\[\left(\left(\sqrt{\pi \cdot 2} \cdot {\left(\left(\left(z - 1\right) + 7\right) + 0.5\right)}^{\left(\left(z - 1\right) + 0.5\right)}\right) \cdot e^{-\left(\left(\left(z - 1\right) + 7\right) + 0.5\right)}\right) \cdot \left(\left(\left(\left(\left(\left(\left(\left(0.9999999999998099298181841732002794742584 + \frac{676.5203681218850988443591631948947906494}{\left(z - 1\right) + 1}\right) + \frac{-1259.139216722402807135949842631816864014}{\left(z - 1\right) + 2}\right) + \frac{771.3234287776531346025876700878143310547}{\left(z - 1\right) + 3}\right) + \frac{-176.6150291621405870046146446838974952698}{\left(z - 1\right) + 4}\right) + \frac{12.50734327868690520801919774385169148445}{\left(z - 1\right) + 5}\right) + \frac{-0.1385710952657201178173096423051902092993}{\left(z - 1\right) + 6}\right) + \frac{9.984369578019571583242346146658263705831 \cdot 10^{-6}}{\left(z - 1\right) + 7}\right) + \frac{1.505632735149311617592788074479481785772 \cdot 10^{-7}}{\left(z - 1\right) + 8}\right)\]
\left(\left(\sqrt{\pi \cdot 2} \cdot {\left(\left(\left(z - 1\right) + 7\right) + 0.5\right)}^{\left(\left(z - 1\right) + 0.5\right)}\right) \cdot e^{-\left(\left(\left(z - 1\right) + 7\right) + 0.5\right)}\right) \cdot \left(\left(\left(\left(\left(\left(\left(\left(0.9999999999998099298181841732002794742584 + \frac{676.5203681218850988443591631948947906494}{\left(z - 1\right) + 1}\right) + \frac{-1259.139216722402807135949842631816864014}{\left(z - 1\right) + 2}\right) + \frac{771.3234287776531346025876700878143310547}{\left(z - 1\right) + 3}\right) + \frac{-176.6150291621405870046146446838974952698}{\left(z - 1\right) + 4}\right) + \frac{12.50734327868690520801919774385169148445}{\left(z - 1\right) + 5}\right) + \frac{-0.1385710952657201178173096423051902092993}{\left(z - 1\right) + 6}\right) + \frac{9.984369578019571583242346146658263705831 \cdot 10^{-6}}{\left(z - 1\right) + 7}\right) + \frac{1.505632735149311617592788074479481785772 \cdot 10^{-7}}{\left(z - 1\right) + 8}\right)
double f(double z) {
        double r8665 = atan2(1.0, 0.0);
        double r8666 = 2.0;
        double r8667 = r8665 * r8666;
        double r8668 = sqrt(r8667);
        double r8669 = z;
        double r8670 = 1.0;
        double r8671 = r8669 - r8670;
        double r8672 = 7.0;
        double r8673 = r8671 + r8672;
        double r8674 = 0.5;
        double r8675 = r8673 + r8674;
        double r8676 = r8671 + r8674;
        double r8677 = pow(r8675, r8676);
        double r8678 = r8668 * r8677;
        double r8679 = -r8675;
        double r8680 = exp(r8679);
        double r8681 = r8678 * r8680;
        double r8682 = 0.9999999999998099;
        double r8683 = 676.5203681218851;
        double r8684 = r8671 + r8670;
        double r8685 = r8683 / r8684;
        double r8686 = r8682 + r8685;
        double r8687 = -1259.1392167224028;
        double r8688 = r8671 + r8666;
        double r8689 = r8687 / r8688;
        double r8690 = r8686 + r8689;
        double r8691 = 771.3234287776531;
        double r8692 = 3.0;
        double r8693 = r8671 + r8692;
        double r8694 = r8691 / r8693;
        double r8695 = r8690 + r8694;
        double r8696 = -176.6150291621406;
        double r8697 = 4.0;
        double r8698 = r8671 + r8697;
        double r8699 = r8696 / r8698;
        double r8700 = r8695 + r8699;
        double r8701 = 12.507343278686905;
        double r8702 = 5.0;
        double r8703 = r8671 + r8702;
        double r8704 = r8701 / r8703;
        double r8705 = r8700 + r8704;
        double r8706 = -0.13857109526572012;
        double r8707 = 6.0;
        double r8708 = r8671 + r8707;
        double r8709 = r8706 / r8708;
        double r8710 = r8705 + r8709;
        double r8711 = 9.984369578019572e-06;
        double r8712 = r8711 / r8673;
        double r8713 = r8710 + r8712;
        double r8714 = 1.5056327351493116e-07;
        double r8715 = 8.0;
        double r8716 = r8671 + r8715;
        double r8717 = r8714 / r8716;
        double r8718 = r8713 + r8717;
        double r8719 = r8681 * r8718;
        return r8719;
}

