On Apr 18, 2004, at 8:06 AM, Leopold Toetsch wrote:

To handle multiple files, we'll probably need to generate a .c to hold
the C strings (instead of the .h), and have an extern declaration in
the .h (since it will be included in multiple files). That's assuming
they'll all be aggregated into a single file (which makes sense).

Here is a related patch, to cause us to cache the hash values of all
strings (on demand). The important part is that the cached value is
cleared out in unmake_COW, which is called any time we might mutate the
string (and thus, invalidate the cached value). This will have the
side-effect of allowing c2str.pl to be slightly simpler, since it won't
need to pre-calculate the hash value (since const strings are the same
as any others, and their hash value will be calculated and cached if it
is ever needed).

This change speeds up the attached benchmark by a factor of 1.86 in the
optimize case (via --optimize, so -Os), or 3.73 in the unoptimized case
(on Mac OS X):

# without the patch, optimized build
% ./parrot hash-timing.pasm
679 hash entries
128 characters per test key
1000000 lookups each
rep 1:  1.093889 sec
rep 2:  1.109484 sec
rep 4:  1.095041 sec

# with the patch, optimized build
% ./parrot hash-timing.pasm
679 hash entries
128 characters per test key
1000000 lookups each
rep 1:  0.608547 sec
rep 2:  0.586352 sec
rep 4:  0.575159 sec

JEff

hash-caching.patch 5K Download

hash-timing.pasm 1K Download