Is there a difference in performance between 'const' and 'var' declarations in Roslyn?
In a .NET application, there's a definitive performance difference between these two ways of declaring a string value:
const string MyConst = "value";var MyConst = "value";
The former (#1) is a compile-time declaration so there is no performance loss at runtime, compared to the latter (#2) which will allocate and initialize a String object every time that line of code is executed.
In my project I utilize Roslyn to compile user-specified C# scripts using CSharpCodeProvider.CompileAssemblyFromSource, extract the relevant methods (MethodInfo objects) and keep them around in memory to be invoked later as needed.
My question is, do the aforementioned performance differences still apply in this case? Are const, static and other statements that are normally compile-time, still behave in that fashion when a script is compiled and executed in-memory, as described above?
c# .net performance roslyn
asked Nov 15 '18 at 20:18
taiji123taiji123
150210
add a comment |
In a .NET application, there's a definitive performance difference between these two ways of declaring a string value:
const string MyConst = "value";var MyConst = "value";
The former (#1) is a compile-time declaration so there is no performance loss at runtime, compared to the latter (#2) which will allocate and initialize a String object every time that line of code is executed.
In my project I utilize Roslyn to compile user-specified C# scripts using CSharpCodeProvider.CompileAssemblyFromSource, extract the relevant methods (MethodInfo objects) and keep them around in memory to be invoked later as needed.
My question is, do the aforementioned performance differences still apply in this case? Are const, static and other statements that are normally compile-time, still behave in that fashion when a script is compiled and executed in-memory, as described above?
c# .net performance roslyn
asked Nov 15 '18 at 20:18
taiji123taiji123
150210
3
Strings are interned. I doubt you will see any meaningful difference.
– Robert Harvey♦
Nov 15 '18 at 20:20
Are you interested inconstgenerally? Orconst stringspecifically?
– mjwills
Nov 15 '18 at 20:22
@mjwills, I was thinking generally, but didn't realize there was a qualitative difference/something special about 'const string' as opposed to 'const anything-else'...?
– taiji123
Nov 15 '18 at 20:32
1
The main 'downside' ofconstgenerally is that the the value gets inlined whenever used - stackoverflow.com/questions/24227690/… . This can mean your final binaries are larger than if you didn't useconst. In practice, you are incredibly unlikely to experience issues due to this.
– mjwills
Nov 15 '18 at 20:35
1
It makes no difference. You have to use the const somewhere, it will look like var something = MyConst; Which is exactly the same as the 2nd statement. The metadata is a wee bigger for the 1st statement since it has to store the const definition, the perf deterioration due to the less efficient usage of VM is not measurable.
– Hans Passant
Nov 15 '18 at 22:31
add a comment |
In a .NET application, there's a definitive performance difference between these two ways of declaring a string value:
const string MyConst = "value";var MyConst = "value";
The former (#1) is a compile-time declaration so there is no performance loss at runtime, compared to the latter (#2) which will allocate and initialize a String object every time that line of code is executed.
In my project I utilize Roslyn to compile user-specified C# scripts using CSharpCodeProvider.CompileAssemblyFromSource, extract the relevant methods (MethodInfo objects) and keep them around in memory to be invoked later as needed.
My question is, do the aforementioned performance differences still apply in this case? Are const, static and other statements that are normally compile-time, still behave in that fashion when a script is compiled and executed in-memory, as described above?
c# .net performance roslyn
asked Nov 15 '18 at 20:18
taiji123taiji123
150210
In a .NET application, there's a definitive performance difference between these two ways of declaring a string value:
const string MyConst = "value";var MyConst = "value";
The former (#1) is a compile-time declaration so there is no performance loss at runtime, compared to the latter (#2) which will allocate and initialize a String object every time that line of code is executed.
In my project I utilize Roslyn to compile user-specified C# scripts using CSharpCodeProvider.CompileAssemblyFromSource, extract the relevant methods (MethodInfo objects) and keep them around in memory to be invoked later as needed.
My question is, do the aforementioned performance differences still apply in this case? Are const, static and other statements that are normally compile-time, still behave in that fashion when a script is compiled and executed in-memory, as described above?
c# .net performance roslyn
c# .net performance roslyn
asked Nov 15 '18 at 20:18
taiji123taiji123
150210
asked Nov 15 '18 at 20:18
taiji123taiji123
150210
asked Nov 15 '18 at 20:18
taiji123taiji123
150210
asked Nov 15 '18 at 20:18
taiji123taiji123
150210
asked Nov 15 '18 at 20:18
taiji123taiji123
150210
150210
3
Strings are interned. I doubt you will see any meaningful difference.
– Robert Harvey♦
Nov 15 '18 at 20:20
Are you interested inconstgenerally? Orconst stringspecifically?
– mjwills
Nov 15 '18 at 20:22
@mjwills, I was thinking generally, but didn't realize there was a qualitative difference/something special about 'const string' as opposed to 'const anything-else'...?