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2019173 
(FPCore (z)
  :name "Jmat.Real.gamma, branch z greater than 0.5"
  (* (* (* (sqrt (* PI 2.0)) (pow (+ (+ (- z 1.0) 7.0) 0.5) (+ (- z 1.0) 0.5))) (exp (- (+ (+ (- z 1.0) 7.0) 0.5)))) (+ (+ (+ (+ (+ (+ (+ (+ 0.9999999999998099 (/ 676.5203681218851 (+ (- z 1.0) 1.0))) (/ -1259.1392167224028 (+ (- z 1.0) 2.0))) (/ 771.3234287776531 (+ (- z 1.0) 3.0))) (/ -176.6150291621406 (+ (- z 1.0) 4.0))) (/ 12.507343278686905 (+ (- z 1.0) 5.0))) (/ -0.13857109526572012 (+ (- z 1.0) 6.0))) (/ 9.984369578019572e-06 (+ (- z 1.0) 7.0))) (/ 1.5056327351493116e-07 (+ (- z 1.0) 8.0)))))

Backtrace

atab-pick-alt: contract violation expected: alt? given: '(#<alt (λ (z) (* (* (+ (+ (+ (/ 9.984369578019572e-06 (+ 7.0 (- z 1.0))) 0.9999999999998099) (+ (+ (+ (/ -1259.1392167224028 (+ 2.0 (- z 1.0))) (/ 676.5203681218851 z)) (/ 771.3234287776531 (+ (- z 1.0) 3.0))) (/ -176.6150291621406 (- (+ z 4.0) 1.0)))... in: the range of the #:picking-func argument of (-> alt-table? #:only-fresh boolean? #:picking-func (-> (listof alt?) alt?) (values alt? alt-table?)) contract from: /data/pavpan/nightlies/herbie/no-costs-2/src/core/alt-table.rkt blaming: /data/pavpan/nightlies/herbie/no-costs-2/src/mainloop.rkt (assuming the contract is correct) at: /data/pavpan/nightlies/herbie/no-costs-2/src/core/alt-table.rkt:13.3LC
raise-blame-error16/opt/racket-7.0/collects/racket/contract/private/blame.rkt3470
(unnamed)/data/pavpan/nightlies/herbie/no-costs-2/src/core/alt-table.rkt590
(unnamed)/opt/racket-7.0/collects/racket/contract/private/arrow-val-first.rkt38818
choose-best-alt!/data/pavpan/nightlies/herbie/no-costs-2/src/mainloop.rkt1100
run-iter!/data/pavpan/nightlies/herbie/no-costs-2/src/mainloop.rkt3190
for-loop/data/pavpan/nightlies/herbie/no-costs-2/src/mainloop.rkt3534
run-improve43/data/pavpan/nightlies/herbie/no-costs-2/src/mainloop.rkt3380
(unnamed)/opt/racket-7.0/collects/racket/private/more-scheme.rkt26128
run/opt/racket-7.0/share/pkgs/profile-lib/main.rkt392
profile-thunk16/opt/racket-7.0/share/pkgs/profile-lib/main.rkt90
(unnamed)/opt/racket-7.0/collects/racket/private/more-scheme.rkt26128