Extending dynamic sorting of objects using lightweight code generation.
UPDATE: This project is hosted on CodePlex as the Dynamic Reflection Library for all further updates.
RE: Dynamic sorting of objects using lightweight code generation.
I got a report of issues sorting objects that have null (not Nullable<T>) values. In the previous implementation, I blindly call down to the CompareTo method associated with the property's Type. This obviously doesn't work with virtual methods. For some types (like String) it was enough to simply make the emitted code a Call instead of a CallVirt, but I didn't want to be half-right. So the new version does the right thing and handles the null-checks for the left and right filed/property values.
The emitted code is slightly more complex, but still about as fast as I now check for IsFinal methods and use Call instead of CallVirt when possible. This optimization is in place for property get calls, and the call the CompareTo, so it is a bit faster.
I also fixed an issue if you compared a whole bunch of attributes and blew the generate IL so large that the loop-break label wasn't reachable by a short branch (nobody reported this, just noticed in code review).
I've updated both the DynamicSorter.zip file and the Utilites.zip file (the latter has other updates to improve fxCop compliance).
The emitted code for "FirstName, lastName, Gender" [String property, double field, Enum property, respectively] now looks like this:
IL_0000: ldarg.0 IL_0001: callvirt System.String get_FirstName()/DynamicComparerSample.Person IL_0006: dup IL_0007: brtrue.s IL_0018 IL_0009: pop IL_000a: ldarg.1 IL_000b: callvirt System.String get_FirstName()/DynamicComparerSample.Person IL_0010: brtrue.s IL_0015 IL_0012: ldc.i4.0 IL_0013: br.s IL_0023 IL_0015: ldc.i4.m1 IL_0016: br.s IL_0023 IL_0018: ldarg.1 IL_0019: callvirt System.String get_FirstName()/DynamicComparerSample.Person IL_001e: call Int32 CompareTo(System.String)/System.String IL_0023: dup IL_0024: brtrue IL_0060 IL_0029: pop IL_002a: ldarg.0 IL_002b: ldfld Double age/DynamicComparerSample.Person IL_0030: stloc.0 IL_0031: ldloca.s V_0 IL_0033: ldarg.1 IL_0034: ldfld Double age/DynamicComparerSample.Person IL_0039: call Int32 CompareTo(Double)/System.Double IL_003e: dup IL_003f: brtrue IL_0060 IL_0044: pop IL_0045: ldarg.0 IL_0046: callvirt DynamicComparerSample.Gender get_Gender()/DynamicComparerSample.Person IL_004b: box DynamicComparerSample.Gender IL_0050: ldarg.1 IL_0051: callvirt DynamicComparerSample.Gender get_Gender()/DynamicComparerSample.Person IL_0056: box DynamicComparerSample.Gender IL_005b: call Int32 CompareTo(System.Object)/System.Enum IL_0060: ret
Posts
4 comments:
Hi Marc,
I received your question from my blog. Emitting an ordinary 'call' for final methods, and 'callvirt' for others, is OK. However, you could actually just use 'callvirt's for all methods, and the CLR's JIT compiler will be intelligent enough to use a static dispatch when it knows it's safe to do so. This is what the C# 2.0 compiler does.
Cheers,
joe
Thanks for the input. I realized that the callvirt was safe in either case, but my benchmarks actually showed a bit better performance for call. Odd. Is checking IsFinal the best way to know it's safe, since I know the type of the variable, it seems safe.
We have a list objects with a property that we are trying to sort by. The propery in question is another list of objects.
The first list made of an object with a property:
Property Offices as List(of MarketingOffice)
...
MarketingOffice
Property Branch as Office
Property IsPrimary as Boolean
...
Office
Property Code as Char
...
We need to be able to sort by offices. The original list has two objects in.
Object 1
Offices=
{MarketingOffice, Primary=True, Branch = Office, Code = H}
{MarketingOffice, Primary=False, Branch = Office, Code = M}
Object 2
Offices=
{MarketingOffice, Primary=True, Branch = Office, Code = M}
We need to able to do a sort by Offices and have the results come out:
H,M
M
When use the dynamic comparer we get the following:
GenericArguments[0], 'Business.Entities.MarketingOffice', on 'System.Nullable`1[T]' violates the constraint of type parameter 'T'.
It is throwing an exception at:
public static bool IsComparable(Type valueType, out bool isNullable)
{
isNullable = valueType.IsGenericType
&& !valueType.IsGenericTypeDefinition
&& valueType.IsAssignableFrom(typeof(Nullable<>).MakeGenericType(valueType.GetGenericArguments()[0]));
return (typeof(IComparable).IsAssignableFrom(valueType)
|| typeof(IComparable<>).MakeGenericType(valueType).IsAssignableFrom(valueType)
|| isNullable);
}
Please help...
If you can send me a simple class that has the properties you are trying to use, I'll happily fix it. You can attach it up on CodePlex.
Post a Comment