Specification

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

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

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

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

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

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

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

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

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

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

\begin{array}{l}

\\
\cos^{-1} \left(1 - x\right)
\end{array}

Reproduce

herbie shell --seed 2024035 
(FPCore (x)
  :name "bug323 (missed optimization)"
  :precision binary64
  :pre (and (<= 0.0 x) (<= x 0.5))

  :herbie-target
  (* 2.0 (asin (sqrt (/ x 2.0))))

  (acos (- 1.0 x)))

Please file a bug report with this information.

Backtrace

list-ref: index too large for list index: 256 in: '(#f #t #t #t #t #t #t #t #t #t #t #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 #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 #f #f #f #f #f #f #f #f #f...		L	C
valid-splitindices?	/home/nightlies/herbie/zane-regimes-2/src/core/regimes.rkt	170	0
(unnamed)	.../private/arr-i.rkt	961	8
option-on-expr	/home/nightlies/herbie/zane-regimes-2/src/core/regimes.rkt	106	0
infer-splitpoints	/home/nightlies/herbie/zane-regimes-2/src/core/regimes.rkt	39	0
loop	/home/nightlies/herbie/zane-regimes-2/src/core/regimes.rkt	27	2
loop	/home/nightlies/herbie/zane-regimes-2/src/core/regimes.rkt	27	2
loop	/home/nightlies/herbie/zane-regimes-2/src/core/regimes.rkt	27	2
loop	/home/nightlies/herbie/zane-regimes-2/src/core/regimes.rkt	27	2
extract!	/home/nightlies/herbie/zane-regimes-2/src/mainloop.rkt	365	0
run-improve!	/home/nightlies/herbie/zane-regimes-2/src/mainloop.rkt	339	0
get-alternatives/report	/home/nightlies/herbie/zane-regimes-2/src/sandbox.rkt	169	0
(unnamed)	/home/nightlies/herbie/zane-regimes-2/src/sandbox.rkt	262	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