Speed Comparison Perl Python & C

Neil Hodgson nhodgson at bigpond.net.au
Tue Mar 2 21:52:55 CET 2004

beliavsky at aol.com:

> Thanks. I am going to learn about Psyco. In this case, I assume that
> doing the computations with floating point numbers and finally
> converting the result to int gives the same values as the original
> integer calculation. In other cases, integer arithmetic will need to
> be done with integers to ensure correct results.

   Yes, in this case float has enough range. That is something you get to
determine with any fixed length numeric representation.

> Python is supposed to be easy (and in general I agree that it is), but
> your solution requires some knowledge of
> (1) how integer and floating point calculations are done (which many
> novices do not have)
> (2) when Psycho can speed things up
> and the final result is still much slower than Fortran. For the
> Fortran program, the only "trick" is the use of integer*8.

   With Fortran, you need to know how large your values are going to become.
If you increased the number of iterations in your example sufficiently,
Fortran's 64 bit integers would overflow requiring understanding of the
concept of fixed range integers. Python avoids this by using unbounded
integers. Python is oriented towards ease of use and correctness at the
expense of speed. If the speed of the Python program is inadequate then you
can take a working Python program and work on its speed. Or decide that the
speed problem needs another language.

   Python does optimize integers that can be represented in 32 bits but
larger than that and unbounded integers are used. For some applications, it
would be better if Python also optimized integers that require between 32
and 64 bits.


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