version but not with this one.
Eric
Tim Leslie wrote:
> On 5/10/07, Eric Firing <[EMAIL PROTECTED]> wrote:
>> Tim,
>>
>> Based on a *very superficial* quick look, I have two comments:
>>
>> 1) Since the plan is (or was?) to have one more release before
>> specializing to numpy-only support, the ".T" won't work at present.
>>
>> 2) In the following (possibly mangled by mailer),
>>
>> > + if Nsizes == 1:
>> > + xy = asarray([xverts, yverts]).T * sizes[0]
>> > + polys = [xy + offset for offset in
>> transOffset.seq_xy_tups(self._offsets)]
>>
>> I think you can gain additional speedup by eliminating the list
>> comprehension. Instead of using seq_xy_tups you can use numerix_xy to
>> return a 2-D array (with columns x and y), and simply add that to xy.
>>
>
> Thanks for the feedback Eric, I'll rework the patch with your comments
> in mind. I also just noticed a rather glaring bug, in that I don't
> actually have a 'return polys' after I calculate them in the special
> case, which is somewhat embarrassing. I'll fix all this up and submit
> a new patch later today.
>
> Cheers,
>
> Tim
>
>> Eric
>>
>>
>> Tim Leslie wrote:
>> > Hi All,
>> >
>> > I've attached a patch which optimizes a particular case of the
>> > RegularPolyCollection.get_transformed_patches method. This is
>> > particularly useful when using a picker on a scatter plot with ~40,000
>> > points (as I happen to be doing) and cuts the time spent in this
>> > function from ~4s to ~1s, which accounts for about 50% of the lag in
>> > my particular use case.
>> >
>> > Similar improvements might be possible in the N > 1 case, but I don't
>> > have a) a data set or b) the time to work them out with, so hopefully
>> > someone is happy to check in this patch as it stands, as I think the
>> > N==1 is probably the common case.
>> >
>> > If there are any problems with the patch let me know and I'll try to
>> > fix it up. It's against latest svn (3262)
>> >
>> > Cheers,
>> >
>> > Tim
>> >
>> >
>> >
>> ------------------------------------------------------------------------
>> >
>> > Index: lib/matplotlib/collections.py
>> > ===================================================================
>> > --- lib/matplotlib/collections.py (revision 3262)
>> > +++ lib/matplotlib/collections.py (working copy)
>> > @@ -153,7 +153,7 @@
>> > if not self.pickable(): return
>> > ind = []
>> > x, y = mouseevent.x, mouseevent.y
>> > - for i, thispoly in enumerate(self.get_transformed_patches()):
>> > + for i, thispoly in enumerate(self.get_transformed_patches()):
>> > inside = nxutils.pnpoly(x, y, thispoly)
>> > if inside: ind.append(i)
>> > if len(ind):
>> > @@ -167,7 +167,6 @@
>> > The ith element in the returned sequence is a list of x,y
>> > vertices defining the ith polygon
>> > """
>> > -
>> > verts = self._verts
>> > offsets = self._offsets
>> > usingOffsets = offsets is not None
>> > @@ -451,13 +450,19 @@
>> > __init__.__doc__ = dedent(__init__.__doc__) % kwdocd
>> >
>> > def get_transformed_patches(self):
>> > -
>> > +
>> > xverts, yverts = zip(*self._verts)
>> > xverts = asarray(xverts)
>> > yverts = asarray(yverts)
>> > sizes = sqrt(asarray(self._sizes)*self._dpi.get()/72.0)
>> > Nsizes = len(sizes)
>> > transOffset = self.get_transoffset()
>> > +
>> > + # optimize this case for an approx 4x speedup
>> > + if Nsizes == 1:
>> > + xy = asarray([xverts, yverts]).T * sizes[0]
>> > + polys = [xy + offset for offset in
>> transOffset.seq_xy_tups(self._offsets)]
>> > +
>> > polys = []
>> > for i, loc in enumerate(self._offsets):
>> > xo,yo = transOffset.xy_tup(loc)
>> >
>> >
>> >
>> ------------------------------------------------------------------------
>> >
>> >
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