An Optimization Anecdote

The other day, a friend asked me a seemingly simple question: what's the best way to convert a list of integers into a string, presuming that the integers are ASCII values. For instance, the list [97, 98, 99] should be converted to the string 'abc'. Let's assume we want to write a function to do this.

via www.python.org

This exercise in optimization (in Python) is pretty fascinating (via fold).

Just for fun, I rewrote most of the functions in Perl (you can check my work in this gist); the results are actually somewhat interesting (f1() is very fast in Perl, for instance, while it's one of the slower implementations in Python). The results, using a 256-item list:

f3   6950/s    --  -21%  -50%  -74%  -98%
f6   8839/s   27%    --  -37%  -67%  -98%
f2  14023/s  102%   59%    --  -48%  -97%
f1  26920/s  287%  205%   92%    --  -94%
f7 421642/s 5967% 4670% 2907% 1466%    --

The fastest in both languages is probably the one you'd expect; in Perl, it's using pack, which is hugely faster than anything else.

Comments

[Sam Kimbrel]

Nice, but it looks like f7 in both Perl and Python only works properly if you assume a character is exactly one byte!

[Sam Kimbrel]

Also, I can't read. Looks like the exercise made that assumption.