Average Error: 59.9 → 0.3
Time: 21.7s
Precision: 64
Internal Precision: 128
\[\frac{1}{x} - \frac{1}{\tan x}\]
↓
\[\frac{1}{3} \cdot x + \left({x}^{5} \cdot \frac{2}{945} + \frac{1}{45} \cdot {x}^{3}\right)\]

Error

Bits error versus x

Try it out

Your Program's Arguments

Results

Enter valid numbers for all inputs

Target

Original59.9
Target0.1
Herbie0.3
\[\begin{array}{l} \mathbf{if}\;\left|x\right| \lt 0.026:\\ \;\;\;\;\frac{x}{3} \cdot \left(1 + \frac{x \cdot x}{15}\right)\\ \mathbf{else}:\\ \;\;\;\;\frac{1}{x} - \frac{1}{\tan x}\\ \end{array}\]

Derivation

  1. Initial program 59.9

    \[\frac{1}{x} - \frac{1}{\tan x}\]

  2. Taylor expanded around 0 0.3

    \[\leadsto \color{blue}{\frac{1}{3} \cdot x + \left(\frac{1}{45} \cdot {x}^{3} + \frac{2}{945} \cdot {x}^{5}\right)}\]

  3. Final simplification0.3

    \[\leadsto \frac{1}{3} \cdot x + \left({x}^{5} \cdot \frac{2}{945} + \frac{1}{45} \cdot {x}^{3}\right)\]

Reproduce

herbie shell --seed 2019010 
(FPCore (x)
  :name "invcot (example 3.9)"
  :pre (and (< -0.026 x) (< x 0.026))

  :herbie-target
  (if (< (fabs x) 0.026) (* (/ x 3) (+ 1 (/ (* x x) 15))) (- (/ 1 x) (/ 1 (tan x))))

  (- (/ 1 x) (/ 1 (tan x))))

Details

Time bar (total: 20.4s)Debug log

sample486.0ms

Algorithm
intervals

simplify5.0ms

Counts
1 → 1
Calls
1 calls:
Slowest
5.0ms
(- (/ 1 x) (/ 1 (tan x)))

prune8.0ms

Pruning

1 alts after pruning (1 fresh and 0 done)

Merged error: 60.2b

localize24.0ms

Local error

Found 1 expressions with local error:

2.1b
(- (/ 1 x) (/ 1 (tan x)))

rewrite9.0ms

Algorithm
rewrite-expression-head
Rules
5×*-un-lft-identity
4×distribute-lft-out--
4×div-inv
3×add-log-exp
3×add-sqr-sqrt
1×difference-of-squares
1×flip--
1×add-cube-cbrt
1×frac-sub
1×add-exp-log
1×diff-log
1×add-cbrt-cube
1×flip3--
1×sub-neg
1×pow1
Counts
1 → 18
Calls
1 calls:
Slowest
8.0ms
(- (/ 1 x) (/ 1 (tan x)))

series81.0ms

Counts
1 → 3
Calls
1 calls:
Slowest
81.0ms
(- (/ 1 x) (/ 1 (tan x)))

simplify119.0ms

Counts
12 → 21
Calls
12 calls:
Slowest
35.0ms
(+ (* 1/3 x) (+ (* 1/45 (pow x 3)) (* 2/945 (pow x 5))))
15.0ms
(/ (exp (/ 1 x)) (exp (/ 1 (tan x))))
11.0ms
(- (/ 1 x) (/ 1 (tan x)))
11.0ms
(- (/ 1 x) (/ (cos x) (sin x)))
10.0ms
(- (/ 1 x) (/ (cos x) (sin x)))

prune170.0ms

Pruning

1 alts after pruning (1 fresh and 0 done)

Merged error: 0.4b

localize41.0ms

Local error

Found 4 expressions with local error:

0.4b
(* 1/3 x)
0.1b
(* 1/45 (pow x 3))
0.1b
(* 2/945 (pow x 5))
0.0b
(+ (* 1/45 (pow x 3)) (* 2/945 (pow x 5)))

rewrite13.0ms

Algorithm
rewrite-expression-head
Rules
8×associate-*r*
6×add-log-exp
6×add-cube-cbrt
6×*-un-lft-identity
6×add-sqr-sqrt
4×add-exp-log
4×add-cbrt-cube
4×pow1
3×*-commutative
1×flip-+
1×unpow3
1×flip3-+
1×sum-log
1×+-commutative
1×cube-mult
Counts
4 → 43
Calls
4 calls:
Slowest
6.0ms
(+ (* 1/45 (pow x 3)) (* 2/945 (pow x 5)))
3.0ms
(* 1/45 (pow x 3))
2.0ms
(* 2/945 (pow x 5))
0.0ms
(* 1/3 x)

series172.0ms

Counts
4 → 12
Calls
4 calls:
Slowest
90.0ms
(+ (* 1/45 (pow x 3)) (* 2/945 (pow x 5)))
39.0ms
(* 2/945 (pow x 5))
30.0ms
(* 1/45 (pow x 3))
13.0ms
(* 1/3 x)

simplify151.0ms

Counts
20 → 55
Calls
20 calls:
Slowest
25.0ms
(+ (* 1/45 (pow x 3)) (* 2/945 (pow x 5)))
24.0ms
(+ (* 1/45 (pow x 3)) (* 2/945 (pow x 5)))
23.0ms
(+ (* 1/45 (pow x 3)) (* 2/945 (pow x 5)))
22.0ms
(* (exp (* 1/45 (pow x 3))) (exp (* 2/945 (pow x 5))))
10.0ms
(* 1/45 (pow x 3))

prune535.0ms

Pruning

4 alts after pruning (3 fresh and 1 done)

