The document discusses the performance of dynamic languages, focusing on C# and metaprogramming concepts including the Dynamic Language Runtime architecture and the use of the 'dynamic' keyword. It explains how metaobjects are utilized for late binding and outlines the functionality of the CallSite class and dynamic metaobjects. Additionally, it highlights practical applications such as fluent XML parsing and the performance implications of Python to C# integration.

1. Dynamic Language Performanceor How I Learned to Love MetaprogrammingW. Kevin Hazzard, C# MVPNoVA Code CampOctober 2009

2. AgendaMetaObjects and MetaProgrammingDynamic Language Runtime ArchitectureThe dynamic keyword in C# 4The CallSite<T> ClassThe CSharpRuntimeBinderDynamicMetaObjectsAdaptive Inline CachingDemonstrationsFluent XML ParsingPerformance of Python to C# Integration

3. Metaobject VisualizationMetaobjectcontrolcreateinvokeBacking ObjectsUsers and programs interact with metaobjects, not directly with their backing objects.

4. DLR Architecture

5. The dynamic Keyword[Dynamic] objectDX = someFunction();dynamic DX = someFunction();DX( ‘A’ );DX.Foo( 1 );DX.Bar = ‘X’;int V = DX.Baz;DX[0] = 100;string S = DX[0];// invoke the object// invoke the Foo member// set the Bar member// convert the Baz member to integer// set index 0 to 100// convert index 0 to stringIs dynamic a new type? NoThe dynamic type is totally static This type is a signal to the compiler to perform late binding

6. Let's Stop and Reflectclass Program{ dynamic Jabberwocky( dynamicarg ) {return arg.foo(); }}[return: Dynamic] object Jabberwocky( [Dynamic] objectarg ) {if (<Jabberwocky>o__SiteContainer2.<>p__Site3 == null) { <Jabberwocky>o__SiteContainer2.<>p__Site3 = CallSite<Func<CallSite, object, object>>.Create(newCSharpInvokeMemberBinder( CSharpCallFlags.None, "foo", typeof( Program ), null, newCSharpArgumentInfo[] { newCSharpArgumentInfo(CSharpArgumentInfoFlags.None, null ) } ) ); }return <Jabberwocky>o__SiteContainer2.<>p__Site3.Target( <Jabberwocky>o__SiteContainer2.<>p__Site3, arg );}

7. The CallSite<T> ClassIn the System.Runtime.CompilerServices namespaceCreated and managed in a static container class for each venueKey members:Create – creates and assign a binderTarget – a delegate that invokes the binderBinder – connects an appropriate metaobject to the underlying call implementation

8. The CSharpRuntimeBinderWhat might these describe?Semantic CheckerSymbol TableExpression Tree CreatorExpression FactoryContext InfoControllerDispatcher

9. What is a metaobject?An object that:May contain info on the:CreatesControlsInvokesDescribesImplementsInterfaces ofType ofMethods ofFields ofProperties ofAttributes of… another object

10. The DynamicMetaObject ClassBinds up “The Twelve" DLR methods

11. All expression tree-orientedBindCreateInstanceBindBinaryOperationBindUnaryOperationBindConvertBindDeleteMemberBindDeleteIndexBindInvokeBindInvokeMemberBindGetMemberBindSetMemberBindGetIndexBindSetIndex

12. IDynamicMetaObjectProviderpublic interface IDynamicMetaObjectProvider{ DynamicMetaObject GetMetaObject( Expression parameter );}Pattern for implementing a custom metaobjectThe returned DynamicMetaObject must implement all twelve binding methods (and more)Lots of Expression Tree knowledge is requiredNot a trivial exercise

13. DynamicObject to the rescue!public class DynamicObject : IDynamicMetaObjectProvider { protected DynamicObject();public virtual DynamicMetaObjectGetMetaObject(...);public virtual boolTryBinaryOperation(...);public virtual boolTryConvert(...);public virtual boolTryCreateInstance(...);public virtual boolTryDeleteIndex(...);public virtual boolTryDeleteMember(...);public virtual boolTryGetIndex(...);public virtual boolTryGetMember(...);public virtual boolTryInvoke(...);public virtual boolTryInvokeMember(...);public virtual boolTrySetIndex(...);public virtual boolTrySetMember(...);public virtual boolTryUnaryOperation(...);}

14. Example – Fluent XML ParsingWouldn't it be nice if we could read and write XML like a set of nested objects without deep knowledge of the XML DOM or LINQ to XML?<books pubdate="2009-06-15"> <book price="45.99" title="Surgery for Dummies"> <id isbn10="4389880339"/> <authors> <author> <name> <first>Mortimer</first> <last>Snerdly</last> </name> <email address="mort@surgery.com"/> </author> </authors> </book></books>WriteLine( books.book[0].authors.author[0].name.first);

15. Fluent XML pARSING in C#Demonstration

16. Adaptive Inline CachingEach CallSite uses 3 levels of cachingLevel 0 – a dynamically generated delegate for some of the call patterns encountered at the siteLevel 1 – a read-only set of rules for all of the call patterns that the site has seen so farLevel 2 – a read-only set of rules that spans multiple call sites

17. What about level 2 cache misses?A level 2 cache miss causes:The creation of a new ruleThe insertion of the new rule into the level 2 cache (on the ActionBinder)The insertion of the new rule into the level 1 cache (on the CallSite rule set)Possible insertion into the level 0 cache (on the CallSite dynamic delegate)

18. Performance ofPython to C# IntegrationDemonstration