\[\log \left(N + 1\right) - \log N\]
Test:
NMSE problem 3.3.6
Bits:
128 bits
Bits error versus N
Time: 18.8 s
Input Error: 40.2
Output Error: 19.4
Log:
\(\begin{cases} \log \left(\frac{N + 1}{N}\right) & \text{when } N \le 519383.0646430557 \\ \frac{\frac{\frac{1}{3}}{N} - \frac{1}{2}}{{N}^2} + \frac{1}{N} & \text{otherwise} \end{cases}\)

    if N < 519383.0646430557

    1. Started with
      \[\log \left(N + 1\right) - \log N\]
      30.9
    2. Using strategy rm
      30.9
    3. Applied diff-log to get
      \[\color{red}{\log \left(N + 1\right) - \log N} \leadsto \color{blue}{\log \left(\frac{N + 1}{N}\right)}\]
      28.6

    if 519383.0646430557 < N

    1. Started with
      \[\log \left(N + 1\right) - \log N\]
      59.7
    2. Applied taylor to get
      \[\log \left(N + 1\right) - \log N \leadsto \left(\frac{1}{3} \cdot \frac{1}{{N}^{3}} + \frac{1}{N}\right) - \frac{1}{2} \cdot \frac{1}{{N}^2}\]
      0.0
    3. Taylor expanded around inf to get
      \[\color{red}{\left(\frac{1}{3} \cdot \frac{1}{{N}^{3}} + \frac{1}{N}\right) - \frac{1}{2} \cdot \frac{1}{{N}^2}} \leadsto \color{blue}{\left(\frac{1}{3} \cdot \frac{1}{{N}^{3}} + \frac{1}{N}\right) - \frac{1}{2} \cdot \frac{1}{{N}^2}}\]
      0.0
    4. Applied simplify to get
      \[\color{red}{\left(\frac{1}{3} \cdot \frac{1}{{N}^{3}} + \frac{1}{N}\right) - \frac{1}{2} \cdot \frac{1}{{N}^2}} \leadsto \color{blue}{\frac{\frac{1}{N}}{N} \cdot \left(\frac{\frac{1}{3}}{N} - \frac{1}{2}\right) + \frac{1}{N}}\]
      0.0
    5. Applied simplify to get
      \[\color{red}{\frac{\frac{1}{N}}{N} \cdot \left(\frac{\frac{1}{3}}{N} - \frac{1}{2}\right)} + \frac{1}{N} \leadsto \color{blue}{\frac{\frac{\frac{1}{3}}{N} - \frac{1}{2}}{{N}^2}} + \frac{1}{N}\]
      0.0

  1. Removed slow pow expressions

Original test:


(lambda ((N default))
  #:name "NMSE problem 3.3.6"
  (- (log (+ N 1)) (log N)))