Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
Precision check on [] SOLVED
(06/28/2011, 07:17 AM)Cherrina_Pixie Wrote: ....
I ran through the loops for <sexp> of base ~4.81 and somehow, the indeterminacy of the 13th loop exceeded that of the 12th loop. Is there a way to solve this issue without changing the base? I'm not exactly certain about the possible consequences of this, other than the likely limit of precision... is a result like this 'normal' for larger bases?
The problem is with the tetration/sexp code (which is used by I haven't seen this bug before in, despite having tried a large number of different bases from 1.45 to 100,000 or so. But this particular base, exp(pi/2), seems to be a problem. I don't yet know why. Although in earlier versions of I saw it when pari-gp wasn't carrying out calculations with enough precision -- although I've fixed all of those bugs by manually updating the precision for the samples used to generate theta(z).

I tried a few things, but this particular base seems to stop converging around 80 or 90 binary bits of precision (depending on which algorithm I use). I don't understand it yet, and I'm somewhat concerned that this means many other bases don't converge either. I know the error term is approximately a linear dot product from one iteration to the next -- I'm going to try some experiments and I'll report back results later.

Small update: The fixed point, L, for , has L=i, with . I don't know what is special about the fixed point of L=i. I tried literally hundred of random bases between 1.5 and 10, (mostly using a faster version of, which uses a Taylor series for the Schroeder function and its inverse which is 3x faster than the version here). All of the random bases converged, so the problem is isolated. Then I tried bases nearby . Using the default precision (\p 67), I get failures , but not for larger values of delta. Using a higher precision, \p 134, I get failures for , but where the precision plateaus depends on how small delta is. I'll report some graphs later; hopefully I'll start to make some sense of what's going, and why this one particular base may not converge ....
- Sheldon

Messages In This Thread
RE: Precision check on [] fails? - by sheldonison - 06/28/2011, 02:33 PM

Possibly Related Threads...
Thread Author Replies Views Last Post
  Attempt to find a limit point but each step needs doubling the precision... Gottfried 15 32,143 11/09/2014, 10:25 PM
Last Post: tommy1729
  Expansion of base-e pentation andydude 13 38,118 07/02/2011, 01:40 AM
Last Post: Cherrina_Pixie
  How to force precision in SAGE? jaydfox 2 7,682 08/18/2007, 11:08 PM
Last Post: jaydfox

Users browsing this thread: 1 Guest(s)