Intel C++ compiler as an alternative to Microsoft's?

Question

Is anyone here using the Intel C++ compiler instead of Microsoft's Visual c++ compiler?

I would be very interested to hear your experience about integration, performance and build times.

Answer 1

I've had only one experience with this compiler, compiling STLPort. It took MSVC around 5 minutes to compile it and ICC was compiling for more than an hour. It seems that their template compilation is very slow. Other than this I've heard only good things about it.

Here's something interesting:

Intel's compiler can produce different versions of pieces of code, with each version being optimised for a specific processor and/or instruction set (SSE2, SSE3, etc.). The system detects which CPU it's running on and chooses the optimal code path accordingly; the CPU dispatcher, as it's called.

"However, the Intel CPU dispatcher does not only check which instruction set is supported by the CPU, it also checks the vendor ID string," Fog details, "If the vendor string says 'GenuineIntel' then it uses the optimal code path. If the CPU is not from Intel then, in most cases, it will run the slowest possible version of the code, even if the CPU is fully compatible with a better version."

OSnews article here

Answer 2

The last time the company I work for compared the two was about a year ago, (maybe 2). The Intel compiler generated faster code, usually only a bit faster, but in some cases quite a bit.

But it couldn't handle some of the MS language extensions that we depended on, so we ended up sticking with MS. It was VS 2005 that we were comparing it to. And I'm wracking my brain to remember exactly what MS extension the Intel compiler couldn't handle. I'll come back and edit this post if I can remember.

Answer 3

I tried using Intel C++ at my previous job. IIRC, it did indeed generate more efficient code at the expense of compilation time. We didn't put it to production use though, for reasons I can't remember.

One important difference compared to MSVC is that the Intel compiler supports C99.

Answer 4

I'm not using Intel C++ compiler at work / personal (I wish I would).

I would use it because it has:

• Excellent inline assembler support. Intel C++ supports both Intel and AT&T (GCC) assembler syntaxes, for x86 and x64 platforms. Visual C++ can handle only Intel assembly syntax and only for x86.

• Support for SSE3, SSSE3, and SSE4 instruction sets. Visual C++ has support for SSE and SSE2.

• Is based on EDG C++, which has a complete ISO/IEC 14882:2003 standard implementation. That means you can use / learn every C++ feature.

Answer 5

Anecdotally, I've found that the Intel compiler crashes more frequently than Visual C++. Its diagnostics are a bit more thorough and clearly written than VC's. Thus, it's possible that the compiler will give diagnostics that weren't given with VC, or will crash where VC didn't, making your conversion more expensive.

However, I do believe that Intel's compiler allows you to link with Microsoft runtimes like the CRT, easing the transition cost.

If you are interoperating with managed code you should probably stick with Microsoft's compiler.

Recent Intel compilers achieve significantly better performance on floating-point heavy benchmarks, and are similar to Visual C++ on integer heavy benchmarks. However, it varies dramatically based on the program and whether or not you are using link-time code generation or profile-guided optimization. If performance is critical for you, you'll need to benchmark your application before making a choice. I'd only say that if you are doing scientific computing, it's probably worth the time to investigate.

Intel allows you a month-long free trial of its compiler, so you can try these things out for yourself.

Answer 6

The Intel compiler is the most advanced C++ compiler available, it has a number of advantages over for instance the Microsoft Visual C++ compiler, and one major drawback. The advantages include:

• Very good SIMD support, as far as I've been able to find out, it is the compiler that has the best support for SIMD instructions.

• Supports both automatic parallelization (multi core optimzations), as well as manual (through OpenMP), and does both very well.

• Support CPU dispatching, this is really important, since it allows the compiler to target the processor for optimized instructions when the program runs. As far as I can tell this is the only C++ compiler available that does this, unless G++ has introduced this in their yet.

• It is often shipped with optimized libraries, such as math and image libraries.

However it has one major drawback, the dispatcher as mentioned above, only works on Intel CPU's, this means that advanced optimizations will be left out on AMD cpu's. There is a workaround for this, but it is still a major problem with the compiler.

To work around the dispatcher problem, it is possible to replace the dispatcher code produced with a version working on AMD processors, one can for instance use Agner Fog's asmlib library which replaces the compiler generated dispatcher function. Much more information about the dispatching problem, and more detailed technical explanations of some of the topics can be found in the Optimizing software in C++ paper - also from Anger (which is really worth reading).

On a personal note I have used the Intel c++ Compiler with Visual Studio 2005 where it worked flawlessly, I didn't experience any problems with microsoft specific language extensions, it seemed to understand those I used, but perhaps the ones mentioned by John Knoeller were different from the ones I had in my projects.

While I like the Intel compiler, I'm currently working with the microsoft C++ compiler, simply because of the financial extra investment the Intel compiler requires. I would only use the Intel compiler as an alternative to Microsofts or the GNU compiler, if performance were critical to my project and I had a the financial part in order ;)

Answer 7

Intel C++ Compiler has AMAZING (human) support. Talking to Microsoft can literally take days. My non-trivial issue was solved through chat in under 10 minutes (including membership verification time).