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Re: Double-precision floating point arithmetics behaves differently in G

From: Panicz Maciej Godek
Subject: Re: Double-precision floating point arithmetics behaves differently in Guile and in C
Date: Sun, 26 Sep 2021 13:55:20 +0200

I forgot to mention that I run Guile in an Emacs session running in a WSL
console on Windows 10.
The tests of the C code that I've been performing so far were executed in
an MSYS terminal, but I have just tried running them in WSL console, and
the radii get ridiculous values.

While the values used to generate the points are the following:

center '[-65.12 -50.54 88.66]:
radii: '[83.95 47.13 45.56]
rotation: '[[9.633871e-001   1.363818e-001   -2.308359e-001]
                [-1.734094e-001  9.735887e-001   -1.485064e-001]
                [2.044857e-001   1.830983e-001   9.615927e-001]]

and the values reconstructed in Guile are:

  #:center (65.10194623013226 -88.58460232582514 -50.721825868168324)
  #:radii (83.94677717528019 45.56525864722978 47.12037877216948)
  #:rotation ((-0.9633227088329351 0.2307406879308479 0.13699669185777974)
                   (0.173638969876562 0.14674930301995573
                   (-0.20459439578586436 -0.961885324244193

(the signs and the order of radii differ, but it seems that the rotation
matrix compensates for that)

in the case of MSYS (MinGW 64-bit) I get the following values: = [90.13, -68.76, -42.46]
approx_e.radius = [178.83, 97.08, 100.43]
approx_e.rotation(3x3) =
        -9.634121049254586e-001 1.734020884333972e-001
        -2.314281253565038e-001 -1.535574849495593e-001
        -1.351966674037161e-001 -9.728061546592428e-001

but in the case of the WSL console, I get = [90.13, -68.76, -42.46]
approx_e.radius = [1347844355973136335704668472606720.00,
731678657375689861259088782950400.00, 756961648396782369967223865344000.00]
approx_e.rotation(3x3) =
        -9.634121049254428e-01  1.734020884334219e-01
        -2.314281253566119e-01  -1.535574849499134e-01
        -1.351966674036449e-01  -9.728061546591822e-01

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