Exception for bug323 (missed optimization)

Specification

\[0 \leq x \land x \leq 0.5\]

Math

\[\begin{array}{l} \\ \cos^{-1} \left(1 - x\right) \end{array} \]

FPCore

(FPCore (x) :precision binary64 (acos (- 1.0 x)))

C

double code(double x) {
	return acos((1.0 - x));
}

Fortran

real(8) function code(x)
    real(8), intent (in) :: x
    code = acos((1.0d0 - x))
end function

Java

public static double code(double x) {
	return Math.acos((1.0 - x));
}

Python

def code(x):
	return math.acos((1.0 - x))

Julia

function code(x)
	return acos(Float64(1.0 - x))
end

MATLAB

function tmp = code(x)
	tmp = acos((1.0 - x));
end

Wolfram

code[x_] := N[ArcCos[N[(1.0 - x), $MachinePrecision]], $MachinePrecision]

Reproduce

herbie shell --seed 2024196 
(FPCore (x)
  :name "bug323 (missed optimization)"
  :precision binary64
  :pre (and (<= 0.0 x) (<= x 0.5))

  :alt
  (! :herbie-platform default (* 2 (asin (sqrt (/ x 2)))))

  (acos (- 1.0 x)))

Please file a bug report with this information.

Backtrace

vector-set!: contract violation expected: exact-nonnegative-integer? given: -1 argument position: 2nd first argument...: '#(#f #t #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
predict-errors	/home/nightlies/herbie/main/src/explain.rkt	86	0
explain	/home/nightlies/herbie/main/src/explain.rkt	736	0
explain!	/home/nightlies/herbie/main/src/mainloop.rkt	339	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