Dan Sugalski <[EMAIL PROTECTED]> writes:
>> > substr($foo, 233253, 14)
>> >
>> > is going to cost significantly more with variable sized characters than
>> > fixed sized ones.
>>
>>I don't believe so.
>
>Then you would be incorrect. To find the character at position 233253 in a
>variable-length encoding requires scanning the string from the beginning,
>and has a rather significant potential cost. You've got a test for every
>character up to that point with a potential branch or two on each one.
>You're guaranteed to blow the heck out of your processor's D-cache, since
>you've just waded through between 200 and 800K of data that's essentially
>meaningless for the operation in question.
If you are really doing that sort of processing then it would be better
to represent the data differently - say as a tree, or a list of 1000-ish char
blocks. That way you can find the block quickly and then do short-ish
search for actual chracter. (Like a text editor does.)
--
Nick Ing-Simmons
