Would there be difference in speed between
if (myInt == CONST_STATE1)
and
if (myEnum == myENUM.State1)
in c#?
views:
299answers:
3
+7
A:
In C# Enums are in-lined to be constants by the compilier anyway, so the benefit is code legibility
Rowland Shaw
2009-01-02 12:47:05
Perfect. That actually answers quite a few other questions i had! +1
Adam Naylor
2009-01-02 12:47:56
You don't happen to know the datatype of such a constant?
Adam Naylor
2009-01-02 12:48:52
And even if there was a difference it would rarely if ever be significant.
Brian Rasmussen
2009-01-02 12:49:21
@Brian how about in 3D calculations?
Adam Naylor
2009-01-02 12:50:15
The datatype? Its underlying type is an int32 by default, if that's what you mean.
jalf
2009-01-02 12:50:41
There's nothing magical about 3d calculations. Why would it be more expensive there?
jalf
2009-01-02 12:51:33
@Adam: even for 3d calculations I doubt that you'll be spending a significant amount of time doing these comparisons. If these ifs add up to say 1% of the time, you'll not gain a lot by making it go a little faster.
Brian Rasmussen
2009-01-02 12:58:08
@jalf - um, because expense is directly proportional to the number of times an operation runs. Do I need to explain the operation count in even a basic 3D simulation? – Adam Naylor (0 secs ago) [remove this comment]
Adam Naylor
2009-01-02 13:01:16
Well, it's exactly the same performance. myEnum == myENUM.State1 is translated to int comparison by the JIT. Also, if your enum has fewer options you can change its underlying type to byte or short, and use a smaller data type which usually yields better performance.
configurator
2009-01-02 15:52:21
+1
A:
Also, I'm not sure you need to be worried about this at all. It does sound like premature optimisation. I'm sure that in any system, there are bigger bottlenecks than enum comparisons. :)
Ray Booysen
2009-01-03 10:42:03
+1
A:
The thing to be careful about when using Enums is not to use any of the operations that require reflection (or use them with care). For example:
- myEnumValue.ToString().
- Enum.Parse()
- Enum.IsDefined()
- Enum.GetName()
- Enum.GetNames()
In case of constants the option of doing any operations that require reflection doesn't exist. However, in case of enums it does. So you will have to be careful with this.
I have seen profile reports where operations relating to enum validations / reflections took up to 5% of the CPU time (a scenario where enum validations were done on every call to an API method). This can be greatly reduced by writing a class that caches the results of the reflection of the enum types being used.
Having said that, I would recommend making the decision of using enum vs. constant based on what makes sense from a design point of view. This is while making sure that the team is aware of the performance implications of the operations involving reflection.
vboctor
2009-01-03 11:04:47