Exception for 2-ancestry mixing, negative discriminant

Math

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

C

double f(double g, double h) {
        double r111557 = 2.0;
        double r111558 = atan2(1.0, 0.0);
        double r111559 = r111557 * r111558;
        double r111560 = 3.0;
        double r111561 = r111559 / r111560;
        double r111562 = g;
        double r111563 = -r111562;
        double r111564 = h;
        double r111565 = r111563 / r111564;
        double r111566 = acos(r111565);
        double r111567 = r111566 / r111560;
        double r111568 = r111561 + r111567;
        double r111569 = cos(r111568);
        double r111570 = r111557 * r111569;
        return r111570;
}

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2019194 
(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/master/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
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/master/src/core/localize.rkt	61	0
localize!	/data/pavpan/nightlies/herbie/master/src/mainloop.rkt	123	0
run-iter!	/data/pavpan/nightlies/herbie/master/src/mainloop.rkt	323	0
for-loop	/data/pavpan/nightlies/herbie/master/src/mainloop.rkt	359	4
run-improve47	/data/pavpan/nightlies/herbie/master/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