\[\left|\frac{1}{\sqrt{\pi}} \cdot \left(\left(\left(2 \cdot \left|x\right| + \frac{2}{3} \cdot \left(\left(\left|x\right| \cdot \left|x\right|\right) \cdot \left|x\right|\right)\right) + \frac{1}{5} \cdot \left(\left(\left(\left(\left|x\right| \cdot \left|x\right|\right) \cdot \left|x\right|\right) \cdot \left|x\right|\right) \cdot \left|x\right|\right)\right) + \frac{1}{21} \cdot \left(\left(\left(\left(\left(\left(\left|x\right| \cdot \left|x\right|\right) \cdot \left|x\right|\right) \cdot \left|x\right|\right) \cdot \left|x\right|\right) \cdot \left|x\right|\right) \cdot \left|x\right|\right)\right)\right|\]
\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 r79472 = 1.0;
        double r79473 = atan2(1.0, 0.0);
        double r79474 = sqrt(r79473);
        double r79475 = r79472 / r79474;
        double r79476 = 2.0;
        double r79477 = x;
        double r79478 = fabs(r79477);
        double r79479 = r79476 * r79478;
        double r79480 = 3.0;
        double r79481 = r79476 / r79480;
        double r79482 = r79478 * r79478;
        double r79483 = r79482 * r79478;
        double r79484 = r79481 * r79483;
        double r79485 = r79479 + r79484;
        double r79486 = 5.0;
        double r79487 = r79472 / r79486;
        double r79488 = r79483 * r79478;
        double r79489 = r79488 * r79478;
        double r79490 = r79487 * r79489;
        double r79491 = r79485 + r79490;
        double r79492 = 21.0;
        double r79493 = r79472 / r79492;
        double r79494 = r79489 * r79478;
        double r79495 = r79494 * r79478;
        double r79496 = r79493 * r79495;
        double r79497 = r79491 + r79496;
        double r79498 = r79475 * r79497;
        double r79499 = fabs(r79498);
        return r79499;
}

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2019194 +o rules:numerics
(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/master/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/master/src/core/localize.rkt610
localize!/data/pavpan/nightlies/herbie/master/src/mainloop.rkt1230
run-iter!/data/pavpan/nightlies/herbie/master/src/mainloop.rkt3230
for-loop/data/pavpan/nightlies/herbie/master/src/mainloop.rkt3594
run-improve47/data/pavpan/nightlies/herbie/master/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