Re: Can you write code directly in CIL ???

Peter,

You don't understand a fundamental concept to .NET and CIL. Yes, there
are compilers that will perform optimization of IL to a certain degree.

However, when the managed code is run, the CLR will take the CIL and
then compile it into native code. At this point in time, it is free to
optimize, or not optimize, or mangle your code in any way you want when
making the transition from CIL to native code.

When you are dealing with assembly language in general, you have
complete control of what is going on, memory allocation, deallocation,
execution, etc, etc. With the CLR, this is taken out of your hands to a
degree.

For example, have you considered, what happens when a Garbage Collection
(GC) occurs while your function is running? If it is in complete managed
code, then there is nothing that you can do about it, and your function will
resume running when the GC is complete. Depending on what is happening on
the machine at the time, combined with what your program is doing, etc, etc,
it is very feasible that your code will take more than 1/10th of a second.

Just because it looks like assembly language, don't assume that CIL is
assembly language. There are some very different things going on under the
hood.

--
- Nicholas Paldino [.NET/C# MVP]
- mvp@xxxxxxxxxxxxxxxxxxxxxxxxxxx

"Peter Olcott" <olcott@xxxxxxx> wrote in message
news:xj2sf.37906$QW2.34052@xxxxxxxxxxxxx
>I want to be able to stick with purely managed code, if possible. I just
>need this 100 line function to run as fast as if it was hand tweaked
>assembly language. I have examined CIL, for the most part it is essentially
>assembly language. From what I understand any optimizations take place
>before the CIL is generated. When I designed this system (in 1998) I had
>hand tweaked assembly language in mind for this crucial function all along.
>
> "Nicholas Paldino [.NET/C# MVP]" <mvp@xxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote
> in message news:%23RjK3$oCGHA.2040@xxxxxxxxxxxxxxxxxxxxxxx
>> Peter,
>>
>> Not at all. When the CLR gets a hold of the JIT, it is free to
>> perform any optimizations it deems necessary, and that might not
>> necessarily be in line with what you are expecting.
>>
>> My recommendation would be to use Managed C++ to create a wrapper to
>> your unmanaged code which uses It Just Works (IJW, seriously). You
>> should get a managed interface, and the best possible performance (for
>> this specific situation, not all situations) between managed an unmanaged
>> code.
>>
>>
>> --
>> - Nicholas Paldino [.NET/C# MVP]
>> - mvp@xxxxxxxxxxxxxxxxxxxxxxxxxxx
>>
>> "Peter Olcott" <olcott@xxxxxxx> wrote in message
>> news:_51sf.37898$QW2.37853@xxxxxxxxxxxxx
>>>I need the best possible execution speed. I have found that there is a
>>>large difference in the quality of the code generated by the various
>>>compilers. I have 16,000 hours of development time in my current project.
>>>There is a 100 line function that must take no longer than 1/10 second to
>>>execute. I can just barely achieve this with MSVC++ 6.0. MSVC++ 7.0 has
>>>had some of its optimizations disabled. I eventually will need to port
>>>this to C# .NET. This is a case where hand tweaked assembly language
>>>would be appropriate. I figured that hand tweaked CIL would be the .NET
>>>equivalent of hand tweaked assembly language.
>>>
>>> "Nicholas Paldino [.NET/C# MVP]" <mvp@xxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote
>>> in message news:OCvd7unCGHA.2644@xxxxxxxxxxxxxxxxxxxxxxx
>>>> Peter,
>>>>
>>>> You can write it, but you would have to create a module with IL, and
>>>> then compile that into your assembly (or just write the whole
>>>> assembly).
>>>>
>>>> Also, what optimizations do you think you can make? Ultimately, you
>>>> suffer from the fact that Windows is not a real-time OS, and nothing
>>>> you can do will change that. On top of that, the JIT is what's going
>>>> to optimize your code again after you try to, so you might actually end
>>>> up hurting yourself more than helping yourself.
>>>>
>>>> If you post the code you are trying to optimize, we can try and tell
>>>> you where you might make some improvements, but dipping down to the IL
>>>> level is most likely not going to help you much.
>>>>
>>>>
>>>> --
>>>> - Nicholas Paldino [.NET/C# MVP]
>>>> - mvp@xxxxxxxxxxxxxxxxxxxxxxxxxxx
>>>>
>>>>
>>>> "Peter Olcott" <olcott@xxxxxxx> wrote in message
>>>> news:7t%rf.37887$QW2.9998@xxxxxxxxxxxxx
>>>>> Cab you write code directly in the Common Intermediate language? I
>>>>> need to optimize a critical real-time function.
>>>>>
>>>>
>>>>
>>>
>>>
>>
>>
>
>


.

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