\[\left|\frac{1}{\sqrt{\pi}} \cdot \left(\left(\left(2 \cdot \left|x\right| + \frac{2}{3} \cdot \left(\left(\left|x\right| \cdot \left|x\right|\right) \cdot \left|x\right|\right)\right) + \frac{1}{5} \cdot \left(\left(\left(\left(\left|x\right| \cdot \left|x\right|\right) \cdot \left|x\right|\right) \cdot \left|x\right|\right) \cdot \left|x\right|\right)\right) + \frac{1}{21} \cdot \left(\left(\left(\left(\left(\left(\left|x\right| \cdot \left|x\right|\right) \cdot \left|x\right|\right) \cdot \left|x\right|\right) \cdot \left|x\right|\right) \cdot \left|x\right|\right) \cdot \left|x\right|\right)\right)\right|\]
\left|\frac{1}{\sqrt{\pi}} \cdot \left(\left(\left(2 \cdot \left|x\right| + \frac{2}{3} \cdot \left(\left(\left|x\right| \cdot \left|x\right|\right) \cdot \left|x\right|\right)\right) + \frac{1}{5} \cdot \left(\left(\left(\left(\left|x\right| \cdot \left|x\right|\right) \cdot \left|x\right|\right) \cdot \left|x\right|\right) \cdot \left|x\right|\right)\right) + \frac{1}{21} \cdot \left(\left(\left(\left(\left(\left(\left|x\right| \cdot \left|x\right|\right) \cdot \left|x\right|\right) \cdot \left|x\right|\right) \cdot \left|x\right|\right) \cdot \left|x\right|\right) \cdot \left|x\right|\right)\right)\right|
double f(double x) {
        double r84929 = 1.0;
        double r84930 = atan2(1.0, 0.0);
        double r84931 = sqrt(r84930);
        double r84932 = r84929 / r84931;
        double r84933 = 2.0;
        double r84934 = x;
        double r84935 = fabs(r84934);
        double r84936 = r84933 * r84935;
        double r84937 = 3.0;
        double r84938 = r84933 / r84937;
        double r84939 = r84935 * r84935;
        double r84940 = r84939 * r84935;
        double r84941 = r84938 * r84940;
        double r84942 = r84936 + r84941;
        double r84943 = 5.0;
        double r84944 = r84929 / r84943;
        double r84945 = r84940 * r84935;
        double r84946 = r84945 * r84935;
        double r84947 = r84944 * r84946;
        double r84948 = r84942 + r84947;
        double r84949 = 21.0;
        double r84950 = r84929 / r84949;
        double r84951 = r84946 * r84935;
        double r84952 = r84951 * r84935;
        double r84953 = r84950 * r84952;
        double r84954 = r84948 + r84953;
        double r84955 = r84932 * r84954;
        double r84956 = fabs(r84955);
        return r84956;
}

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2019194 
(FPCore (x)
  :name "Jmat.Real.erfi, branch x less than or equal to 0.5"
  (fabs (* (/ 1.0 (sqrt PI)) (+ (+ (+ (* 2.0 (fabs x)) (* (/ 2.0 3.0) (* (* (fabs x) (fabs x)) (fabs x)))) (* (/ 1.0 5.0) (* (* (* (* (fabs x) (fabs x)) (fabs x)) (fabs x)) (fabs x)))) (* (/ 1.0 21.0) (* (* (* (* (* (* (fabs x) (fabs x)) (fabs x)) (fabs x)) (fabs x)) (fabs x)) (fabs x)))))))

Backtrace

get-representation: Unknown representation #fLC
(unnamed)/data/pavpan/nightlies/herbie/js-tweaks/src/core/localize.rkt2313
hash-ref!/opt/racket-7.0/collects/racket/private/more-scheme.rkt3762
map/opt/racket-7.0/collects/racket/private/map.rkt3513
parse-loop30/opt/racket-7.0/collects/racket/match/compiler.rkt41815
hash-ref!/opt/racket-7.0/collects/racket/private/more-scheme.rkt3762
map/opt/racket-7.0/collects/racket/private/map.rkt3513
parse-loop30/opt/racket-7.0/collects/racket/match/compiler.rkt41815
hash-ref!/opt/racket-7.0/collects/racket/private/more-scheme.rkt3762
map/opt/racket-7.0/collects/racket/private/map.rkt3513
parse-loop30/opt/racket-7.0/collects/racket/match/compiler.rkt41815
hash-ref!/opt/racket-7.0/collects/racket/private/more-scheme.rkt3762
map/opt/racket-7.0/collects/racket/private/map.rkt3513
parse-loop30/opt/racket-7.0/collects/racket/match/compiler.rkt41815
hash-ref!/opt/racket-7.0/collects/racket/private/more-scheme.rkt3762
localize-error/data/pavpan/nightlies/herbie/js-tweaks/src/core/localize.rkt610
localize!/data/pavpan/nightlies/herbie/js-tweaks/src/mainloop.rkt1230
run-iter!/data/pavpan/nightlies/herbie/js-tweaks/src/mainloop.rkt3230
for-loop/data/pavpan/nightlies/herbie/js-tweaks/src/mainloop.rkt3594
run-improve47/data/pavpan/nightlies/herbie/js-tweaks/src/mainloop.rkt3420
(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