\[\frac{\left(-b/2\right) - \sqrt{{b/2}^2 - a \cdot c}}{a}\]
Test:
NMSE problem 3.2.1, negative
Bits:
128 bits
Bits error versus a
Bits error versus b/2
Bits error versus c
Time: 15.2 s
Input Error: 18.0
Output Error: 2.3
Log: ⚲
Profile: 🕒
\(\begin{cases} \frac{c}{\frac{b/2}{\frac{-1}{2}}} & \text{when } b/2 \le -1.4516784f-11 \\ \frac{{\left(\left(-b/2\right) - \sqrt{{b/2}^2 - a \cdot c}\right)}^{1}}{a} & \text{when } b/2 \le 1.6024659f+18 \\ \frac{\frac{1}{2}}{\frac{b/2}{c}} - \frac{b/2}{a} \cdot 2 & \text{otherwise} \end{cases}\)

    if b/2 < -1.4516784f-11

    1. Started with
      \[\frac{\left(-b/2\right) - \sqrt{{b/2}^2 - a \cdot c}}{a}\]
      28.1
    2. Using strategy rm
      28.1
    3. Applied pow1 to get
      \[\frac{\color{red}{\left(-b/2\right) - \sqrt{{b/2}^2 - a \cdot c}}}{a} \leadsto \frac{\color{blue}{{\left(\left(-b/2\right) - \sqrt{{b/2}^2 - a \cdot c}\right)}^{1}}}{a}\]
      28.1
    4. Applied taylor to get
      \[\frac{{\left(\left(-b/2\right) - \sqrt{{b/2}^2 - a \cdot c}\right)}^{1}}{a} \leadsto \frac{{\left(\frac{-1}{2} \cdot \frac{c \cdot a}{b/2}\right)}^{1}}{a}\]
      7.1
    5. Taylor expanded around -inf to get
      \[\frac{{\color{red}{\left(\frac{-1}{2} \cdot \frac{c \cdot a}{b/2}\right)}}^{1}}{a} \leadsto \frac{{\color{blue}{\left(\frac{-1}{2} \cdot \frac{c \cdot a}{b/2}\right)}}^{1}}{a}\]
      7.1
    6. Applied simplify to get
      \[\color{red}{\frac{{\left(\frac{-1}{2} \cdot \frac{c \cdot a}{b/2}\right)}^{1}}{a}} \leadsto \color{blue}{\frac{c}{\frac{b/2}{\frac{-1}{2}}}}\]
      0.1

    if -1.4516784f-11 < b/2 < 1.6024659f+18

    1. Started with
      \[\frac{\left(-b/2\right) - \sqrt{{b/2}^2 - a \cdot c}}{a}\]
      5.2
    2. Using strategy rm
      5.2
    3. Applied pow1 to get
      \[\frac{\color{red}{\left(-b/2\right) - \sqrt{{b/2}^2 - a \cdot c}}}{a} \leadsto \frac{\color{blue}{{\left(\left(-b/2\right) - \sqrt{{b/2}^2 - a \cdot c}\right)}^{1}}}{a}\]
      5.2

    if 1.6024659f+18 < b/2

    1. Started with
      \[\frac{\left(-b/2\right) - \sqrt{{b/2}^2 - a \cdot c}}{a}\]
      27.6
    2. Applied taylor to get
      \[\frac{\left(-b/2\right) - \sqrt{{b/2}^2 - a \cdot c}}{a} \leadsto \frac{\frac{1}{2} \cdot \frac{c \cdot a}{b/2} - 2 \cdot b/2}{a}\]
      5.9
    3. Taylor expanded around inf to get
      \[\frac{\color{red}{\frac{1}{2} \cdot \frac{c \cdot a}{b/2} - 2 \cdot b/2}}{a} \leadsto \frac{\color{blue}{\frac{1}{2} \cdot \frac{c \cdot a}{b/2} - 2 \cdot b/2}}{a}\]
      5.9
    4. Applied simplify to get
      \[\color{red}{\frac{\frac{1}{2} \cdot \frac{c \cdot a}{b/2} - 2 \cdot b/2}{a}} \leadsto \color{blue}{\frac{\frac{1}{2}}{\frac{b/2}{c}} - \frac{b/2}{a} \cdot 2}\]
      0.0
  1. Removed slow pow expressions

Original test:


(lambda ((a default) (b/2 default) (c default))
  #:name "NMSE problem 3.2.1, negative"
  (/ (- (- b/2) (sqrt (- (sqr b/2) (* a c)))) a))