Re: Instance vars, local vars and speed
Re: Instance vars, local vars and speed
- Subject: Re: Instance vars, local vars and speed
- From: Jean-Daniel Dupas <email@hidden>
- Date: Mon, 4 Aug 2008 14:51:36 +0200
Le 4 août 08 à 13:26, Trygve Inda a écrit :
I am transitioning some code from Carbon to Cocoa and redesigning a
lot of
how things work. I am doing a bit of low-level pixel manipulation and
wondering about speed of access to variables declared in a method vs
those
declared at the object level.
Obviously things like x,y loop counters are local to a method, but
some
things need to be shared between methods and rather then passing
values
around, it would be cleaner to declare these at the object level.
How much of a hit am I going to take?
Would it be best to declare them at the object level and copy it
into a
local as needed... Will the compiler be smart enough to sort this out?
Will it ever put object (instance) variables in a register?
I know it may require real world testing, but it affects my overall
design
too. Note that it could be going through a loop roughly 3 million
times on a
large image.
Many thanks,
Trygve
IMHO, this is just premature optimisation.
That said, there is no cost to access an ivar using the 32 bits
runtime, and I don't think the cost on 64 bits runtime is important
enough to bother with it.
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