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What is the fastest way to call Dictionary.TryGetValue ?
f#

If I have (dict: Dictionary <int, int>) and want to find a value for a given (key: int) there are three possible ways:
1.
let mutable res = 0
if dict.TryGetValue (key, &res)
then // do something with res

2.
let res = ref 0

if dict.TryGetValue (key, res)

then // do something with !res

3.
let is_found, res = dict.TryGetValue (key)

if is_found then // do something with res

Assuming the program makes very heavy use of Dictionaries, what is the fastest method? I guess (3) is the slowest by far since a tuple needs to be allocated in the process.

.

The third way is much more comfortable to use. I suggest to request optimization of it into the same IL the first one produces.

By on 5/31/2009 11:55 PM ()

The first way generates about half the amount of IL as the third way. Both 2 and 3 have a newobj. I'd wager that #1 will likely be the fastest. There's probably not _too_ much difference between 2 and 3. But, you'd have to benchmark on your target platform and runtime to make sure.

By on 5/31/2009 7:22 PM ()

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