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Instance vars, local vars and speed
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Instance vars, local vars and speed


  • Subject: Instance vars, local vars and speed
  • From: Trygve Inda <email@hidden>
  • Date: Mon, 04 Aug 2008 11:26:11 +0000
  • Thread-topic: Instance vars, local vars and speed

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


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