Performance difference between C++ and C# for mathematics

Question

I would like to preface this with I'm not trying to start a fight. I was wondering if anyone had any good resources that compared C++ and C# for mathematically intensive code? My gut impression is that C# should be significantly slower, but I really have no evidence for this feeling. I was wondering if anyone here has ever run across a study or tested this themselves? I plan on running some tests myself, but would like to know if anyone has done this in a rigorous manner (google shows very little). Thanks.

EDIT: For intensive, I mean a lot of sin/cos/exp happening in tight loops

Answer 1

C# will be slower in general, but not significantly so. In some cases, depending on the structure of the code, C# can actually be faster, as JIT analysis can frequently improve the performance of a long-running algorithm.

Edit: Here's a nice discussion of C# vs C++ performance

Edit 2:

"In general" is not really accurate. As you say, the JIT compiler can actually turn your MSIL into faster native code that the C++ compiler because it can optimize for the hardware it is running on.

You must admit, however, that the act of JIT compiling itself is resource intensive, and there are runtime checks that occur in managed code. Pre-compiled and pre-optimized code will always be faster than just JITted code. Every benchmark comparison shows it. But long-running processes that can have a fair amount of runtime analysis can be improved over pre-compiled, pre-optimized native code.

So what I said was 100% accurate. For the general case, managed code is slightly slower than pre-compiled, pre-optimized code. It's not always a significant performance hit, however, and for some cases JIT analysis can improve performance over pre-optimized native code.

Answer 2

For straight mathematical functions asking if C# is faster than C++ is not the best question. What you should be asking

Is the assembly produced by the CLR JITer more or less efficient than assembly generated by the C++ compiler

The C# compiler has much less influence on the speed of purely mathmatical operations than the CLR JIT does. It would have almost identical performance as other .Net languages (such as VB.Net if you turn off overflow checing).

Answer 3

There are extensive benchmarks here:

http://shootout.alioth.debian.org/u32q/benchmark.php?test=all&lang=csharp&lang2=gpp&box=1

Note this compares the Mono JIT to C++. AFIAK there are no extensive benchmarks of Microsoft's implementation out there, so almost everything you will hear is hearsay. :(

Answer 4

I would consider using Mono.Simd to accelerate some operations. The minus is that on MS runtime it's not accelerated.

Answer 5

I think you're asking the wrong question. You should be asking if C++ on can beat out the .NET family of languages in mathematical computation. Have a gander at F# timing comparisons for Runge Kutta

Answer 6

You do not define "mathematically intensive" very well (understatement for: not at all).

An attempt to a breakdown:

• For the basic Sin/Cos/Log functions I would not expect much difference.

• For linear algebra (matrices) I would expect .NET to loose out, the (always enforced) bounds checking on arrays is only optimized away under some circumstances.

You will probably have to benchmark something close to your intended domain.

Answer 7

For basic math library functions there won't be much difference because C# will call out to the same compiled code that C++ would use. For more interesting math that you won't find in the math library there are several factors that make C# worse. The Current JIT doesn't support SSE instructions that you would have access to in C++.