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Re: Re: Optimizing fixed point iteration

  • To: mathgroup at smc.vnet.net
  • Subject: [mg83135] Re: [mg83100] Re: Optimizing fixed point iteration
  • From: Murray Eisenberg <murray at math.umass.edu>
  • Date: Mon, 12 Nov 2007 05:17:44 -0500 (EST)
  • Organization: Mathematics & Statistics, Univ. of Mass./Amherst
  • References: <200711091017.FAA12104@smc.vnet.net><fh3rmu$13o$1@smc.vnet.net> <200711110754.CAA04395@smc.vnet.net>
  • Reply-to: murray at math.umass.edu

You still didn't say what value of the variable depth you want to use. 
Please look at your code's first line:

   depth;step=.02

Something's missing there.  It should be depth=(some value).  WHAT value?

Yaroslav Bulatov wrote:
> Sorry, only checked code with a non-fresh kernel, it should be
> depth; to terminate in reasonable time, although greater depth
> would give more detail
> 
> On Nov 10, 12:55 am, Murray Eisenberg <mur... at math.umass.edu> wrote:
>> What value of depth are you trying to use??
>>
>> Yaroslav Bulatov wrote:
>>> Can anyone see the trick to speed up the following code significantly?
>>> depth;step=.02;
>>> Table[(c = 0;
>>>    NestWhile[-4 (# - a) (# - b) &, .51, (c++; Abs[#1 - #2] > .1) &, 2,
>>>      depth]; c), {a, -1., 0., step}, {b, 0., 1., step}] // ArrayPlot
>>> This makes a plot of the number of iterations needed for the quadratic
>>> fixed point iterations to converge, as a function of quadratic
>>> parameters, however it's too slow to get sufficient granularity
>> --
>> Murray Eisenberg                     mur... at math.umass.edu
>> Mathematics & Statistics Dept.
>> Lederle Graduate Research Tower      phone 413 549-1020 (H)
>> University of Massachusetts                413 545-2859 (W)
>> 710 North Pleasant Street            fax   413 545-1801
>> Amherst, MA 01003-9305
> 
> 
> 

-- 
Murray Eisenberg                     murray at math.umass.edu
Mathematics & Statistics Dept.
Lederle Graduate Research Tower      phone 413 549-1020 (H)
University of Massachusetts                413 545-2859 (W)
710 North Pleasant Street            fax   413 545-1801
Amherst, MA 01003-9305


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