Exception for Jmat.Real.lambertw, newton loop step

• could not determine a ground truth

  1. wj = -1.5580172454196658e+97
  2. x = 8.650877258471071e-54

Specification

Math

\[\begin{array}{l} \\ \begin{array}{l} t_0 := wj \cdot e^{wj}\\ wj - \frac{t\_0 - x}{e^{wj} + t\_0} \end{array} \end{array} \]

FPCore

(FPCore (wj x)
 :precision binary64
 (let* ((t_0 (* wj (exp wj)))) (- wj (/ (- t_0 x) (+ (exp wj) t_0)))))

C

double code(double wj, double x) {
	double t_0 = wj * exp(wj);
	return wj - ((t_0 - x) / (exp(wj) + t_0));
}

Fortran

real(8) function code(wj, x)
    real(8), intent (in) :: wj
    real(8), intent (in) :: x
    real(8) :: t_0
    t_0 = wj * exp(wj)
    code = wj - ((t_0 - x) / (exp(wj) + t_0))
end function

Java

public static double code(double wj, double x) {
	double t_0 = wj * Math.exp(wj);
	return wj - ((t_0 - x) / (Math.exp(wj) + t_0));
}

Python

def code(wj, x):
	t_0 = wj * math.exp(wj)
	return wj - ((t_0 - x) / (math.exp(wj) + t_0))

Julia

function code(wj, x)
	t_0 = Float64(wj * exp(wj))
	return Float64(wj - Float64(Float64(t_0 - x) / Float64(exp(wj) + t_0)))
end

MATLAB

function tmp = code(wj, x)
	t_0 = wj * exp(wj);
	tmp = wj - ((t_0 - x) / (exp(wj) + t_0));
end

Wolfram

code[wj_, x_] := Block[{t$95$0 = N[(wj * N[Exp[wj], $MachinePrecision]), $MachinePrecision]}, N[(wj - N[(N[(t$95$0 - x), $MachinePrecision] / N[(N[Exp[wj], $MachinePrecision] + t$95$0), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]]

Reproduce

herbie shell --seed 2024257 
(FPCore (wj x)
  :name "Jmat.Real.lambertw, newton loop step"
  :precision binary64

  :alt
  (! :herbie-platform default (let ((ew (exp wj))) (- wj (- (/ wj (+ wj 1)) (/ x (+ ew (* wj ew)))))))

  (- wj (/ (- (* wj (exp wj)) x) (+ (exp wj) (* wj (exp wj))))))

Please file a bug report with this information.

Backtrace

first: contract violation expected: (and/c list? (not/c empty?)) given: #f		L	C
run-egg	/home/nightlies/herbie/eclass-test-rev/src/core/egg-herbie.rkt	1179	0
simplify-batch	/home/nightlies/herbie/eclass-test-rev/src/core/simplify.rkt	21	0
(unnamed)	/usr/local/racket/collects/racket/contract/private/arrow-higher-order.rkt	379	33
lower-approximations	/home/nightlies/herbie/eclass-test-rev/src/core/patch.rkt	20	0
generate-candidates	/home/nightlies/herbie/eclass-test-rev/src/core/patch.rkt	145	0
run-iter!	/home/nightlies/herbie/eclass-test-rev/src/core/mainloop.rkt	66	0
run-improve!	/home/nightlies/herbie/eclass-test-rev/src/core/mainloop.rkt	43	0
get-alternatives/report	/home/nightlies/herbie/eclass-test-rev/src/api/sandbox.rkt	187	0
(unnamed)	/home/nightlies/herbie/eclass-test-rev/src/api/sandbox.rkt	283	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