\[x = 77617 \land y = 33096\]

\[\left(\left(333.75 \cdot {y}^{6} + \left(x \cdot x\right) \cdot \left(\left(\left(\left(\left(\left(11 \cdot x\right) \cdot x\right) \cdot y\right) \cdot y - {y}^{6}\right) - 121 \cdot {y}^{4}\right) - 2\right)\right) + 5.5 \cdot {y}^{8}\right) + \frac{x}{2 \cdot y}\]

\left(\left(333.75 \cdot {y}^{6} + \left(x \cdot x\right) \cdot \left(\left(\left(\left(\left(\left(11 \cdot x\right) \cdot x\right) \cdot y\right) \cdot y - {y}^{6}\right) - 121 \cdot {y}^{4}\right) - 2\right)\right) + 5.5 \cdot {y}^{8}\right) + \frac{x}{2 \cdot y}

(FPCore (x y)
 :precision binary64
 (+
  (+
   (+
    (* 333.75 (pow y 6.0))
    (*
     (* x x)
     (-
      (- (- (* (* (* (* 11.0 x) x) y) y) (pow y 6.0)) (* 121.0 (pow y 4.0)))
      2.0)))
   (* 5.5 (pow y 8.0)))
  (/ x (* 2.0 y))))

double code(double x, double y) {
	return (((333.75 * pow(y, 6.0)) + ((x * x) * (((((((11.0 * x) * x) * y) * y) - pow(y, 6.0)) - (121.0 * pow(y, 4.0))) - 2.0))) + (5.5 * pow(y, 8.0))) + (x / (2.0 * y));
}

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2021060 
(FPCore (x y)
  :name "Rump's expression from Stadtherr's award speech"
  :precision binary64
  :pre (and (== x 77617.0) (== y 33096.0))
  (+ (+ (+ (* 333.75 (pow y 6.0)) (* (* x x) (- (- (- (* (* (* (* 11.0 x) x) y) y) (pow y 6.0)) (* 121.0 (pow y 4.0))) 2.0))) (* 5.5 (pow y 8.0))) (/ x (* 2.0 y))))

Backtrace

Failed to produce proof for (.f64 (neg.f64 (.f64 (cbrt.f64 (pow.f64 y 6)) (cbrt.f64 (pow.f64 y 6)))) (cbrt.f64 (pow.f64 y 6))) to (neg.f64 (pow.f64 y 6))		L	C
for-loop	/data/pavpan/nightlies/herbie/egg-generate-proof/src/core/simplify.rkt	167	8
(unnamed)	/data/pavpan/nightlies/herbie/egg-generate-proof/src/core/simplify.rkt	149	6
egraph-add-exprs	/data/pavpan/nightlies/herbie/egg-generate-proof/egg-herbie/main.rkt	154	0
with-egraph	/data/pavpan/nightlies/herbie/egg-generate-proof/egg-herbie/main.rkt	74	0
(unnamed)	/data/pavpan/nightlies/herbie/egg-generate-proof/src/core/simplify.rkt	79	0
simplify!	/data/pavpan/nightlies/herbie/egg-generate-proof/src/mainloop.rkt	236	0
run-iter!	/data/pavpan/nightlies/herbie/egg-generate-proof/src/mainloop.rkt	360	0
run-improve	/data/pavpan/nightlies/herbie/egg-generate-proof/src/mainloop.rkt	377	0
(unnamed)	/data/pavpan/nightlies/herbie/egg-generate-proof/src/sandbox.rkt	54	6
run	/opt/racket-7.9/share/pkgs/profile-lib/main.rkt	39	2
profile-thunk	/opt/racket-7.9/share/pkgs/profile-lib/main.rkt	9	0
(unnamed)	/opt/racket-7.9/collects/racket/engine.rkt	42	24