\[\begin{array}{l} \mathbf{if}\;b \ge 0.0:\\ \;\;\;\;\frac{2 \cdot c}{\left(-b\right) - \sqrt{b \cdot b - \left(4 \cdot a\right) \cdot c}}\\ \mathbf{else}:\\ \;\;\;\;\frac{\left(-b\right) + \sqrt{b \cdot b - \left(4 \cdot a\right) \cdot c}}{2 \cdot a}\\ \end{array}\]

\begin{array}{l}
\mathbf{if}\;b \ge 0.0:\\
\;\;\;\;\frac{2 \cdot c}{\left(-b\right) - \sqrt{b \cdot b - \left(4 \cdot a\right) \cdot c}}\\

\mathbf{else}:\\
\;\;\;\;\frac{\left(-b\right) + \sqrt{b \cdot b - \left(4 \cdot a\right) \cdot c}}{2 \cdot a}\\

\end{array}

double f(double a, double b, double c) {
        double r32424 = b;
        double r32425 = 0.0;
        bool r32426 = r32424 >= r32425;
        double r32427 = 2.0;
        double r32428 = c;
        double r32429 = r32427 * r32428;
        double r32430 = -r32424;
        double r32431 = r32424 * r32424;
        double r32432 = 4.0;
        double r32433 = a;
        double r32434 = r32432 * r32433;
        double r32435 = r32434 * r32428;
        double r32436 = r32431 - r32435;
        double r32437 = sqrt(r32436);
        double r32438 = r32430 - r32437;
        double r32439 = r32429 / r32438;
        double r32440 = r32430 + r32437;
        double r32441 = r32427 * r32433;
        double r32442 = r32440 / r32441;
        double r32443 = r32426 ? r32439 : r32442;
        return r32443;
}

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2019323 
(FPCore (a b c)
  :name "jeff quadratic root 2"
  :precision binary64
  (if (>= b 0.0) (/ (* 2 c) (- (- b) (sqrt (- (* b b) (* (* 4 a) c))))) (/ (+ (- b) (sqrt (- (* b b) (* (* 4 a) c)))) (* 2 a))))

Backtrace

dict-ref: no value for key: 'branch32423 in: '((a . binary64) (b . binary64) (c . binary64))		L	C
for-loop	/data/pavpan/nightlies/herbie/fix-interface-bugs/src/points.rkt	106	4
make-sampler	/data/pavpan/nightlies/herbie/fix-interface-bugs/src/points.rkt	99	0
prepare-points-intervals	/data/pavpan/nightlies/herbie/fix-interface-bugs/src/points.rkt	121	0
for-loop	/data/pavpan/nightlies/herbie/fix-interface-bugs/src/core/regimes.rkt	233	9
sindices->spoints	/data/pavpan/nightlies/herbie/fix-interface-bugs/src/core/regimes.rkt	194	0
f33	/opt/racket-7.2/collects/racket/match/compiler.rkt	507	40
get-final-combination	/data/pavpan/nightlies/herbie/fix-interface-bugs/src/mainloop.rkt	369	0
(unnamed)	/opt/racket-7.2/collects/racket/private/more-scheme.rkt	261	28
run	/opt/racket-7.2/share/pkgs/profile-lib/main.rkt	39	2
profile-thunk16	/opt/racket-7.2/share/pkgs/profile-lib/main.rkt	9	0
(unnamed)	/opt/racket-7.2/collects/racket/private/more-scheme.rkt	261	28