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GCC 4.9 vs. 5.3 vs. 6.0 Compiler Benchmarks On Debian 8.4

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  • GCC 4.9 vs. 5.3 vs. 6.0 Compiler Benchmarks On Debian 8.4

    Phoronix: GCC 4.9 vs. 5.3 vs. 6.0 Compiler Benchmarks On Debian 8.4

    With GCC 6.1 due out soon with its plethora of new features and improvements, I decided to run some fresh benchmarks this week of GCC 4.9.3 vs. GCC 5.3 vs. GCC 6.0.0 on a Debian stable system...

    Phoronix, Linux Hardware Reviews, Linux hardware benchmarks, Linux server benchmarks, Linux benchmarking, Desktop Linux, Linux performance, Open Source graphics, Linux How To, Ubuntu benchmarks, Ubuntu hardware, Phoronix Test Suite

  • #2
    Cool!

    BTW, what are the noise margins here?

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    • #3
      Don't see big difference between them. Then what do newer gcc versions do? Supporting more kinds of cpu's? Generating faster code?

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      • #4
        Originally posted by dxxvi View Post
        Don't see big difference between them. Then what do newer gcc versions do? Supporting more kinds of cpu's? Generating faster code?

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        • #5
          Originally posted by vladpetric View Post
          Cool!

          BTW, what are the noise margins here?
          It's shown on each of the graphs when relevant.
          Michael Larabel
          https://www.michaellarabel.com/

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          • #6
            1. Such simple tests are pointless. Main improvements lie in -flto part and C++14 features etc, if we ignore new architectures here ( Zen etc). So main test example would be to try it on some big library and/or executable, compiled with aggressive optimisations ( -O3 at least) and -flto. Simple tests as those shown, are adequate just for quick check for regressions, nothing more.

            2. gcc-6.0 is AFAIK in the works, so shouldn't this be the first gcc-6 release ?



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            • #7
              Originally posted by Brane215 View Post

              2. gcc-6.0 is AFAIK in the works, so shouldn't this be the first gcc-6 release ?
              gcc version numbering is the oddest I have ever seen

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              • #8
                Originally posted by Brane215 View Post
                1. Such simple tests are pointless. Main improvements lie in -flto part and C++14 features etc, if we ignore new architectures here ( Zen etc). So main test example would be to try it on some big library and/or executable, compiled with aggressive optimisations ( -O3 at least) and -flto. Simple tests as those shown, are adequate just for quick check for regressions, nothing more.

                2. gcc-6.0 is AFAIK in the works, so shouldn't this be the first gcc-6 release ?
                I think -O3 is a bit harsh since it is generally advised NOT to use O3 since it can actually result in incorrect calculations, etc. -O2 is a more reasonable choice, don't you think?

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                • #9
                  No O3 will not produce incorrect results. Unsafe optimizations are only done for Ofast. O3 will just take longer time and produce larger binaries than O2.

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                  • #10
                    -O3 -march=native is usually the default for Phoronix tests, isn't it? I mean, no point in comparing the speed of unoptimized code.

                    The only reason people recommend not to use -O3 is that it often breaks incorrect code, i.e. code that relies on undefined behaviour to behave in a specific way, which it may do with -O2. Can't blame the compiler for that.

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