Exception for 2-ancestry mixing, negative discriminant

Specification

Math

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

FPCore

(FPCore (g h)
 :precision binary64
 (* 2.0 (cos (+ (/ (* 2.0 PI) 3.0) (/ (acos (/ (- g) h)) 3.0)))))

C

double code(double g, double h) {
	return 2.0 * cos((((2.0 * ((double) M_PI)) / 3.0) + (acos((-g / h)) / 3.0)));
}

Java

public static double code(double g, double h) {
	return 2.0 * Math.cos((((2.0 * Math.PI) / 3.0) + (Math.acos((-g / h)) / 3.0)));
}

Python

def code(g, h):
	return 2.0 * math.cos((((2.0 * math.pi) / 3.0) + (math.acos((-g / h)) / 3.0)))

Julia

function code(g, h)
	return Float64(2.0 * cos(Float64(Float64(Float64(2.0 * pi) / 3.0) + Float64(acos(Float64(Float64(-g) / h)) / 3.0))))
end

MATLAB

function tmp = code(g, h)
	tmp = 2.0 * cos((((2.0 * pi) / 3.0) + (acos((-g / h)) / 3.0)));
end

Wolfram

code[g_, h_] := N[(2.0 * N[Cos[N[(N[(N[(2.0 * Pi), $MachinePrecision] / 3.0), $MachinePrecision] + N[(N[ArcCos[N[((-g) / h), $MachinePrecision]], $MachinePrecision] / 3.0), $MachinePrecision]), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]

Reproduce

herbie shell --seed 2024196 
(FPCore (g h)
  :name "2-ancestry mixing, negative discriminant"
  :precision binary64
  (* 2.0 (cos (+ (/ (* 2.0 PI) 3.0) (/ (acos (/ (- g) h)) 3.0)))))

Please file a bug report with this information.

Backtrace

vector-set!: contract violation expected: exact-nonnegative-integer? given: -2 argument position: 2nd first argument...: '#(#f #t #t #t #t #t #t #t #t #t #t #t #t #f #t #t #t #t #f #f #f #f #f #f #t #f #f #f #f #f #f #t #t #f #f #f #f #f #f #f #f #f #f #f #f #f #f #f #f #f #f #f #f #f #f #f #f #f #f #f #f #f #f #f)		L	C
backward-pass	/home/nightlies/rival/main/eval/adjust.rkt	8	0
rival-machine-adjust	/home/nightlies/rival/main/eval/run.rkt	98	0
rival-machine-full	/home/nightlies/rival/main/eval/main.rkt	16	0
rival-apply	/home/nightlies/rival/main/eval/main.rkt	56	0
(unnamed)	/usr/local/racket/collects/racket/contract/private/arrow-val-first.rkt	486	18
(unnamed)	/home/nightlies/herbie/main/src/sampling.rkt	159	4
ival-eval	/home/nightlies/herbie/main/src/sampling.rkt	153	0
<eval-prog-real>	/home/nightlies/herbie/main/src/sampling.rkt	188	2
compute-local-errors	/home/nightlies/herbie/main/src/core/localize.rkt	105	0
batch-localize-errors	/home/nightlies/herbie/main/src/core/localize.rkt	91	0
localize!	/home/nightlies/herbie/main/src/mainloop.rkt	187	0
run-iter!	/home/nightlies/herbie/main/src/mainloop.rkt	70	0
mutate!	/home/nightlies/herbie/main/src/mainloop.rkt	62	0
run-improve!	/home/nightlies/herbie/main/src/mainloop.rkt	48	0
get-alternatives/report	/home/nightlies/herbie/main/src/sandbox.rkt	167	0
(unnamed)	/home/nightlies/herbie/main/src/sandbox.rkt	261	6
(unnamed)	/usr/local/racket/share/pkgs/profile-lib/main.rkt	40	10
profile-thunk	/usr/local/racket/share/pkgs/profile-lib/main.rkt	9	0
(unnamed)	/usr/local/racket/collects/racket/engine.rkt	42	24