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  1. adiwan adiwan

    I need to know why the floating point (double) precision of my Atom N270 is almost perfect around values of 0. I tested 7 different systems and the others are worse. If I restructure my test such that no optimization is possible (separating the computation in different volatile variables) then it is as bad as the others. !coderponies

    Wednesday, 05-Jun-13 15:33:04 UTC from Choqok
    1. adiwan adiwan

      @broniebrown This is the code I used http://pastebin.com/GKChMveB I visualize the sign of the doubles in a 256x256 image (blue negative, red positive, yellow zero).

      Wednesday, 05-Jun-13 15:38:42 UTC from Choqok
    2. Light Light

      @broniebrown i actually ran into this issue a couple times, it has to do with the way your processor manages the variable, double being 8bits. the variable is stored in a algorithm state which gets interpreted. some programming languages manage this better then others but my language of that time period was C++ :/

      Thursday, 13-Jun-13 14:33:17 UTC from web
      1. adiwan adiwan

        @ryanjjjj I found out what this reason is. On 32 bit systems the GCC uses the 387 instructions (for floating point calculations) that actually increase the double/float size for intermediate double/float calculations. On 64 bit systems it is disabled by default because SSE2 is faster and the mixture with 387 is experimental. Depending on how you wrote the code the compiler optimizes in such a way that you have the best accuracy. I made a test so that the compiler doesn't optimize this part and I got a result like in the other cases.

        Thursday, 13-Jun-13 15:15:10 UTC from Choqok
        1. Light Light

          @broniebrown but will it blend? this is the question.

          Thursday, 13-Jun-13 15:22:56 UTC from web
          1. adiwan adiwan

            @ryanjjjj As far as I have read it is not recommended.

            Thursday, 13-Jun-13 16:05:53 UTC from Choqok
            1. Light Light

              @broniebrown not "Recommended" means do it but we are not responsible! *puts laptop processor into blender.*

              Friday, 14-Jun-13 01:14:27 UTC from web
    3. Light Light

      @vt3c OH OH i know that animal... is it applejack!?

      Friday, 14-Jun-13 01:13:37 UTC from web
    4. Light Light

      @vt3c Mayor mare?

      Friday, 14-Jun-13 01:14:58 UTC from web
    5. Light Light

      @vt3c HEY my mother is a very nice lady :c

      Friday, 14-Jun-13 01:18:41 UTC from web
    6. Light Light

      @vt3c 你的爸爸

      Friday, 14-Jun-13 01:19:54 UTC from web
    7. Light Light

      @vt3c :I

      Friday, 14-Jun-13 01:20:48 UTC from web
    8. Light Light

      @vt3c 我做比萨饼和你的香肠！

      Friday, 14-Jun-13 01:23:41 UTC from web
    9. Light Light

      @vt3c 里。Rainbowdash

      Friday, 14-Jun-13 01:35:32 UTC from web