Using a global array instead of a local one, any performance difference?

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1

Take this code for example: https://play.crystal-lang.org/#/r/75ou

SuffixArray = ["i_atk_speed", "gfiuorhng", "ierojt", "20 more mods listed here in this array"]
PrefixArray = ["i_phys", "gfiuorhng", "ierojt", "20 more mods listed here in this array"]

GlobalModArray = SuffixArray + PrefixArray


def roll_mods()
  mods_to_roll = SuffixArray + PrefixArray
  pp mods_to_roll
end


roll_mods

Is there any performance difference between mods_to_roll (creating a new local variable each time roll_mods is called), and GlobalModArray?

Using GlobalModArray inside roll_mods is the correct way to do this, right? Unless I need mods_to_roll to be mutable, correct?

If I use GlobalModArray, I won’t have have to create a local variable and append both arrays. Since that was already done when the app started, that array is now in memory. Thus, it’s faster to access?

2

GlobalArray, like any constant, is computed once. If you use a local variable it will be computed each time you call that method. So using GlobalArray is definitely faster.

1 Like
3

Good to know!! I like that, and just thought of that when creating my method.

Especially when the Suffix and Prefix lists will become very large. I can just compute them once when the app starts and select a random key based on their list size, instead of shuffling all of them all the time!

4

Also, I think you should use tuple instead of array.

Tuples are handled at compile time.