[Dr. Geo] [Bug 1761420] Re: Rendering time of Point Morph

[Benoît St-Jean]

I played with the "Approximation of Pi" to explore a bit of Dr. Geo's
code and found a few things. I tested with 2000 points and different
preferences/options.

First thing, the TextMorphs. Another way of doing it would be to lazy
initialize #textMorph.  With the "Approximation of Pi" script right now,
setting the textMorph string to an empty string accounts for 18.9% of
the processing time, let alone all the TextMorphs it adds to the heap
and that have to be refreshed (for nothing!).  The current script, for
2000 points, created 2000 TextMorphs that end up in the UI notification
list for... nothing.

Second problem I noticed is the slowness of #doOneCycle.

When the application has to deal/refresh tons of morphs, the rendering
heap quickly accumulates 4000+ morphs (I set the limit to 2000 points to
profile it).  If we'd have a #partialDoOneCycle (for lack of a better
name), it would greatly speed things up!  It could be used in cases
where simulations generate a huge number of points.

I was able to get a 2x speedup by changing the script (last line before
the closing bracket of the block, replacing "World doOneCycle" to:

(try \\ 10) = 0 ifTrue: [World doOneCycle].

We could keep track of #doOneCycle sends in a class variable somewhere
in Geo and only refresh a certain percentage of the time (e.g. every 10
calls).  Most of the time, we wouldn't need that but in cases where you
generate *tons* of objects (usually Points), it would dramatically speed
up things.

Another thing is the initialization of DrGPointCostumeStyle instances.
The fact that the method sends 3 messages (setters) with 3 "self
changed" consumes an awful lot of time (heap list has 4000 objects for
2000 points!).  DrGPointCostumeStyle could be optimized in the
#initialize method by creating a #color:pointSize:shape setter that
would send a "self changed" only once instead of 3 times (as is the case
right now).  I have seen other cases similar to this one in the code.

Also, for some reason, the shape of the points also have an impact (I
will investigate this later).  My tests show a dramatic difference
between circle and cross points as compared to square points, a ration
of 2 to 1 !

here are the results I have collected (based on 4 tries each):

"Round point"
Milliseconds to execute script: 210455
World step list size: 4004

"Square point"
Milliseconds to execute script: 104065
World step list size: 4004

"Round point, refreshed every 10 times"
Milliseconds to execute script: 117344
World step list size: 4004

"Square point, refreshed every 10 times"
Milliseconds to execute script: 51305
World step list size: 4004

"Round point, DrGPointCostume with TextMorph initialized to nil"
Milliseconds to execute script: 115285
World step list size: 2004

"Cross point, DrGPointCostume with TextMorph initialized to nil"
Milliseconds to execute script: 114876
World step list size: 2004

"Square point, DrGPointCostume with TextMorph initialized to nil"
Milliseconds to execute script: 46316
World step list size: 2004

"Round point, DrGPointCostume with TextMorph initialized to nil, refreshed 
every 10 times"
Milliseconds to execute script: 49098
World step list size: 2004

"Cross point, DrGPointCostume with TextMorph initialized to nil, refreshed 
every 10 times"
Milliseconds to execute script: 45259
World step list size: 2004

"Square point, DrGPointCostume with TextMorph initialized to nil, refreshed 
every 10 times"
Milliseconds to execute script: 13630
World step list size: 2004

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https://bugs.launchpad.net/bugs/1761420

Title:
  Rendering time of Point Morph

Status in Dr. Geo II:
  Confirmed

Bug description:
  PointMorph are initialized with an empty label (text morph). 
  When a sketch comes with a lot of point, this emoty lable still slow down a 
lot the Athens canvas rendering.
  Solution: keep the textmorph as nil as long as there is not label attached to 
a point.

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