"Steven D'Aprano" <st...@remove-this-cybersource.com.au> wrote in message
news:4c83b425$0$28657$c3e8...@news.astraweb.com...
On Sun, 05 Sep 2010 12:28:47 +0100, BartC wrote:
It would
be nice if you could directly code low-level algorithms in it without
relying on accelerators, and not have to wait two and a half minutes (or
whatever) for a simple test to complete.
Yes, and it would be nice if my clothes washed and ironed themselves, but
they don't.
Somebody has to do the work. Are you volunteering to write the JIT
compiler for CPython? Will you contribute to the PyPy project, or help
maintain Psycho, or are you just bitching?
I've thought about it (writing an independent interpreter). But I don't know
enough of the language, and a lot of it I don't understand (eg. OOP).
Besides, I think the language itself deliberately makes it difficult to get
it up to speed. Some of the reasons might be the ones set down here, in
Chapter 2:
http://codespeak.net/svn/user/antocuni/phd/thesis/thesis.pdf
(Instead, I've confined my efforts to my own projects; the last interpreter
I worked on did in fact get within a magnitude of C in performance, without
using JIT or other fancy tricks.)
The simple fact is that there are far more important things for Python
developers to spend their time and effort on than optimizations like this.
I don't know, there's seem to be an awful lot of effort going into
addressing exactly this issue (eg. PyPy, Pscyo, Unladen Swallow,
Shedskin....)
If such an optimization comes out of the PyPy project, I'll be cheering
them on -- but it's a lot of effort for such a trivial gain.
The example given by the Original Poster is contrived. Nobody sensibly
writes an integer multiplication as a repeated addition like that, and
any real code that would need to be put in a for loop is almost certainly
going to be too complicated for the JIT compiler to benefit greatly. The
loop overhead itself will almost certainly be overwhelmed by the work
done in the loop:
OK, you're saying there's no point in reducing the loop overhead, because
the loop body is going to be even slower.
All those compilers that offer loop unrolling are therefore wasting their
time...
--
Bartc
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