Re: optimized code

All depends on what exactly you are measuring , how you are comparing and
what you are expecting.
But suppose we are talking about code generated by MSFT VS2005 C#, C++ and
C++/CLI, first, you should understand that you are basically using the same
math library (the CRT library) for all three. That means that the results
should be comparable for both C# and C++/CLI, and that C++ should take
advantage of the back-end optimizer which can do a better job than the JIT
compiler.
Anyway what I have measured so far using VS2005, is a slight advantage (<
5%) for C++/CLI over C# and a larger advantage (<20%) for C++ oner C#.

The difference between C# and C++/CLI is due to a better optimized IL
produced by the C++ compiler, when enabling max. optimizations (enables the
fastest FP unit mode).
The difference between managed and unmanaged C++ is due to the extra
redirection (through the CLR) between managed code(well, JIT'd ) and the
math library.
Note that your mileage may vary, therefore, I would suggest you do your
homework, run some benchmarks, compare and make a language decision. Note
however, that performance should never be the only criterion to select a
development language (or platform). Remember faster is not always better,
especially when talking about FP arithmetics.


Willy.


"Fred Mellender" <nospamPlease_fredm@xxxxxxxxxxxxxxx> wrote in message
news:YTxlf.702$EE4.354@xxxxxxxxxxxxxxxx
> Can anyone comment on C# vs. C++ for floating point performance with V2?
>
> In
> http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dndotnet/html/dotnetperftips.asp
> we
> read:
>
> "Floating Point?The v1 JIT does not currently perform all the FP-specific
> optimizations that the VC++ backend does, making floating point operations
> more expensive for now. "
>
> Has this been improved? Can anyone quantify the difference in
> performance. I have a highly computation-intensive program written in C#
> and wonder what the difference would be if I were to rewrite in C++.
>
> "Willy Denoyette [MVP]" <willy.denoyette@xxxxxxxxxx> wrote in message
> news:uhWpH9r%23FHA.2472@xxxxxxxxxxxxxxxxxxxxxxx
>>
>> "Daniel O'Connell [C# MVP]" <onyxkirx@xxxxxxxxxxxxxxxxxxxxx> wrote in
>> message news:eNZ5Ljq%23FHA.1676@xxxxxxxxxxxxxxxxxxxxxxx
>>>
>>> "Mike" <vimakefile@xxxxxxxxx> wrote in message
>>> news:Oj7acNp%23FHA.2424@xxxxxxxxxxxxxxxxxxxxxxx
>>>> Is it still true that the managed C++ compiler will produce much better
>>>> opimizations than the C# compiler, or have some of the more
>>>> global/aggressive opimizations been rolled into the 2005 compiler?
>>>>
>>>
>>> Yes, the Managed C++ compiler should still be better. the C# compiler
>>> still doesn't go very far as far as optimizations go, AFAIK anyway. They
>>> are left to the JIT.
>>>
>>>
>> The same applies to the "managed C++" compiler, common sub-expressions
>> and loop invariants are handled by the JIT not by the compiler fron-ends.
>> The managed C++ compiler generates IL, sometimes it does a better job,
>> but I've seen IL code that was better optimized by the C# compiler.
>> Anyway the differences are < 5% (both sides), MS said that they will
>> focus on the JIT to further optimize, not in the C++ front-end.
>>
>>
>> Willy.
>>
>>
>
>


.

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