.NET versus C++ compiled code

[Joe]

Hi,

I am looking to start a brand new project. Yeahhh! ;-)


The code will do a lot of processor intensive processing. I mean a
lot
of loops to archieve big calculations. You know recursive functions
and everything. Since I am a .NET programmer I have a question. Is
there a real big difference in term of performance (based on the
processors we have in our machine nowadays) between a .NET (C#)
program and the same one written in C++ compiled with Microsoft or
Borland C++ compiler.


I know that is a big question! Probably that too much factors can
influence the overall result.


Thanks.

 

[Peter Duniho]

[...]
Is
there a real big difference in term of performance (based on the
processors we have in our machine nowadays) between a .NET (C#)
program and the same one written in C++ compiled with Microsoft or
Borland C++ compiler.

I know that is a big question! Probably that too much factors can
influence the overall result.

My experience has been that the overhead is much smaller than I would
have expected before I started doing .NET programming a few years ago.
Under normal conditions, where the code is not entirely CPU-bound, the
overhead is practically invisible, because the code is mostly waiting
for other things anyway.

If you have code that _is_ completely CPU-bound, you may be able to
measure a difference. If that code takes a long time to run, that
difference may translate to a genuinely noticeable delay. But it's
impossible to say in advance what sort of exact difference you might
notice without knowing the specifics of your algorithm.

Also in my experience, it has been true that if something needs speeding
up, usually the first place to start is fixing the algorithm, which is
almost never written optimally to start with. You might speed something
up by 10-25% (depending on a variety of factors) moving code to C++,
whereas fixing the algorithm can often speed things up by 50%, 100%, or
more. Algorithm problems are much more common than platform problems.

There are always exceptions, of course, but those will only be
identified by first making sure you have the most optimal algorithm, and
then doing an actual comparison between the C# and C++ versions of the
algorithm. It's impossible to say in advance what difference, if any,
there might be.

Pete

 

[=?iso-8859-1?q?Horacio_Nu=F1ez_Hern=E1ndez?=]

Hi,

I am looking to start a brand new project. Yeahhh! ;-)

The code will do a lot of processor intensive processing. I mean a
lot
of loops to archieve big calculations. You know recursive functions
and everything. Since I am a .NET programmer I have a question. Is
there a real big difference in term of performance (based on the
processors we have in our machine nowadays) between a .NET (C#)
program and the same one written in C++ compiled with Microsoft or
Borland C++ compiler.

I know that is a big question! Probably that too much factors can
influence the overall result.

Thanks.

The CLR spent some time compiling the IL to native, but this is only
the first a function is called but the .NET allocation of objects is
more efficient that the traditional C++. As you say there are ver
factors. Anyway you can compile the application for an especial
plataform, an generate a native code instead an IL.
Another issue can be create some functions in c++ and interop later.
Or you can try the C++/CLI language and have both managed an umnanaged
shipping the best of two worlds

The desicion is yours!

regards

 

[Ben Voigt [C++ MVP]]

The CLR spent some time compiling the IL to native, but this is only
the first a function is called but the .NET allocation of objects is
more efficient that the traditional C++. As you say there are ver
factors. Anyway you can compile the application for an especial
plataform, an generate a native code instead an IL.
Another issue can be create some functions in c++ and interop later.
Or you can try the C++/CLI language and have both managed an umnanaged
shipping the best of two worlds

Please note that the Microsoft C++ compiler (used also for C++/CLI) does a
lot of optimizations not supported by C#.

However, for code heavy on recursive functions, you should definitely
consider a functional language, where the optimizers are written
specifically to deal with recursion.

 

[=?ISO-8859-1?Q?Arne_Vajh=F8j?=]

The code will do a lot of processor intensive processing. I mean a
lot
of loops to archieve big calculations. You know recursive functions
and everything. Since I am a .NET programmer I have a question. Is
there a real big difference in term of performance (based on the
processors we have in our machine nowadays) between a .NET (C#)
program and the same one written in C++ compiled with Microsoft or
Borland C++ compiler.

Even for CPU intensive code I would expect the .NET code to
be almost as fast as the native code - within 20% of the
C++ compiler (with maximum optimization - C# will be faster
than default C++ compiler options). But for a few cases it
is possible to code C++ in a way that are much faster than C#
sometimes 2-3 times as fast. Whether you code contain
examples of that is impossible to say upfront.

Arne

 

[Micky Duncan]

Hi,
I once ported my c++ ray tracer to c# and found that the c# code was
approximately 10% slower than c++. Ray tracing is probably once of the most
recursive algorithms and is quite heavy on floating point and math - lots of
sqrt() and such.

Though performance is generally paramount in Ray tracing, the productivity
gain in writing in c# over c++ I am willing to lose that small performance
loss.

Besides, I can always fine tune some aspects and write in c++ interop.