Python ghcomp question

Replies to This Discussion

Permalink Reply by Aaron M. Ryan on December 26, 2013 at 10:41pm

Changing to List Access works!

Permalink Reply by Aaron M. Ryan on December 26, 2013 at 11:26pm

But...I can't get it to work if I copy Steve Baer's example and use this code:

import ghpythonlib.components as ghcomp
import ghpythonlib.parallel

#custom function that is executed by parallel.run
def Voronoi2D(point):
result = ghcomp.Voronoi(point, rect)
if result: return result.curves

if parallel:
cells = ghpythonlib.parallel.run(Voronoi2D, points, True)
else:
cells = ghcomp.Voronoi(points, rect)

a = cells

I am getting a list of Nulls when parallel is set to True...it works when set to False

Any thoughts?

AA

Permalink Reply by djordje on December 27, 2013 at 4:23am

Hi Aaron,

Apart from supplying the "rec" (rectangle) as your second argument in ghcomp.Voronoi(), whereas actual second one is cells radius and third one is boundary(your rectangle) - the problem seems to be with the very nature of how Voronoi algorithm works - it creates cells by taking a list of points and calculating intersections of their half-spaces.
Let's say you have dual-core. What you seem to do with parallel module is to provide a single point to the first cpu - which results in "None" (Null in grasshopper) as ghcomp.Voronoi() could not make a Voronoi cells diagram out of just one point. Then you pass the second point to the second cpu - same thing happens. Then you pass on the third point to the first cpu - again "None". And so on. In the end you are getting a list of "None"'s (that is "Nulls in VB.NET) which equals the number of your input points.

So basically your code will work if you would provide a list of boundaries (rectangles) as an argument of the ghpythonlib.parallel.run() function instead of list of points. In that way parallel module will take a list of all points and a single boundary and assign it to one cpu - which will produce a list of voronoi cells for that boundary. Then take the whole list of points again and second boundary and assign it to your second cpu. Etc.
Btw, I have been puzzled with this issue too.

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