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Intel C/C++ Compiler Beats GCC
jfonseca writes: "An article from Open Magazine claims the new Intel C/C++ compiler's geometric mean performance on multiple kernels compiled through it reached 47% improvement over GCC. They also predict the end to the ubiquitous GNU compiler due to low performance. Many other compiler/platform combinations also compared. A bit pretentious, yet an interesting read."
I guess I'm not that surprised that the corporation that designed the CPU would produce a more optimized compiler.
The interesting thing is that the Intel compiler's code ran at 'virtually identical' speeds on an Athlon.
I was always under the impression that a vendor supplied compiler would almost always out-perform a generic cross-compiler, which is available on much more other platforms. GCC is all fine and dandy, but it's it shines in other aspects than pure optimization and fast code (they may be faster on some architectures than the vendor supplied compiler, but that's not my point). The produced code x86 was always sub-optimal. Because of that, projects like pgcc exist(ed).
-- The plural of 'anecdote' is not 'data'.
Could this be more full of itself? Somehow I have trouble accepting sweeping generalizations about the fate of compiler technology from someone who obviously dropped out of a creative writing program at some third-rate school.
sic transit gloria mundi
Sometime I analize assembler code produced by gcc-2.95.3 and I am dissapointed. Gcc can do so stupid things like inserting instruction inside - instead outside of loop. Probably gcc3 is fixed, but I heard it still produces slow code (not faster than gcc-2.95.3). So which compiler should I use today?
I know gcc3 is better, becouse it supports more platforms, but what about speed improvements? To have fast inner loop in linux application I must code that loop in assembler. That is a problem for someone, who's creating a computer game.
...at a conference I went to on computer vision. You see, intel also has an optimized computer vision library. They began their talk for the day with the statement "Intel is in the business of selling chips. However, everyone already has enough processor power to do word processing and that sort of thing. We need people to make more complicated applications so that it make these faster chis we come out with worthwhile."
I imagine that similar logic applies to their compiler: they give it away for free (binary version, so they can control it), but build in the hooks that make it work faster with their newer chips than with the competitions' while at the same time encouraging people to write more CPU intensive programs because they have the power to do so.
Ultimately, they succeed at their real goal: to sell more chips. By the way, AFAIK, Intel still gives away its compiler in binary form, though only for Windows. Of course, the last time I checked was a year and a half ago...
Mod me down and I will become more powerful than you can possibly imagine!
It's not exactly new news that Intel's compilers are better than Microsoft's or GCC, as any astute watcher or compiler of SPECbench results can tell you. GCC has never been a performance barn-burner. People who wanted that paid the money, signed the forms, and tweaked their software to run under Intel's compilers.
No, what's great news is that Intel's compilers are available now on Linux. So an ISV like Red Hat can compile the OS (or specific math libraries) on them for either real-user or benchmarking benefits.
"Driving a stake through the heart" of GCC is a gross exaggeration, given the ubiquity, freedom, and free beer nature of GCC. "Giving GCC a kick in the pants" might be more accurate. And a good thing, too.
--LP
Compaq's (formerly DEC) C compiler for alpha's have always been excellent and far ahead of GCC. The problem is that a lot of compilers (we haven't tested the intel yet) won't compile all the code that you may want or need. In the *NIX env. GCC seems to provide the highest level of compatibility over a wide variety of platforms n(SUN, AXI, BSD, Linux, Tru-64, Windows, et al).
Until there is only one chip left to support (Intel is fast working on it, with the support of turncoats Compaq, HP and others) GCC will be a viable option. GCC is a great "cross platform" compiler that works for much of the current written open soruce code base. You can get that compiler to work for many different OSs and archs.
In the end, remember apache wasn't the fastest web server, but it was the "most correct" and it was free! It really doesn't matter how well your C compiler works if it won't compile your code or run on your system.
"Science is about ego as much as it is about discovery and truth " - I said it, so sue me.
It seems to me that GNU and the FSF has become a bunch of bureaucrats and politicians who forgot what free software is all about.
Today, the real dynamic and successful projects are mostly non-GNU: KDE, Apache, Linux, Wine, etc.
Today, GNOME is the only GNU-project that can be called a bit dynamic, and I think this is because of a lot of 3rd party involvement via the GNOME-foundation and the fact that RMS is not the final authority in the GNOME-project.
What breakthroughs has there been in RMS-led projects in the last - say - 5 years? I can't think of any.
Of course, gcc is still the best open-source compiler we have, and no alternative is in sight (unless Intel open-sources theirs which is highly unlikely), but I see it as a weak spot in the free software-world. How long have we been waiting for a decsent c++ compiler? Maybe I'm paranoid, but maybe RMS is not very enthusiastic about C++ support because GNOME would look even worse in comparison to KDE, once a good C++ compiler is available?
I think we need a lot more non-GNU involvment for gcc (gcc-foundation?) to get some fresh blood into this project. And if RMS doesn't allow that, we need a fork.
But of course, that's just my opinion, so flame me.
It seems like it would be a nice move for AMD to support GCC optimizations for Athlon processors. The idea would be similar to IBM supporting Linux as a way of chipping away at market dominance by Microsoft.
