[pygame] fast sqrt? and profiling

[Jake b <ninmonkeys@xxxxxxxxx>]

I'm writing a prototype, where I want a bunch of 'blobs', that clump/swarm, yet seperate. ( they keep min distance from each other, they don't overlap ( or at least don't stay) )

What I am doing, is every 250ms calculate each units neighbors. ( then, every loop, move away from each cached neighbor. ) My FPS stays around 26-30 until I get 62+ units, then it drops like a stone.  [ every Unit() waits 250 for its update, I calc just it, not all Units. ]

From profiling ( and testing ) I know the function to calculate locals ( neighbors ) is causing most of the slowdown.

1) Is there a suggested fast sqrt module thats portable?

2) Is it bad to use isinstance in CPU intensive loops? ( ie: function list_type() )

3) it looks like euclid.Vector2.__sub__ is taking a lot of time. Is this abnormally high? or expected? Meaning should I be using a different lib for speed? [ that particular function uses isinstance() ]

4) Do you have some useful profile queries you've found?

5) Should I be staggering the dist() calls among multiple game updates()? [ sort of am indirectly, but no enforcement. ] Or decouple physics from graphics ?

Heres the functions I mentioned above:

def calc_local(self):
        """re-calc 'who are my neighbors' to cache for later."""
        l = [] #first, get list of neighbors
        
        for u in self.game.units.list_type(Unit):
            if u == self: continue # don't collide self.
            if collide_circle( self.loc, u.loc, self.rad+self.local, u.rad):
                l.append(u)                
        self.local_cache = l

def list_type(self, t):
        """get list of units by class type. example: .list_type(Unit)"""        
        l = []
        for u in self.units:
            if isinstance(u, t): l.append(u)            

Here's the profiling I'm basing this on:
profile output: ( query = "p.sort_stats('time').print_stats(10)" )

  Ordered by: internal time
  List reduced from 311 to 10 due to restriction <10>

  ncalls  tottime  percall  cumtime  percall filename:lineno(function)
     388    2.652    0.007    2.652    0.007 {built-in method tick}
    1446    1.185    0.001    3.656    0.003 main.py:151(calc_local)
   98318    0.790    0.000    1.242    0.000 C:\Python25\lib\euclid.py:172(__sub__)
   80355    0.538    0.000    2.071    0.000 C:\jake_root\data\py\jake_includes\jakelib\util.py:49(dist)
     194    0.520    0.003    0.520    0.003 {pygame.display.flip}
   98583    0.497    0.000    0.681    0.000 C:\Python25\lib\euclid.py:243(__abs__)
   80355    0.391    0.000    2.462    0.000 C:\jake_root\data\py\jake_includes\jakelib\util.py:70(collide_circle)
  147359    0.348    0.000    0.348    0.000 {isinstance}
  147253    0.338    0.000    0.338    0.000 C:\Python25\lib\euclid.py:90(__init__)
   12175    0.288    0.000    0.694    0.000 C:\Python25\lib\warnings.py:24(warn)


I know its a lot of questions, that's why I numbered it to simplify replies. Thanks for the help.
-- 
Jake