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Re: Generalised bisection

From
EWEaldwulf Wuffinga <ealdwulf@googlemail.com>
Date
Mar 13, 2009, 09:58 UTC
Message-ID
<efe2b6d70903130258t2594b027m5812e9a5895f477e@mail.gmail.com>
In-Reply-To
<43d8ce650903112345x3d40b70ap7e4c0f8c7d0b6069@mail.gmail.com>
On Thu, Mar 12, 2009 at 6:45 AM, John Tapsell <johnflux@gmail.com> wrote:
Show 8 quoted lines
> 2009/3/11 Ealdwulf Wuffinga <ealdwulf@googlemail.com>:
>> On Wed, Mar 11, 2009 at 9:35 AM, John Tapsell <johnflux@gmail.com> wrote:
>> What I use is the multiprecision floating point number class. doubles
>> don't seem to be long enough.
>
> Hmm, really really?  Sometimes this sort of thing can be fixed by just
> readjusting the formulas.  What formulas are you using that require
> more precision than doubles?

I'll have to reply to this later when I have more time. However, there is a (rather verbose) file in the doc directory which describes them - in texmacs format, but I've just uploaded a pdf version as well. It is BayesianSearch_Debugging.pdf. The description of this code starts in section 2.2 (since I wrote that, I have generalised it to the DAG case as in git).

Show 11 quoted lines
> A little bit of math trickery helps here :-)
>
> y =  x^b
>
> log(y) = log(x^b) = b * log(x)
> e^log(y) = e^(b log(x))
>
> y = exp(b * log(x))
>
> So as long as you have 'exp' and 'log' functions, you can raise x to
> the power of b, even if b is fractional.

Sadly gmp does not have log or exp. mpfr does, but it does not have a python interface.

Alex
Previous: Ealdwulf WuffingaNext: Johannes Schindelin
Message 22 of 25 in “Generalised bisection”
  1. Ealdwulf WuffingaMar 9, 2009
  2. Christian CouderMar 10, 2009
  3. Ealdwulf WuffingaMar 11, 2009
  4. John TapsellMar 11, 2009
  5. Johannes SchindelinMar 11, 2009
  6. John TapsellMar 11, 2009
  7. Johannes SchindelinMar 11, 2009
  8. John TapsellMar 11, 2009
  9. Ealdwulf WuffingaMar 11, 2009
  10. Ealdwulf WuffingaMar 11, 2009
  11. John TapsellMar 12, 2009
  12. Johannes SchindelinMar 12, 2009
  13. Steven TweedMar 12, 2009
  14. Ealdwulf WuffingaMar 13, 2009
  15. Ealdwulf WuffingaMar 13, 2009
  16. Steven TweedMar 13, 2009
  17. Ealdwulf WuffingaMar 15, 2009
  18. Steven TweedMar 16, 2009
  19. John TapsellMar 16, 2009
  20. Ealdwulf WuffingaMar 16, 2009
  21. Ealdwulf WuffingaMar 16, 2009
  22. Ealdwulf WuffingaMar 13, 2009
  23. Johannes SchindelinMar 13, 2009
  24. John TapsellMar 13, 2009
  25. Johannes SchindelinMar 13, 2009

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