Bug#1086188: nickle: please make the build reproducible

[Chris Lamb]

Source: nickle
Version: 2.97
Severity: wishlist
User: reproducible-builds at lists.alioth.debian.org
Usertags: randomness
X-Debbugs-Cc: reproducible-bugs at lists.alioth.debian.org

Hi Keith,

Whilst working on the Reproducible Builds effort, we noticed that
nickle could not be built reproducibly.

Looks like an interesting one in usr/share/nickle/test/math-tables.5c

 @@ -1218,15 +1218,15 @@
     { .angle = π *      -1.91999999999999993, .sin =       0.24868988716485535, .cos =       0.96858316112863097 },
     { .angle =          -1.90999999999999992, .sin =      -0.94301993129001060, .cos =      -0.33273624568084514 },
     { .angle = π *      -1.90999999999999992, .sin =       0.27899110603922966, .cos =       0.96029368567694295 },
     { .angle =          -1.89999999999999991, .sin =      -0.94630008768741447, .cos =      -0.32328956686350335 },
 -   { .angle = π *      -1.89999999999999991, .sin =       0.30901699437494767, .cos =       0.95105651629515353 },
 +   { .angle = π *      -1.89999999999999991, .sin =       0.30901699437494762, .cos =       0.95105651629515353 },
     { .angle =          -1.88999999999999990, .sin =      -0.94948561486463046, .cos =      -0.31381055935888225 },

                                     ---------------------------------------> ^
                                                                             this
                                                                            column

... plus similar changes in the same file. Here is the code in
question:

    #define FMT	"%25.17f"

    double
    print_val(double x)
    {
      if (isnan(x))
        return 10000;
      if (x > 1e10)
        return 9999;
      if (x < -1e10)
        return 9999;
      if (fabs(x) < 1e-20)
        return 0;
      return x;
    }

    […]

    for (a = -800; a <= 800; a += 1) {
        double a_f = a / 100;
        printf ("\t{ .angle =     " FMT ", .sin = " FMT ", .cos = " FMT " },\n",
            a_f, print_val(sin(a_f)), print_val(cos(a_f)));
        printf ("\t{ .angle = π * " FMT ", .sin = " FMT ", .cos = " FMT " },\n",
            a_f, print_val(sin(M_PI * a_f)), print_val(cos(M_PI * a_f)));
    }

It's easier to see in HTML format:

    https://tests.reproducible-builds.org/debian/rb-pkg/unstable/amd64/nickle.html

This is a native build on amd64/x86_64 both runs, and yet I can't
reproduce it locally. I thought the point of IEEE 754 or whatever it
was was to ensure this sort of thing didn't happen across runs? :)

Hope you can help.


Regards,

-- 
      ,''`.
     : :'  :     Chris Lamb
     `. `'`      lamby at debian.org / chris-lamb.co.uk
       `-