Merged error: 0.3b

localize26.0ms

Local error

Found 4 expressions with local error:

0.6b
(cbrt (* 1/3 x))
0.6b
(cbrt (* 1/3 x))
0.6b
(cbrt (* 1/3 x))
0.5b
(* (cbrt (* 1/3 x)) (cbrt (* 1/3 x)))

rewrite6.0ms

Algorithm
rewrite-expression-head
Rules
9×pow1
7×pow1/3
6×add-cube-cbrt
6×add-exp-log
6×*-un-lft-identity
6×add-sqr-sqrt
5×cbrt-prod
4×add-log-exp
4×associate-*l*
4×associate-*r*
4×add-cbrt-cube
2×pow-prod-up
2×pow-prod-down
1×cbrt-unprod
1×*-commutative
1×prod-exp
1×pow-plus
1×pow2
Counts
4 → 51
Calls
4 calls:
Slowest
4.0ms
(* (cbrt (* 1/3 x)) (cbrt (* 1/3 x)))
1.0ms
(cbrt (* 1/3 x))
0.0ms
(cbrt (* 1/3 x))
0.0ms
(cbrt (* 1/3 x))

series1.4s

Counts
4 → 12
Calls
4 calls:
Slowest
357.0ms
(cbrt (* 1/3 x))
356.0ms
(cbrt (* 1/3 x))
350.0ms
(* (cbrt (* 1/3 x)) (cbrt (* 1/3 x)))
315.0ms
(cbrt (* 1/3 x))

simplify145.0ms

Counts
31 → 63
Calls
31 calls:
Slowest
16.0ms
(* (* 1/3 x) (* 1/3 x))
12.0ms
(* (cbrt -1/3) (pow (* x -1) 1/3))
11.0ms
(* (pow (cbrt 1/3) 2) (pow (pow x 2) 1/3))
10.0ms
(* (cbrt -1/3) (pow (* x -1) 1/3))
9.0ms
(* (pow (cbrt -1/3) 2) (pow (pow x 2) 1/3))

prune733.0ms

Pruning

11 alts after pruning (10 fresh and 1 done)

Merged error: 0.2b

localize28.0ms

Local error

Found 4 expressions with local error:

0.7b
(cbrt x)
0.6b
(cbrt (* 1/3 x))
0.6b
(cbrt (* 1/3 x))
0.4b
(* (cbrt 1/3) (* (cbrt x) (cbrt (* 1/3 x))))

rewrite14.0ms

Algorithm
rewrite-expression-head
Rules
9×add-exp-log
9×pow1
6×pow1/3
5×add-cube-cbrt
5×pow-prod-down
5×add-cbrt-cube
5×*-un-lft-identity
5×add-sqr-sqrt
4×add-log-exp
3×cbrt-unprod
3×prod-exp
3×associate-*l*
2×cbrt-prod
1×*-commutative
1×associate-*r*
Counts
4 → 45
Calls
4 calls:
Slowest
13.0ms
(* (cbrt 1/3) (* (cbrt x) (cbrt (* 1/3 x))))
0.0ms
(cbrt (* 1/3 x))
0.0ms
(cbrt (* 1/3 x))
0.0ms
(cbrt x)

series1.5s

Counts
4 → 12
Calls
4 calls:
Slowest
492.0ms
(* (cbrt 1/3) (* (cbrt x) (cbrt (* 1/3 x))))
371.0ms
(cbrt (* 1/3 x))
314.0ms
(cbrt x)
306.0ms
(cbrt (* 1/3 x))

simplify542.0ms

Counts
24 → 57
Calls
24 calls:
Slowest
328.0ms
(* 1/3 (* (* (* (cbrt x) (cbrt (* 1/3 x))) (* (cbrt x) (cbrt (* 1/3 x)))) (* (cbrt x) (cbrt (* 1/3 x)))))
59.0ms
(* (* (cbrt -1/3) (* (cbrt 1/3) (cbrt -1))) (pow (pow x 2) 1/3))
20.0ms
(* 1/3 (* x (* 1/3 x)))
20.0ms
(* (cbrt 1/3) (* (cbrt x) (cbrt (* 1/3 x))))
14.0ms
(* (cbrt 1/3) (* (cbrt x) (cbrt (* 1/3 x))))

prune599.0ms

Pruning

12 alts after pruning (11 fresh and 1 done)

Merged error: 0.1b

regimes99.0ms

Accuracy

0% (0.2b remaining)

Error of 0.3b against oracle of 0.2b and baseline of 0.3b

bsearch3.0ms

end0.0ms

sample13.5s

Algorithm
intervals