Linked by ebasconp on Fri 10th Jun 2011 22:22 UTC
Benchmarks "Google has released a research paper that suggests C++ is the best-performing programming language in the market. The internet giant implemented a compact algorithm in four languages - C++, Java, Scala and its own programming language Go - and then benchmarked results to find 'factors of difference'."
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RE[5]: GCC isn't all that great
by Valhalla on Mon 13th Jun 2011 06:02 UTC in reply to "RE[4]: GCC isn't all that great"
Valhalla
Member since:
2006-01-24


Stupid code? Sure it was a trivial example, but that was deliberate.

Having two comparisons within the loop was obviously poor coding in this example, which you expected the compiler to fix for you.


Do we really want to go down the route of saying programmers need to check up on GCC's assembly output?

If you find that the performance is not what you'd expect out of the given code, you will profile and look at assembly output of the performance hotspots, doesn't matter if it's GCC, VC, ICC, Clang/LLVM.


Should students be taught to avoid legal C constructs which give the GCC optimizer a hard time?

Legal constructs does not equal efficient code. Compilers have never been able to turn shitty code into good code. If you know of one, please inform me, I'd buy it in a second.


I wish someone could test this for us, Intel boasts very aggressive SSE optimization.

I compiled your snippet with Clang 2.9, it didn't vectorize it either until I exchanged the len vars with constants just like in the case with GCC. Again I doubt ICC would do it either.

Again, this function within the context of a whole program would likely yield a different result (definately if PGO was used). For instance it would be interesting disecting the output of some of the micro-benchmarks over at language-shootout.

On a slightly off-topic note, anyone have any experience with the ekopath4 compiler suite? it appears that it is to be released as open source (gplv3) and judging by the performance benchmarks it appears to offer some gpgpu solution:

http://www.phoronix.com/scan.php?page=article&item=phoronix_dirndl_...

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