\[2 \cdot \cos \left(\frac{2 \cdot \pi}{3} + \frac{\cos^{-1} \left(\frac{-g}{h}\right)}{3}\right)\]

2 \cdot \cos \left(\frac{2 \cdot \pi}{3} + \frac{\cos^{-1} \left(\frac{-g}{h}\right)}{3}\right)

double f(double g, double h) {
        double r130181 = 2.0;
        double r130182 = atan2(1.0, 0.0);
        double r130183 = r130181 * r130182;
        double r130184 = 3.0;
        double r130185 = r130183 / r130184;
        double r130186 = g;
        double r130187 = -r130186;
        double r130188 = h;
        double r130189 = r130187 / r130188;
        double r130190 = acos(r130189);
        double r130191 = r130190 / r130184;
        double r130192 = r130185 + r130191;
        double r130193 = cos(r130192);
        double r130194 = r130181 * r130193;
        return r130194;
}

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2019194 +o rules:numerics
(FPCore (g h)
  :name "2-ancestry mixing, negative discriminant"
  (* 2.0 (cos (+ (/ (* 2.0 PI) 3.0) (/ (acos (/ (- g) h)) 3.0)))))

Backtrace

get-representation: Unknown representation #f		L	C
(unnamed)	/data/pavpan/nightlies/herbie/js-tweaks/src/core/localize.rkt	23	13
hash-ref!	/opt/racket-7.0/collects/racket/private/more-scheme.rkt	376	2
map	/opt/racket-7.0/collects/racket/private/map.rkt	35	13
parse-loop30	/opt/racket-7.0/collects/racket/match/compiler.rkt	418	15
hash-ref!	/opt/racket-7.0/collects/racket/private/more-scheme.rkt	376	2
map	/opt/racket-7.0/collects/racket/private/map.rkt	35	13
parse-loop30	/opt/racket-7.0/collects/racket/match/compiler.rkt	418	15
hash-ref!	/opt/racket-7.0/collects/racket/private/more-scheme.rkt	376	2
map	/opt/racket-7.0/collects/racket/private/map.rkt	35	13
parse-loop30	/opt/racket-7.0/collects/racket/match/compiler.rkt	418	15
hash-ref!	/opt/racket-7.0/collects/racket/private/more-scheme.rkt	376	2
localize-error	/data/pavpan/nightlies/herbie/js-tweaks/src/core/localize.rkt	61	0
localize!	/data/pavpan/nightlies/herbie/js-tweaks/src/mainloop.rkt	123	0
run-iter!	/data/pavpan/nightlies/herbie/js-tweaks/src/mainloop.rkt	323	0
for-loop	/data/pavpan/nightlies/herbie/js-tweaks/src/mainloop.rkt	359	4
run-improve47	/data/pavpan/nightlies/herbie/js-tweaks/src/mainloop.rkt	342	0
(unnamed)	/opt/racket-7.0/collects/racket/private/more-scheme.rkt	261	28
run	/opt/racket-7.0/share/pkgs/profile-lib/main.rkt	39	2
profile-thunk16	/opt/racket-7.0/share/pkgs/profile-lib/main.rkt	9	0
(unnamed)	/opt/racket-7.0/collects/racket/private/more-scheme.rkt	261	28