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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:

(ellipsoid
#: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
0.9738142277679884)
(-0.20459439578586436 -0.961885324244193
0.18143251146545056)))

(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:

approx_e.center = [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
-2.043742444879810e-001
-2.314281253565038e-001 -1.535574849495593e-001
9.606566096217422e-001
-1.351966674037161e-001 -9.728061546592428e-001
-1.880692600613582e-001

but in the case of the WSL console, I get

approx_e.center = [90.13, -68.76, -42.46]
731678657375689861259088782950400.00, 756961648396782369967223865344000.00]
approx_e.rotation(3x3) =
-9.634121049254428e-01  1.734020884334219e-01
-2.043742444880351e-01
-2.314281253566119e-01  -1.535574849499134e-01
9.606566096216593e-01
-1.351966674036449e-01  -9.728061546591822e-01
-1.880692600617213e-01

```

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