python on the smalltalk VM

[Michael Hudson]

Carlos Ribeiro <cribeiro at mail.inet.com.br> writes:

> At 23:03 19/04/01 +0100, Michael Hudson wrote:
> >Douglas Alan <nessus at mit.edu> writes:
> >
> > > After many years of research, they came up with a compiler for Self
> > > that would generate code that runs about one half to one third the
> > > speed of compiled C code.  This is 30 to 50 times faster than
> > > Python.
> >
> >No it isn't.  At least, not for me.  Generally I find that fairly
> >optimized C modules are about 40-60 times faster than really optimized
> >Python (I'm better at Python than C).  Obviously "it depends", but
> >I've found these numbers to be fairly consistent over a variety of
> >tasks.
> 
> For all reasonable applications that I can think of, 30-50 compared
> to 40-60 is about the same (at least is the same order of
> magnitude). 

Doug was claiming 30-50 times faster than Python is one third to on
half the speed of C, i.e. C was 60-150 times faster than Python.

> Anyway, what really surprises me is the magnitude of the difference
> between C and Python. 

Really?  It always surprises me how small it is.

> It does make sense to have a big difference - interpreted languages
> will always be slower - but the higher level of abstraction in
> Python should allow for a smaller difference. 

But that would require a seriously smart comiler to take advantage of
the higher abstraction, no?

It would probably be the case that as you rewrite larger portions of
your code in C, the difference would get smaller - the numbers I am
talking about are for rewriting fairly simple, tightly specified
functions with little dynamism.

> It brings the question: how are these numbers measured?

In my case, by identifying hot spots in my code, trying to optimize
the snot out them in Python, rewriting them in C and them timing the
difference between my fastest C version and my fastest Python version.

> For some applications (such as text file processing) I doubt that
> the difference could be so big, specially if you know how to
> optimize your Python code.

I suspect that the main speed up for rewriting string bashing code in
C is from being able to avoid allocating memory.  This is just a hunch
though, and given that it's about performance, it's almost certainly
wrong.

Cheers,
M.

-- 
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