Dictionary vs Object

Recently I was wondering about different between using Object and Dictionary. One of the biggest pros about using Dictionary is possibility to use weak reference in key. This mechanism do not create an obstacles during Garbage Collection. Important fact is that weak references is quite expensive for collecting process, there is impact on overhead.

I have crated some test to show differences between Objects and Dictionaries.

Setup

compiler: AIR SDK 4.0
compiler mode: Release
flash player standalone: 11.9 Debug
sources: github

Each test was repeated 10 times and after that average time has been computed.

Test memory consuming

Objects
– cost of instance: 40B
– cost of key: 16B

Dictionary
– cost of instance: 56B
– cost of key: 16B

Tests Performance

Create instaces

Put values

Get values

Delete keys

 

Delete keys is most expensive operation on Hashtables. I recommend to use assign null instead removing keys (if this is possible) and then check that value over key is not null. From time to time it should be more optimal to make a cleanup and create new – clean hashtable.

Loop: for in

Loop: for each

 

This element is interesting, for each statement is 6 times faster that for in. But sometimes key is very important. My advice is that to save key inside value object.

Summary

• avoid to delete keys from Dictionary and Objects
• Dictionary is more memory consuming
• Dictionary with weak reference increment Garbage Collector overhead
• There is no big difference between putting and getting values between Dictionary and Object
• It is faster to create Objects by {}
• for each loop is faster than for in