Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>It is most likely because the first invocation of the code was not jitted. I decided to look at the IL and they are virtually identical.</p> <pre><code>Func&lt;int, Foo&gt; func = x =&gt; new Foo(x * 2); Expression&lt;Func&lt;int, Foo&gt;&gt; exp = x =&gt; new Foo(x * 2); var func2 = exp.Compile(); Array.ForEach(func.Method.GetMethodBody().GetILAsByteArray(), b =&gt; Console.WriteLine(b)); var mtype = func2.Method.GetType(); var fiOwner = mtype.GetField("m_owner", BindingFlags.Instance | BindingFlags.NonPublic); var dynMethod = fiOwner.GetValue(func2.Method) as DynamicMethod; var ilgen = dynMethod.GetILGenerator(); byte[] il = ilgen.GetType().GetMethod("BakeByteArray", BindingFlags.NonPublic | BindingFlags.Instance).Invoke(ilgen, null) as byte[]; Console.WriteLine("Expression version"); Array.ForEach(il, b =&gt; Console.WriteLine(b)); </code></pre> <p>This code gets us the byte arrays and prints them to the console. Here is the output on my machine::</p> <pre><code>2 24 90 115 13 0 0 6 42 Expression version 3 24 90 115 2 0 0 6 42 </code></pre> <p>And here is reflector's version of the first function::</p> <pre><code> L_0000: ldarg.0 L_0001: ldc.i4.2 L_0002: mul L_0003: newobj instance void ConsoleApplication7.Foo::.ctor(int32) L_0008: ret </code></pre> <p>There are only 2 bytes different in the entire method! They are the first opcode, which is for the first method, ldarg0 (load the first argument), but on the second method ldarg1 (load the second argument). The difference here is because an expression generated object actually has a target of a <code>Closure</code> object. This can also factor in. </p> <p>The next opcode for both is ldc.i4.2 (24) which means load 2 onto the stack, the next is the opcode for <code>mul</code> (90), the next opcode is the <code>newobj</code> opcode (115). The next 4 bytes are the metadata token for the <code>.ctor</code> object. They are different as the two methods are actually hosted in different assemblies. The anonymous method is in an anonymous assembly. Unfortunately, I haven't quite gotten to the point of figuring out how to resolve these tokens. The final opcode is 42 which is <code>ret</code>. Every CLI function must end with <code>ret</code> even functions that don't return anything.</p> <p>There are few possibilities, the closure object is somehow causing things to be slower, which might be true (but unlikely), the jitter didn't jit the method and since you were firing in rapid spinning succession it didn't have to time to jit that path, invoking a slower path. The C# compiler in vs may also be emitting different calling conventions, and <code>MethodAttributes</code> which may act as hints to the jitter to perform different optimizations.</p> <p>Ultimately, I would not even remotely worry about this difference. If you really are invoking your function 3 billion times in the course of your application, and the difference being incurred is 5 whole seconds, you're probably going to be ok.</p>
    singulars
    1. This table or related slice is empty.
    1. POWhy is Func<> created from Expression<Func<>> slower than Func<> declared directly?
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USnawfal
    1. USMichael B
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. COAre you suggesting that it takes several seconds to JIT compile a function that contains 5 instructions?
      singulars
      1. PO
      1. USGabe
    2. COIm with you on the matter that I shouldnt really care about the small difference. But when you are writting a piece of software which will be judged on its performance, where tests cases like this will be used to meassure it against other competitors it does matter when you rely heavily on delegates and you suddenly see performance decrease by 30-40% compared to the direct approach. Luckily getting the Expression gives me a possibility to optimize what is going on in the lambda and make it even faster than the direct approach.
      singulars
      1. PO
      1. USMartinF
    3. COA bigger thing to sell to higher ups, is that the Expression approach allows you to implement patterns and delegates easier than say doing it by hand. So while we can all agree that hand-tuned C# might be better, if you need specific code for each type or worse instance writing the myriad cases by hand will be a huge developing effort, where as you can write fairly well optimized expression tree that can dynamically generate code to tweak your behavior at runtime.
      singulars
      1. PO
      1. USMichael B
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload