Another possible way to accelerate MB set deep zooming

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knighty

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Re: Another possible way to accelerate MB set deep zooming

« Reply #45 on: February 12, 2018, 09:53:04 AM »
The difference is because you are scaling b.

• 3f
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Re: Another possible way to accelerate MB set deep zooming

« Reply #46 on: February 12, 2018, 11:57:05 AM »
The difference is because you are scaling b.
Then, if I understand correctly what you are doing, it becomes $$r=|a_{01}/a_{02}|b_{max}$$ with my a's.
For the example I attached then find r = 1.25e-41 which works, but the s-orbit escapes already almost everywhere in the mini defeating the purpose of the method.
r=6e-20 is the value I find by manual tuning there.

knighty

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Re: Another possible way to accelerate MB set deep zooming

« Reply #47 on: February 12, 2018, 04:27:12 PM »
if |a01/a02| = 7e10 and bmax = 2.3e-41 you get r = 1.6e-30 not 1.25e-41. If you zoom at 6e-30 you'll see that it is the point where the period 111 root appears.
In this location I find that a bailout of 1e-25 works also. The numbers are given for nanomb particular algorithm. It may be different for you.

• 3f
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Re: Another possible way to accelerate MB set deep zooming

« Reply #48 on: February 12, 2018, 07:46:22 PM »
if |a01/a02| = 7e10 and bmax = 2.3e-41 you get r = 1.6e-30 not 1.25e-41. If you zoom at 6e-30 you'll see that it is the point where the period 111 root appears.
In this location I find that a bailout of 1e-25 works also. The numbers are given for nanomb particular algorithm. It may be different for you.
Sorry I made a mistake: |a01/a02| = 0.27 and bmax = 4.6e-41 is what I get for the location. It seems I find the center of one of the bulbs attached to the mini.

If your program does something different from what was discussed so far I can't figure it out from your code, so there is not much to discuss then. Nevertheless, I think we agree r should be as large as possible, does your method really find such a value for every location?

My feeling is the term "escape radius" is a misnomer: we need an error condition with some sound justification to stop the super iteration which may not have the form |z|>r for some constant r, but how??

• 3f
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Re: Another possible way to accelerate MB set deep zooming

« Reply #49 on: February 12, 2018, 11:42:52 PM »
A method I haven't seen fail yet is for the (K,M) polynomial for fp compute 3 more terms (K+1,M+1) and use that as error estimate.
Then "escape" if $$\Delta z > h^2$$ with h pixel radius. I have no idea why h^2 instead of h, just found this experimentally. Maybe it should be h*minbrot size or something like that.
I've tried to break it, but have not succeeded yet. No warranties

knighty

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Re: Another possible way to accelerate MB set deep zooming

« Reply #50 on: February 13, 2018, 11:50:11 AM »
If your program does something different from what was discussed so far I can't figure it out from your code, so there is not much to discuss then.
Nothing fundamentally different. I was pointing to the possible fact that my implementation is different from yours so the numbers could be different. That said, IMHO you need to check your computation of r again.

Nevertheless, I think we agree r should be as large as possible, does your method really find such a value for every location?
Sure! but it is not critical. It is just like what happens with the regular escape radius: 1e20 is attained only one iteration after 1e10.
I believe "my" method should work for every location. I'm assuming that the MB set is not perturbed, we always begin at z=0. The idea is: if one approximates a high degree polynomial P with a low a low degree polynomial Q, Q will approximate well P in the area where they both agree about their roots. This is something that could be proven true (or false) when phrased in a precise manner.

My feeling is the term "escape radius" is a misnomer: we need an error condition with some sound justification to stop the super iteration which may not have the form |z|>r for some constant r, but how??
There is the question.

