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IBM Releases Compiler for Power4 and G5
davids-world.com writes "IBM offers its optimized XLC compiler not just for Intel CPUs, but also for its own G5 processor (article in German at Heise). Unlike gcc, it is optimized for the G5 and achieves a major boost in speed, as first results show. I guess we will have to compare the new benchmark data (once available) with the data we get with the optimized Intel compiler for Xeon. The compiler is available for download now."
Lest anyone forget, Apple beat Intel in real world benchmarks... so the PC fanboys cried that SPEC benchmarks are the real measurement to gague speed... (probably because the comparisons were much closer when conducted this way). When SPEC benchmarks were displayed, these same fanboys cried that Intel's compiler wasn't used (instead the same compiler between platforms). Apple replied that its fairer to normalize the compiler between platforms and that while Intel could have achieved higher results when their compiler was used, Apple could do the same. So, here is that compiler. When/if the G5 outperforms Intel's best, what will the fanboys rally cry be next?
And is there a particular reason why IBM couldn't apply their work towards gcc? So much for the whole open-source, contribute-to-the-community philosophy.
Maybe they just didn't feel like it. Maybe they just preferred working with their own code. IBM's contributed, a lot, it doesn't mean that they're now servants of the open source community.
Believe it or not, people DO sometimes run singular tasks on hardware which they want highly optimized...and believe it or not, you can actually install more than one compiler on your system at a time(yes, I know, amazing!)
Please help metamoderate.
IBM has contributed more to the open source community than I would venture to guess any other corporation on earth. (think of the code, projects, money, support, etc). I would not be so quick to blast them for not doing everything under an open source license. Encourage yes, but let's be civil about this. IBM is not just blowing smoke about OSS, they have put their money, time, and products where their mouth is.
Finkployd
Why would they use GCC as a base? It's not intended to compile over a wide range of platforms, just the pSeries processors (which includes the G5), so it's not like they need to be able to port it to x86. When you code a compiler for one fixed architecture you can (and almost always do) end up with HUGE speed increases, since you get to exploit all the fun capabilities of a chip without having to worry about compatibilty.
Put simply, IBM wasn't that interested in improving the cross-platform GCC this time. They were interested in improving a number of their OWN compilers (not just C/C++, Fortran too!) for their OWN architecture.
And is there a particular reason why IBM couldn't apply their work towards gcc?
Yes.
GCC rejected alot of their patches. GCC is a cross paltform compiler, the maintainers can be very picky about adding code that only helps one platform.
IBM has contributed quite a bit to GCC, but GCC is not the proper place for a heavily optimised platform-specific compiler effort.
"The worst tyrannies were the ones where a governance required its own logic on every embedded node." - Vernor Vinge
And is there a particular reason why IBM couldn't apply their work towards gcc? So much for the whole open-source, contribute-to-the-community philosophy.
First off, most companies develop compilers for their hardware/software because they have the behind-the-scenes knowledge necessary to produce a superior product, and therefore, make money off of it. It's called having a competitive advantage, and I see nothing wrong with that.
Second, who says that they won't eventually work to get these performance enhancements included into a future release of GCC? Just because they haven't done so yet does not mean that they never will.
Rule #1 -- Politics always trumps technology.
I know everyone wants to know why they did not just contribute to GCC, but seriously people, I imagine they have their reasons.
Perhaps they wanted something done in a timly manner without waiting for the GCC people to accept their patches. Perhaps they felt a more elegant solution could be achieved by building their own compiler from scratch. Maybe they think GCC is a piece of crap (which for high performance computing, it is).
Just because IBM support open source does not mean they are obligated to do everything for the sole purpose of advancing the movement.
Finkployd
Eh, I wouldn't say that GCC is "worthless", it's just that its worth lies in an area that has nothing to do with high-performance computing. Or even mid-performance computing. :)
GCC's primary virtue is that it exists. For practically every computing platform on the planet, there's a famliar, stable toolchain that produces repeatable results. You can't optimize a program that doesn't exist in the first place, and GCC is the tool that's allowed many if not most of the programs we use on a daily basis to exist. There's value in that.
News for Nerds. Stuff that Matters? Like hell.
No, I don't mean scientific computing. I mean high performance computing. SP clusters, Linux clusters, weather modeling, the stuff that large universities do. No offense but where I am we run significantly larger clusters than SARA has ever seen.
GCC is a great compiler, I use it daily. Better than Intel and IBM for performance (expecially FORTRAN) it is NOT. It was designed as a cross compiler and in that it shines. But it is not all things to all people.
I certainly did not flame GCC and all the people who work on it, come back down off your high horse. All I did was list some reasons why IBM may not have used GCC, one of which is that most of the HPC people I know and work with have tested it and found it to be unacceptable for what they do.
That said, I certainly can see a day when GCC IS the best performing compiler, hands down. I believe open source will eventually overtake most commercial applications due to the momentium it currently has. However it would be silly of me to say that MySQL is better than Oracle, when it clearly is not (yet).
Finkployd
the Intel C compiler spanks every other available x86 compiler
... you point it at some real code, nothing happens. Why is this?
:)
It used to, but it's a close call these days.
SSE/SIMD support is, in the words of one of my assembly-programmer friends, "awe-inspiring."
No it's not, it's fucking awful. Sure, the hype is good, the docs (which are actually very good) show a loop being unrolled to some SIMD instructions, including a little cleanup at the end in scalar instructions. You code it up, it goes
It's not magic, that's why. You put an exit condition in the loop, you break vectorising. If everything isn't lined up on nice 16 (?) byte boundaries, you break vectorising. Once you've gone through making sure all the conditions are met you realise that it's easier just to use the intrinsics in the first place.
Intrinsics, BTW, are very cool and much easier to code than you would have thought. GCC has them too
Dave
I write a blog now, you should be afraid.
Interesting to note that Objective C is much closer to raw C than C++, and as such yes. You can do some stuff with it that's worthwhile.
Also note that David Stes released his POC, which is an Objective-C->C compiler with a runtime he uses (actually it's a bit more than Objective-C) to run ObjC code today.
Apple will probably use this new compiler to recompile their CoreFoundation stuff, which is all C stuff that Carbon and Cocoa tap into. So, a simple recompile of CoreFoundation should net good speed improvements on G4s and MUCH better results on a G5.
So even if IBM chooses not to directly support Objective-C, Apple can still benefit in the short term while they rustle up their very own ObjC->C system (which is NOT a very challenging feat, considering the ObjC runtime is a relatively simple-to-use C library).
Slashdot. It's Not For Common Sense
Can't we talk about Macs on Slashdot without having to talk about whether they're overpriced or slow or whatever? I have a Mac, I like it, I use it for lots of things. I'd like to be able to discuss it, rather than just read x86 users' posts about how much better their platform is & why. This article is about a complier, not comparison shopping. Could we stick to that please??