performance

Phoronix conclusions distort their results, shown with the example of GCC vs. LLVM/Clang On AMD's FX-8350 Vishera

Phoronix recently did a benchmark of GCC vs. LLVM on AMD hardware. Sadly their conclusion did not fit the data they showed. Actually it misrepresented the data so strongly, that I decided to speak up here instead of having my comments disappear in their forums. This post was started on 2013-05-14 and got updates when things changed - first for the better, then for the worse.

Update 3 (the last straw, 2013-11-09): In the recent most blatant attack by Phoronix on copyleft programs - this time openly targeted at GNU - Michael Larabel directly misrepresented a post from Josh Klint to badmouth GDB (Josh confirmed this1). Josh gave a report of his initial experience with GDB in a Kickstarter Update in which he reported some shortcomings he saw in GDB (of which the major gripe is easily resolved with better documentation2) and concluded with “the limitations of GDB are annoying, but I can deal with it. It's very nice to be able to run and debug our editor on Linux”. Michael Larabel only quoted the conclusion up to “annoying” and abused that to support the claim that game developers (in general) call GDB “crap” and for further badmouthing of GDB. With this he provided the straw which I needed to stop reading Phoronix: Michael Larabel is hostile to copyleft and in particular to GNU and he goes as far as rigging test results3 and misrepresenting words of others to further his agenda. I even donated to Phoronix a few times in the past. I guess I won’t do that again, either. I should have learned from the error of the german pirates and should have avoided reading media which is controlled by people who want to destroy what I fight for (sustainable free software).
Update 2 (2013-07-06): But the next went down the drain again… “Of course, LLVM/Clang 3.3 still lacks OpenMP support, so those tests are obviously in favor of GCC.” — I couldn’t find a better way to say that those tests are completely useless while at the same time devaluing OpenMP support as “ignore this result along with all others where GCC wins”…
Update (2013-06-21): The recent report of GCC 4.8 vs. LLVM 3.3 looks much better. Not perfect, but much better.


  1. Josh Klint from Leadwerks confirmed that Phoronix misrepresented his post and wrote a followup-post: » @ArneBab That really wasn't meant to be controversial. I was hoping to provide constructive feedback from the view of an Xcode / VS user.« » Slightly surprised my complaints about GDB are a hot topic. I can make just as many criticisms of other compilers and IDEs.« » The first 24 hours are the best for usability feedback. I figure if they notice a pattern some of those things will be improved.« » GDB Follwup «@Leadwerks, 2:04 AM - 11 Nov 13, 2:10 AM - 11 Nov 13 and @JoshKlint, 2:07 AM - 11 Nov 13, 8:48 PM - 11 Nov 13

  2. The first-impression criticism from Josh Klint was addressed by a Phoronix reader by pointing to the frame command. I do not blame Josh for not knowing all tricks: He wrote a fair account of his initial experience with GDB (and he said later that he wrote the post after less than 24 hours of using GDB, because he considers that the best time to provide feedback) and his experience can serve as constructive criticism to improve tutorials, documentation and the UI of GDB. Sadly his visibility and the possible impact of his work on free software made it possible for Phoronix to abuse a personal report as support for a general badmouthing of the tool. In contrast the full message of Josh Klint ended really positive: Although some annoyances and limitations have been discovered, overall I have found Linux to be a completely viable platform for application development. — Josh Klint, Leadwerks 

  3. I know that rigging of tests is a strong claim. The actions of Michael Larabel deserve being called rigging for three main reasons: (1) Including compile-time data along with runtime performance without clear distinction between both, even though compile-time of the full code is mostly irrelevant when you use a proper build system and compile time and runtime are completely different classes of results, (2) including pointless tests between incomparable setups whose only use is to relativate any weakness of his favorite system and (3) blatantly lying in the summaries (as I show in this article). 

Reducing the Python startup time

The python startup time always nagged me (17-30ms) and I just searched again for a way to reduce it, when I found this:

The Python-Launcher caches GTK imports and forks new processes to reduce the startup time of python GUI programs.

Python-launcher does not solve my problem directly, but it points into an interesting direction: If you create a small daemon which you can contact via the shell to fork a new instance, you might be able to get rid of your startup time.

To get an example of the possibilities, downl

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((λ()'Dr.ArneBab))



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