On Nov 10, 2008, at 2:32 PM, Stan Vassilev | FM wrote:
I just ran a quick benchmark on this and I'm not seeing a
significant real world change for Facebook's codebase. (definitely
less than 1%) This was a pretty small test, without a lot of code
execution, so I could see other applications doing better. I'm
pretty neutral on this one, it's not a really big change so might
be worth adding if it's going to give a few applications out there
a gain, but I couldn't see doing this everywhere of course.
-shire
Hi,
Something that could give arrays a boost would be to:
- pool all string literals in each file
- give each stringl iteral an id (unique in the loaded environment)
- bind early all array access with string literals (a common
occurence), so they don't need to be resolved with a hashmap lookup,
but rather, a direct stirng literal id lookup.
The benefit of this approach are:
- There's no need to generate a hashmap in the first place
- String literal id-s are unique integers and have no conflicts, so
no need to do conflict resolution.
This wouldn't really help with the case here of "if ($array1 ==
$array2)..." though right? (not to say it's not good, just making
sure I understand ;-) ).
It sounds like this would only work if the array contents where static
though, as you're mapping a constant string to the contents of the
hash (or did I misunderstand and you'd be mapping string const. values
to hash IDs?).
I am at the point now where my #1 item CPU wise is my hash function.
I'm working on finding a slightly faster implementation, but I'm also
playing with having a hash value stored in every zval so that the hash
function call can be skipped if we've already ran it once. The
problem that comes into play here is that there's no central code to
update or clear the hash if the string or contents of the zval
change. Of course, doing this with constant values would be easier to
accomplish and could be done at compile time, and like you say this is
a pretty common scenario.
-shire
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