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MathGroup Archive 1992

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Would you post this Mathematica question to news group for me, please?

  • To: <MathGroup at yoda.physics.unc.edu>
  • Subject: Would you post this Mathematica question to news group for me, please?
  • From: andrew at ll.mit.edu (Andrew Hecht)
  • Date: Mon, 29 Jun 92 02:35:54 -0400

I have a problem with mathematica, version 2.0 (on NeXT): When I
perform the following iteration using numbers with high precision, I
get erroneous results.  For example, with

	a =
3.750000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000

and

	t = a/2

and using the following iteration technique:

	x = t; Do[Print[x]; x = a x - x^2 ,{140}] ; N[x,80]

the results for the 135th through 140th iteration are

 	3.0, 2.0, 0.0, 0.0
 
 I get the same result when the following technique is used: 
 	NestList[f, t , 140] , 
 where f is the following:
 
 	f[x_] =  a x - x^2
	
Has any one out there encountered a similar problem or know of a
solution?
andrew hecht
andrew at ll.mit.edu





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