Standardized interpreter speed evaluation tool

[Dave Angel]

alexru wrote:
> Is there any standardized interpreter speed evaluation tool? Say I
> made few changes in interpreter code and want to know if those changes
> made python any better, which test should I use?
>
>   
Not trying to be a smart-aleck, but the test you use should reflect your 
definition of the phrase "any better."  For example, suppose you decided 
that you could speed things up by pre-calculating a few dozen megabytes 
of data, and including that in the python.dll.  This would change the 
memory footprint of Python, and possibly the interpreter's startup/load 
time, not just the runtime of whatever loop you are testing.

But if I assume you know all that and just want to do timings.  There 
are at least two stdlib functions that can help:

import time
time.time() and time.clock() will give you a wall-clock floating point 
number, and you can subtract two of these within the same program to see 
how long something takes.  This approach ignores interpreter startup, 
and does nothing to compensate for other processes running on the 
system.  But it can be very useful, and easy to run.  The resolution on 
each function varies by OS, so you may have to experiment to see which 
one gives the most precision.

import time
start  = time.time()
dotest()
print "Elapsed time", time.time() - start

timeit module can be used within code for timing, or it may be used to 
load and run a test from the command line.  In the latter version, it 
includes the startup time for the interpreter, which might be 
important.  It also can execute the desired code repeatedly, so you can 
get some form of averaging, or amortizing.

*** python -m timeit ....

Note that due to system caching, doing multiple runs consecutively may 
give different results than ones that are separated by other programs 
running.  And of course when you recompile and link., the system buffers 
will contain an unusual set of data.  So there are ways (which I don't 
recall) of flushing the system buffers to let programs start on equal 
footing.

DaveA