Itanium Software Development using C++

Itanium Software Development using C++

Can someone shed some light on the pros and cons of software development for the Itanium using

(a) gcc and Intel C++ compiler under Red Hat Linux 7.2, and
(b) Microsoft .Net 2003 C++ (Version 7) and Intel compiler under Windows XP 64-bit

when the underlying code uses a large number of floating point operations and virtual memory.

Are there any benchmarks available comparing the two scenarios? My experience with Intel C++ compiler and Red Hat Linux 7.2 has been disappointing (on an Itanium 900 MHz workstation). The code performs much slower than when it is compiled and executed on an Intel P4-2.4 GHz machine!

Subby

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Performance comparisons between g++ and ecc are among the reasons for moving toward libstdc++-v3 compatibility. I can't tell from your remarks whether you are considering STL-dependent code. Aside from STL problems, the performance of the Intel compiler on floating point should be considerably better than g++. You may need to work with specific performance tuning, such as comparing -O2 and -O3, inserting #pragma ivdep, and checking the opt_report to see which optimizations are performed. Several of the optimizations associated with effective use of cache occur only at -O3 (software prefetch, load pair scheduling). g++ does none of those, but, since it schedules for Itanium1, there is more time allowed to resolve bank stalls and L2 miss.

My experience with Microsoft C++ is out of date. When I last had the occasion to compare it with ecl, the strengths of the Microsoft compiler were in more complete in-line expansion of standard library functions, not in the operations usually associated with floating point.

In view of the above, you will see that I agree it is often simpler to get good performance on P4. If your criteria include performance on operations which can't be pipelined effectively, there is no way that Itanium can be competitive. On the other side, we have large applications where the performance of 900Mhz Itanium and 3Ghz P4 are close.

You can look at processor performance comparisons on a number of application types at http://www.intel.com/products/benchmarks/server/

I don't have a specific benchmark to send you to, but you may find some help from the SPEC2000 benchmark results at http://www.spec.org/osg/cpu2000/results/ or from the additional benchmarks provided on http://www.ideasinternational.com/benchmark/bench.html

Amanda

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