I've ran into it in practice a few years back, while making WRF (math intensive atmospheric modeling software, I'm maintaining non-commercial soaring prediction site for the bay area) to work on my AMD cluster. Had to patch the executable compiled with the Intel compiler in order to make it work unhindered on AMD's. The patch was just zapping 'Genuine Intel' detection code in the compiled executable... That 'post-linker' patch is available here: http://www.swallowtail.org/naughty-intel.shtml
I was in a parallel programming class where the fastest correct assignments got significant extra credit boosts. Compiling with the intel compiler with optimizations turned on (vs gcc) was often enough to make the difference in getting that extra credit by a significant margin.
Sure, but if merely switching compilers produced a faster binary, then I would expect all programs to be compiled with the better-optimizing compiler. After all, it doesn't take any particular expertise to adjust the value of CC.
There's more to optimization than setting -O3. Learning how various compilers behave and how their optimization features interact with your code are valuable skills and may well have been within the scope of the course. Certainly worthy of extra credit.
The class clearly has a performance component, and so students were expected to learn about optimization. Are they going to learn optimization better or worse if you mandate a single compiler? If merely switching compilers is the best path to performance, is that not a valuable lesson? If switching compilers and doing a bunch of extra work to make the code fast with the new compiler is the best path to performance, have they not learned a great deal?
Some compilers aren't generally available. Hypothetically, what if ICC wasn't available freely to educational users, but some of the students had side-jobs where they used it?
You can always mandate a large set of compilers, make them all available, and leave it up to the students to determine which is fastest. I think that acheives both the competitive/educational goal and the level playing field goal.
I would definitely ban using any compiler that wasn't generally available to the class, or at least disqualify their output from winning the contest. I'd take a generic approach where it's worded just like that, rather than trying to come up with an official set of acceptable compilers, though.
I was trying to build WRF from source a few years ago for a project in grad school, and the bulk of the program was one giant file that crashed gfortran when you tried to compile it. So compiling with a non-Intel compiler can present some problems.
Er, I was building it from source... Don't remember exactly was blocking me from using GCC, vaguely remember something about OpenMP support... The config in question was MPI+OpenMP, where OpenMP was used to parallelize withing a node of a cluster and MPI for the cluster itself.
