Average Error: 61.8 → 0.3
Time: 11.6s
Precision: binary64
Cost: 320
\[0.9 \leq t \land t \leq 1.1\]
\[\left(1 + t \cdot 2 \cdot 10^{-16}\right) \cdot \left(1 + t \cdot 2 \cdot 10^{-16}\right) + \left(-1 - 2 \cdot \left(t \cdot 2 \cdot 10^{-16}\right)\right)\]
↓
\[t \cdot \left(t \cdot 3.9999999999999997 \cdot 10^{-32}\right)\]
\left(1 + t \cdot 2 \cdot 10^{-16}\right) \cdot \left(1 + t \cdot 2 \cdot 10^{-16}\right) + \left(-1 - 2 \cdot \left(t \cdot 2 \cdot 10^{-16}\right)\right)
↓
t \cdot \left(t \cdot 3.9999999999999997 \cdot 10^{-32}\right)
(FPCore (t)
 :precision binary64
 (+ (* (+ 1.0 (* t 2e-16)) (+ 1.0 (* t 2e-16))) (- -1.0 (* 2.0 (* t 2e-16)))))
↓
(FPCore (t) :precision binary64 (* t (* t 3.9999999999999997e-32)))
double code(double t) {
	return ((1.0 + (t * 2e-16)) * (1.0 + (t * 2e-16))) + (-1.0 - (2.0 * (t * 2e-16)));
}
↓
double code(double t) {
	return t * (t * 3.9999999999999997e-32);
}

Error

Bits error versus t

Try it out

Your Program's Arguments

Results

Enter valid numbers for all inputs

Target

Original61.8
Target50.6
Herbie0.3
\[\mathsf{fma}\left(1 + t \cdot 2 \cdot 10^{-16}, 1 + t \cdot 2 \cdot 10^{-16}, -1 - 2 \cdot \left(t \cdot 2 \cdot 10^{-16}\right)\right)\]
Alternative 1
Accuracy1.3
Cost768
\[\left(\sqrt[3]{t} \cdot \sqrt[3]{t}\right) \cdot \left(t \cdot \left(\sqrt[3]{t} \cdot 3.9999999999999997 \cdot 10^{-32}\right)\right)\]
Alternative 2
Accuracy2.1
Cost1024
\[t \cdot \left(\sqrt[3]{t \cdot 3.9999999999999997 \cdot 10^{-32}} \cdot \left(\sqrt[3]{t \cdot 3.9999999999999997 \cdot 10^{-32}} \cdot \sqrt[3]{t \cdot 3.9999999999999997 \cdot 10^{-32}}\right)\right)\]

Derivation

  1. Initial program 61.8

    \[\left(1 + t \cdot 2 \cdot 10^{-16}\right) \cdot \left(1 + t \cdot 2 \cdot 10^{-16}\right) + \left(-1 - 2 \cdot \left(t \cdot 2 \cdot 10^{-16}\right)\right)\]

  2. Simplified0.3

    \[\leadsto \color{blue}{t \cdot \left(t \cdot 3.9999999999999997 \cdot 10^{-32}\right)}\]
  3. Using strategy rm

  4. Applied pow1_binary64_25260.3

    \[\leadsto t \cdot \left(t \cdot \color{blue}{{\left( 3.9999999999999997 \cdot 10^{-32} \right)}^{1}}\right)\]

  5. Applied pow1_binary64_25260.3

    \[\leadsto t \cdot \left(\color{blue}{{t}^{1}} \cdot {\left( 3.9999999999999997 \cdot 10^{-32} \right)}^{1}\right)\]

  6. Applied pow-prod-down_binary64_25360.3

    \[\leadsto t \cdot \color{blue}{{\left(t \cdot 3.9999999999999997 \cdot 10^{-32}\right)}^{1}}\]

  7. Final simplification0.3

    \[\leadsto t \cdot \left(t \cdot 3.9999999999999997 \cdot 10^{-32}\right)\]

Reproduce

herbie shell --seed 2020322 
(FPCore (t)
  :name "fma_test1"
  :precision binary64
  :pre (<= 0.9 t 1.1)

  :herbie-target
  (fma (+ 1.0 (* t 2e-16)) (+ 1.0 (* t 2e-16)) (- -1.0 (* 2.0 (* t 2e-16))))

  (+ (* (+ 1.0 (* t 2e-16)) (+ 1.0 (* t 2e-16))) (- -1.0 (* 2.0 (* t 2e-16)))))