• 3f
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Re: Another possible way to accelerate MB set deep zooming

« Reply #51 on: February 13, 2018, 05:52:08 PM »
That said, IMHO you need to check your computation of r again.
Can you tell me what value you get for $$a_{01}/a_{02}$$ in a1.kfr (or any other example you like) so I can check?
Edit: Probably found it, I was looking at SA coefficients instead of SSA, really dumb. For a1.kfr I get
r = 3.318071694457150e-30
However this results in s-orbit escaping inside most of the mini.
Largest escape r without problems I find is r=1e-13.
With the "last term error <h^2" method there is no real r but no point in the mini s-escapes.
« Last Edit: February 13, 2018, 07:38:19 PM by gerrit »

• 3f
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Re: Another possible way to accelerate MB set deep zooming

« Reply #52 on: February 14, 2018, 04:24:48 AM »
r = |a01|/|a02|
I think I got my bugs out. Your method works great for me provided you meant $$|z|^2>r$$ is the escape condition.
With $$|z|>r$$ I get regions inside the mini escaping when mini is large in the view.

knighty

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Re: Another possible way to accelerate MB set deep zooming

« Reply #53 on: February 14, 2018, 01:35:41 PM »
Exactly! That is because we do the test when the reference returns to 0. If we do one regular iteration, z is squared then c is added.

• 3f
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Re: Another possible way to accelerate MB set deep zooming

« Reply #54 on: February 14, 2018, 05:48:47 PM »
Exactly! That is because we do the test when the reference returns to 0. If we do one regular iteration, z is squared then c is added.
I don't understand the rationale behind your method, why does it work?
Quote
You mean "truncation error threshold >tol=h^2"?  I found one example where tol is too small, the original warped one we did. No-escape region doesn't cover entire mini (though most). Not surprising as the h^2 was just a guess.

knighty

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Re: Another possible way to accelerate MB set deep zooming

« Reply #55 on: February 15, 2018, 12:34:50 PM »
I don't know why exactly it works so this is just a sketch. It is more a hunch than anything else so I'm not sure about 90% of what follows  :
When approximating a polynomial P with another lower degree polynomial Q (let's say at a simple root of P) at some distance r, the roots of P and Q become different. Therefore, the distance at which Q approximate P well is less than r. If we don't know at which r the roots of P and Q disagree, let's take the smallest r where Q have a root (this is a second root because our approximation is around a root of P) and divide it by some number, say 10, for safety. I guess the higher the degree of Q is the lower the safety divisor number can be...

• 3f
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Re: Another possible way to accelerate MB set deep zooming

« Reply #56 on: February 15, 2018, 11:42:37 PM »
I don't know why exactly it works so this is just a sketch. It is more a hunch than anything else so I'm not sure about 90% of what follows  :
When approximating a polynomial P with another lower degree polynomial Q (let's say at a simple root of P) at some distance r, the roots of P and Q become different. Therefore, the distance at which Q approximate P well is less than r. If we don't know at which r the roots of P and Q disagree, let's take the smallest r where Q have a root (this is a second root because our approximation is around a root of P) and divide it by some number, say 10, for safety. I guess the higher the degree of Q is the lower the safety divisor number can be...
So if period is p all the roots of P are at period p mini's. Then probably $$r<2^{-2p}$$:
https://fractalforums.org/fractal-mathematics-and-new-theories/28/newton-raphson-zooming/481/msg2906#msg2906

That's too small in general though, but I found it's accurate (agree with your r) near -2 for minis on the real axis.

Just a useless comment...

knighty

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Re: Another possible way to accelerate MB set deep zooming

« Reply #57 on: February 19, 2018, 10:55:30 AM »
So if period is p all the roots of P are at period p mini's. Then probably $$r<2^{-2p}$$:
That doesn't happen.

• 3f
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Re: Another possible way to accelerate MB set deep zooming

« Reply #58 on: February 28, 2018, 05:14:38 AM »
Any ideas on glitch correction with the SSA? I tried doing SSA iterations on the first mini, then PT to finish off the escaped ones, collecting all glitches detected as usual. I then find a random glitch, find a period/nucleus in it with usual ball/Newton method, compute new SSA, then process glitches with SSA + PT followup etc. It seems to work but I'm not sure it's the best way to do it.

knighty

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Re: Another possible way to accelerate MB set deep zooming

« Reply #59 on: March 04, 2018, 08:40:17 AM »
The only simple approach I can think of is to do exactly the same thing as with regular SA. Beside that I'm out of ideas.

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