Exception for Logistic function from Lakshay Garg

Specification

Math

\[\begin{array}{l} \\ \frac{2}{1 + e^{-2 \cdot x}} - 1 \end{array} \]

FPCore

(FPCore (x y) :precision binary64 (- (/ 2.0 (+ 1.0 (exp (* -2.0 x)))) 1.0))

C

double code(double x, double y) {
	return (2.0 / (1.0 + exp((-2.0 * x)))) - 1.0;
}

Fortran

real(8) function code(x, y)
    real(8), intent (in) :: x
    real(8), intent (in) :: y
    code = (2.0d0 / (1.0d0 + exp(((-2.0d0) * x)))) - 1.0d0
end function

Java

public static double code(double x, double y) {
	return (2.0 / (1.0 + Math.exp((-2.0 * x)))) - 1.0;
}

Python

def code(x, y):
	return (2.0 / (1.0 + math.exp((-2.0 * x)))) - 1.0

Julia

function code(x, y)
	return Float64(Float64(2.0 / Float64(1.0 + exp(Float64(-2.0 * x)))) - 1.0)
end

MATLAB

function tmp = code(x, y)
	tmp = (2.0 / (1.0 + exp((-2.0 * x)))) - 1.0;
end

Wolfram

code[x_, y_] := N[(N[(2.0 / N[(1.0 + N[Exp[N[(-2.0 * x), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]), $MachinePrecision] - 1.0), $MachinePrecision]

Reproduce

herbie shell --seed 2024196 
(FPCore (x y)
  :name "Logistic function from Lakshay Garg"
  :precision binary64
  (- (/ 2.0 (+ 1.0 (exp (* -2.0 x)))) 1.0))

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 #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/zane-odyssey-timeline/src/sampling.rkt	159	4
ival-eval	/home/nightlies/herbie/zane-odyssey-timeline/src/sampling.rkt	153	0
<eval-prog-real>	/home/nightlies/herbie/zane-odyssey-timeline/src/sampling.rkt	188	2
predict-errors	/home/nightlies/herbie/zane-odyssey-timeline/src/explain.rkt	86	0
explain	/home/nightlies/herbie/zane-odyssey-timeline/src/explain.rkt	736	0
explain!	/home/nightlies/herbie/zane-odyssey-timeline/src/mainloop.rkt	339	0
mutate!	/home/nightlies/herbie/zane-odyssey-timeline/src/mainloop.rkt	62	0
run-improve!	/home/nightlies/herbie/zane-odyssey-timeline/src/mainloop.rkt	48	0
get-alternatives/report	/home/nightlies/herbie/zane-odyssey-timeline/src/sandbox.rkt	167	0
(unnamed)	/home/nightlies/herbie/zane-odyssey-timeline/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