doubling the number of tests, but not taking twice as long

Tue Jul 17 02:59:22 EDT 2018

Larry Martell wrote:
> I had some code that did this:
>> meas_regex = '_M\d+_'
> meas_re = re.compile(meas_regex)
>> if meas_re.search(filename):
> stuff1()
> else:
> stuff2()
>> I then had to change it to this:
>> if meas_re.search(filename):
> if 'MeasDisplay' in filename:
> stuff1a()
> else:
> stuff1()
> else:
> if 'PatternFov' in filename:
> stuff2a()
> else:
> stuff2()
>> This code needs to process many tens of 1000's of files, and it runs
> often, so it needs to run very fast. Needless to say, my change has
> made it take 2x as long. 

That is *not* self-evident. Usually stuffX() would take much longer than the 
initial tests.
So the first step would be to verify that
if meas_re.search(filename):
 if 'MeasDisplay' in filename:
 pass
 else:
 pass
else:
 if 'PatternFov' in filename:
 pass
 else:
 pass
takes a significant amount of the total time the piece of code you give 
takes to execute.
> Can anyone see a way to improve that?

Not really. I'd check if there is a branch that is executed most of the time 
or that takes much longer to execute than the other ones, and then try to 
optimize that.