\[\left(\left(\left(\sqrt{x + 1} - \sqrt{x}\right) + \left(\sqrt{y + 1} - \sqrt{y}\right)\right) + \left(\sqrt{z + 1} - \sqrt{z}\right)\right) + \left(\sqrt{t + 1} - \sqrt{t}\right)\]

\left(\left(\left(\sqrt{x + 1} - \sqrt{x}\right) + \left(\sqrt{y + 1} - \sqrt{y}\right)\right) + \left(\sqrt{z + 1} - \sqrt{z}\right)\right) + \left(\sqrt{t + 1} - \sqrt{t}\right)

double f(double x, double y, double z, double t) {
        double r95371 = x;
        double r95372 = 1.0;
        double r95373 = r95371 + r95372;
        double r95374 = sqrt(r95373);
        double r95375 = sqrt(r95371);
        double r95376 = r95374 - r95375;
        double r95377 = y;
        double r95378 = r95377 + r95372;
        double r95379 = sqrt(r95378);
        double r95380 = sqrt(r95377);
        double r95381 = r95379 - r95380;
        double r95382 = r95376 + r95381;
        double r95383 = z;
        double r95384 = r95383 + r95372;
        double r95385 = sqrt(r95384);
        double r95386 = sqrt(r95383);
        double r95387 = r95385 - r95386;
        double r95388 = r95382 + r95387;
        double r95389 = t;
        double r95390 = r95389 + r95372;
        double r95391 = sqrt(r95390);
        double r95392 = sqrt(r95389);
        double r95393 = r95391 - r95392;
        double r95394 = r95388 + r95393;
        return r95394;
}

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2020045 +o rules:numerics
(FPCore (x y z t)
  :name "Main:z from "
  :precision binary64

  :herbie-target
  (+ (+ (+ (/ 1 (+ (sqrt (+ x 1)) (sqrt x))) (/ 1 (+ (sqrt (+ y 1)) (sqrt y)))) (/ 1 (+ (sqrt (+ z 1)) (sqrt z)))) (- (sqrt (+ t 1)) (sqrt t)))

  (+ (+ (+ (- (sqrt (+ x 1)) (sqrt x)) (- (sqrt (+ y 1)) (sqrt y))) (- (sqrt (+ z 1)) (sqrt z))) (- (sqrt (+ t 1)) (sqrt t))))

Backtrace

hash-ref: no value found for key key: '(* #<enode 91(108)> #<enode 140(140)>)		L	C
for-loop	/data/pavpan/nightlies/herbie/simplify-regraph-rebuilding/regraph/egraph.rkt	270	6
update-leader!	/data/pavpan/nightlies/herbie/simplify-regraph-rebuilding/regraph/egraph.rkt	265	0
for-loop	/data/pavpan/nightlies/herbie/simplify-regraph-rebuilding/regraph/main.rkt	77	2
prune-phase	/data/pavpan/nightlies/herbie/simplify-regraph-rebuilding/regraph/main.rkt	74	0
for-loop	/data/pavpan/nightlies/herbie/simplify-upwards-no-duplicates/src/core/simplify.rkt	80	4
for-loop	/data/pavpan/nightlies/herbie/simplify-upwards-no-duplicates/src/core/simplify.rkt	76	2
(unnamed)	/data/pavpan/nightlies/herbie/simplify-upwards-no-duplicates/src/core/simplify.rkt	56	0
(unnamed)	/data/pavpan/nightlies/herbie/simplify-upwards-no-duplicates/src/core/simplify.rkt	38	0
simplify!	/data/pavpan/nightlies/herbie/simplify-upwards-no-duplicates/src/mainloop.rkt	224	0
run-iter!	/data/pavpan/nightlies/herbie/simplify-upwards-no-duplicates/src/mainloop.rkt	327	0
for-loop	/data/pavpan/nightlies/herbie/simplify-upwards-no-duplicates/src/mainloop.rkt	365	4
run-improve47	/data/pavpan/nightlies/herbie/simplify-upwards-no-duplicates/src/mainloop.rkt	346	0
.../more-scheme.rkt:261:28	unknown
run	/opt/racket-7.5/share/pkgs/profile-lib/main.rkt	39	2
profile-thunk16	/opt/racket-7.5/share/pkgs/profile-lib/main.rkt	9	0
(unnamed)	/opt/racket-7.5/collects/racket/private/more-scheme.rkt	261	28

Falling back on racket egraph because egg-herbie package not installed (more)

Reproduce

Backtrace