diff --git a/notes/sections/2.md b/notes/sections/2.md index c6759a2..9281c1a 100644 --- a/notes/sections/2.md +++ b/notes/sections/2.md @@ -43,44 +43,50 @@ $$ | \gamma(n_{i+1}) - \gamma | > | \gamma(n_i) - \gamma| $$ -and $\gamma (n_i)$ was selected as the result (see @tbl:1_results). +and $\gamma (n_i)$ was selected as the best result (see @tbl:1_results). ------------------------------------------------ -n sum $|\gamma(n)-\gamma|$ ------------ ------------- --------------------- -\SI{2e1}{} \SI{2.48e-02}{} +--------------------------------- +n $|\gamma(n)-\gamma|$ +----------- --------------------- +\SI{2e1}{} \SI{2.48e-02}{} -\SI{2e2}{} \SI{2.50e-03}{} +\SI{2e2}{} \SI{2.50e-03}{} -\SI{2e3}{} \SI{2.50e-04}{} +\SI{2e3}{} \SI{2.50e-04}{} -\SI{2e4}{} \SI{2.50e-05}{} +\SI{2e4}{} \SI{2.50e-05}{} -\SI{2e5}{} \SI{2.50e-06}{} +\SI{2e5}{} \SI{2.50e-06}{} -\SI{2e6}{} \SI{2.50e-07}{} +\SI{2e6}{} \SI{2.50e-07}{} -\SI{2e7}{} \SI{2.50e-08}{} +\SI{2e7}{} \SI{2.50e-08}{} -\SI{2e8}{} \SI{2.50e-09}{} +\SI{2e8}{} \SI{2.50e-09}{} -\SI{2e9}{} \SI{2.55e-10}{} +\SI{2e9}{} \SI{2.55e-10}{} -\SI{2e10}{} \SI{2.42e-11}{} +\SI{2e10}{} \SI{2.42e-11}{} -\SI{2e11}{} \SI{1.44e-08}{} ------------------------------------------------ +\SI{2e11}{} \SI{1.44e-08}{} +--------------------------------- Table: Partial results using the definition of $\gamma$ with double precision. {#tbl:1_results} The convergence is logarithmic: to fix the first $d$ decimal places, about -$10^d$ terms are needed. The double precision runs out at the -10\textsuperscript{th} place, $n=\SI{2e10}{}$. -Since all the number are given with double precision, there can be at best 15 -correct digits but only 10 were correctly computed: this means that when the -terms of the series start being smaller than the smallest representable double, -the sum of all the remaining terms give a number $\propto 10^{-11}$. +$10^d$ terms of the armonic series are needed. The double precision runs out at +the $10^{\text{th}}$ place, at $n=\SI{2e10}{}$. +Since all the number are given with double precision, there can be at best 16 +correct digits, since for a double 64 bits are allocated in memory: 1 for the +sign, 8 for the exponent and 55 for the mantissa: +$$ + 2^{55} = 10^{d} \thus d = 55 \cdot \log(2) \sim 16.6 +$$ + +Only 10 digits were correctly computed: this means that when the terms of the +series start being smaller than the smallest representable double, the sum of +all the remaining terms gives a number $\propto 10^{-11}$. Best result in @tbl:first. --------- ----------------------- @@ -106,7 +112,7 @@ $$ Varying $M$ from 1 to 100, the best result was obtained for $M = 41$ (see @tbl:second). It went sour: the convergence is worse than using the definition -itself. Only two places were correctly computed (#@tbl:second). +itself. Only two places were correctly computed (@tbl:second). --------- ----------------------- true: 0.57721\ 56649\ 01533