AMD should supply GPL'd contributions to GCC that optimize code for its Athlon processors. This would give them a relatively cheap way of putting out a competing compiler to Intel's proprietary version since it would leverage all the work that has already been done by the GCC group. It could also make them the preferred chip for open source OS's by ensuring that Athlons run GCC code faster than any other processor. This would be strategically very valuable at a time that they are about to push their new 64 bit instructions while Linux is simultaneously becoming viable/validated as an enterprise platform. Since GCC is not limited to Linux, these performance enhancements would also translate into gains for non-open source development projects as well.
All in all, it seems that this could be a be a great way for AMD to give developers a way to produce AMD optimized code while at the same time encouraging the use of their new 64 bit instructions in the booming open source OS server/workstation market.
Now, as for GNU C and benchmarks, GNU C has never produced the fastest code on any platform. Unless you lived under a rock and never did any high performance computing, you'd know that. And if you took the time to look at the GNU C documentation, you'd also know that this is no accident. But to most GNU C users, this fact never mattered. GNU C generates decent code and it has many other attributes that make it the "best" compiler for many applications.
You see, there is another misunderstanding that you and Bill Gates share: you think that there is a single "best" solution to everything. In real life, there isn't. What is "best" for you isn't necessarily "best" for me, and there may well be no way to reconcile our conflicting needs in the same piece of software.
I do agree that Slashdot moderation tends to exclude voices like yours and I think that's wrong. Why? So that one can point out how uninformed and confused you actually are.
Is that a good thing? Internet Explorer dominates the web browser market for much the same reasons, whether or not there are better alternatives available. Now we have a proliferation of web sites that only work with IE instead of standard HTML, and all the other well-documented problems.
It would be an advantage for the Linux world if it was easier to port code from other platforms. Most of that code isn't written with GCC, it's written with VC++, C++ Builder, CodeWarrior, etc. If you're going to do this, standards compliance and ease of portability are very important.
I don't know how good GCC is these days; it used to have quite a good reputation for standard compliance and quality of generated code, but that was a couple of years back. If it hasn't kept up -- I said "if", because I don't think this article demonstrates that either way -- and the Linux community religiously stick with it based on philosophical arguments rather than technical merit, surely they'll just be shooting themselves in the foot?
If you disagree, post your argument. (-1, Overrated) isn't your personal censorship tool for views you don't like.
So I downloaded the Linux_cpu.zip
/lib/libm.so.6 (0x4002b000)
/lib/libc.so.6 (0x4004d000)
/lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
/lib/libm.so.6 (0x4002b000)
/lib/libc.so.6 (0x4004d000)
/lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
It contains a shared and a static library, and two binaries. Full of symbols, so I stip them
61124 bytes in libcxa.a
49356 bytes in libcxa.so.1
90380 bytes oblcpu_gcc
131736 bytes oblcpu_icc
$ ldd oblcpu_*
oblcpu_gcc:
libm.so.6 =>
libc.so.6 =>
oblcpu_icc:
libm.so.6 =>
libcxa.so.1 => not found
libc.so.6 =>
Ok, so the icc version needs the shared library to be loaded as well.
$ size libcxa.so.1 oblcpu_*
text data bss dec hex filename
22839 3008 124 25971 6573 libcxa.so.1
70563 15860 1923912 2010335 1eacdf oblcpu_gcc
93858 24236 1923768 2041862 1f2806 oblcpu_icc
Codesize for gcc: 70563 bytes
Codesize for icc: 93858 + 22839 = 116697
Hmm, that is a 65% increase in code size! Not to mention the increase in data size (can anybody say 'lookup table' or 'buffering'?)
Hmm... I wonder if they tried gcc optimizations such as '-funroll-all-loops'. Too bad they didn't provide the source so we could verify the results.
I got a free evaluation CD from Intel with the February issue of "Linux Magazine", so I'll be doing my own comparisons thank you.
--- Hindsight is 20/20, but walking backwards is not the answer.
The gain is obviously highly dependant on the application.
I tested the Intel compiler against GCC using Robert Hyatt's excellent crafty chess engine and the speedup was only 7%. (Athlon 1.2Ghz)
On a PIII-500Mhz the speedup was only 2.5%
Of course for other application results with vary, but I for me the Intel compiler isn't worth the money or the effort.
Hats off to the GCC team for building one of the greatest tools of all time. You can't beat GCC for sheer usefulness and ubiquity.
The hobbyist licence is free.
But it prohibits selling copies of the compiler's output. Thus, if you make a CD of your software, you probably can't even sell it for $5 to cover duplication costs. Plus, such a restrictions is incompatible with the "no restrictions on selling" language in the GNU GPL.
Although aren't most Linux distros only compiled for the i386 anyway, ignoring what i686 optimizations exist in GCC?
AFAIK, the Linux distributions are compiled with something like -march=i486 -mcpu=i686 which means roughly "Use only those instructions available in i486 and up, but schedule for i686." (Source: GCC 2.95.3 docs, info gcc invoking submodel i386)
Will I retire or break 10K?
He actually makes an interesting point. I mean, they released a g++ 3.0 that would not correctly compile KDE. It appears that the associated ABI bugs are not going to be addressed until 3.1. And they've dropped the ball on it badly enough that it's been forked twice over the last few years. Up to and including 2.95.x, there were a lot of very obvious and annoying bugs with g++ (no namespace std, no stringstream class, no ios_base class, etc) I don't see any conspiracy theories, but it doesn't seem that gcc have historically given C++ a very high priority.