Hi, all,
Whilst looking at some code, I noticed that a computation was being
repeated on each call, although the inputs to the computation never
changed (these were values used to define an instance of a class). I
decided to cache the value and return it rather than recomputing it.
To see the effects I ran "%timeit" on the function before and after.
I was surprised to find that the 'cached' version ran some 50 times
slower than the direct computation (in my case, 300 microseconds vs. 6
microseconds).
I traced the cached version to see what was causing the time
increase. The code is
def blah(self):
# self.val is initialized to 'None' when the class is
instantiated.
if self.val == None:
self.val = arithmetic_expression
return self.val
The first time through, control passes through the computation and
returns the value (after storing it). The second time through, the
"traced" execution goes wandering off into the weeds, starting with
/SandBox/Justin/sb/sage/local/lib/python2.5/
traceback.py(232)format_exc()
and ending up in getline() before I get bored and quit. If I step
through this, using "return" all the way, execution just terminates
back at the sage prompt, with no output.
I can't tell if this is just an artifact of some funky debugging
interaction (am I debugging the debugger?), or whether this is really
where the code goes.
Anyone have a clue to spare? Something I'm missing?
Justin
--
Justin C. Walker, Curmudgeon-At-Large, Director
Institute for the Enhancement of the Director's Income
--------
The path of least resistance:
it's not just for electricity any more.
--------
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