– taiji123
Nov 15 '18 at 20:32
1
The main 'downside' ofconstgenerally is that the the value gets inlined whenever used - stackoverflow.com/questions/24227690/… . This can mean your final binaries are larger than if you didn't useconst. In practice, you are incredibly unlikely to experience issues due to this.
– mjwills
Nov 15 '18 at 20:35
1
It makes no difference. You have to use the const somewhere, it will look like var something = MyConst; Which is exactly the same as the 2nd statement. The metadata is a wee bigger for the 1st statement since it has to store the const definition, the perf deterioration due to the less efficient usage of VM is not measurable.
– Hans Passant
Nov 15 '18 at 22:31
add a comment |
3
Strings are interned. I doubt you will see any meaningful difference.
– Robert Harvey♦
Nov 15 '18 at 20:20
Are you interested inconstgenerally? Orconst stringspecifically?
– mjwills
Nov 15 '18 at 20:22
@mjwills, I was thinking generally, but didn't realize there was a qualitative difference/something special about 'const string' as opposed to 'const anything-else'...?
– taiji123
Nov 15 '18 at 20:32
1
The main 'downside' ofconstgenerally is that the the value gets inlined whenever used - stackoverflow.com/questions/24227690/… . This can mean your final binaries are larger than if you didn't useconst. In practice, you are incredibly unlikely to experience issues due to this.
– mjwills
Nov 15 '18 at 20:35
1
It makes no difference. You have to use the const somewhere, it will look like var something = MyConst; Which is exactly the same as the 2nd statement. The metadata is a wee bigger for the 1st statement since it has to store the const definition, the perf deterioration due to the less efficient usage of VM is not measurable.
– Hans Passant
Nov 15 '18 at 22:31
3
3
Strings are interned. I doubt you will see any meaningful difference.
– Robert Harvey♦
Nov 15 '18 at 20:20
Strings are interned. I doubt you will see any meaningful difference.
– Robert Harvey♦
Nov 15 '18 at 20:20
Are you interested in
const generally? Or const string specifically?– mjwills
Nov 15 '18 at 20:22
Are you interested in
const generally? Or const string specifically?– mjwills
Nov 15 '18 at 20:22
@mjwills, I was thinking generally, but didn't realize there was a qualitative difference/something special about 'const string' as opposed to 'const anything-else'...?
– taiji123
Nov 15 '18 at 20:32
@mjwills, I was thinking generally, but didn't realize there was a qualitative difference/something special about 'const string' as opposed to 'const anything-else'...?
– taiji123
Nov 15 '18 at 20:32
1
1
The main 'downside' of
const generally is that the the value gets inlined whenever used - stackoverflow.com/questions/24227690/… . This can mean your final binaries are larger than if you didn't use const. In practice, you are incredibly unlikely to experience issues due to this.– mjwills
Nov 15 '18 at 20:35
The main 'downside' of
const generally is that the the value gets inlined whenever used - stackoverflow.com/questions/24227690/… . This can mean your final binaries are larger than if you didn't use const. In practice, you are incredibly unlikely to experience issues due to this.– mjwills
Nov 15 '18 at 20:35
1
1
It makes no difference. You have to use the const somewhere, it will look like var something = MyConst; Which is exactly the same as the 2nd statement. The metadata is a wee bigger for the 1st statement since it has to store the const definition, the perf deterioration due to the less efficient usage of VM is not measurable.
– Hans Passant
Nov 15 '18 at 22:31
It makes no difference. You have to use the const somewhere, it will look like var something = MyConst; Which is exactly the same as the 2nd statement. The metadata is a wee bigger for the 1st statement since it has to store the const definition, the perf deterioration due to the less efficient usage of VM is not measurable.
– Hans Passant
Nov 15 '18 at 22:31
add a comment |
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3
Strings are interned. I doubt you will see any meaningful difference.
– Robert Harvey♦
Nov 15 '18 at 20:20
Are you interested in
constgenerally? Orconst stringspecifically?– mjwills
Nov 15 '18 at 20:22
@mjwills, I was thinking generally, but didn't realize there was a qualitative difference/something special about 'const string' as opposed to 'const anything-else'...?
– taiji123
Nov 15 '18 at 20:32
1
The main 'downside' of
constgenerally is that the the value gets inlined whenever used - stackoverflow.com/questions/24227690/… . This can mean your final binaries are larger than if you didn't useconst. In practice, you are incredibly unlikely to experience issues due to this.– mjwills
Nov 15 '18 at 20:35
1
It makes no difference. You have to use the const somewhere, it will look like var something = MyConst; Which is exactly the same as the 2nd statement. The metadata is a wee bigger for the 1st statement since it has to store the const definition, the perf deterioration due to the less efficient usage of VM is not measurable.
– Hans Passant
Nov 15 '18 at 22:31