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Re: Why Mathematica does not issue a warning when the calculations are losing so much precision that the results are not anymore useful?

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  • Subject: [mg117561] Re: Why Mathematica does not issue a warning when the calculations are losing so much precision that the results are not anymore useful?
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Tue, 22 Mar 2011 05:11:06 -0500 (EST)

Just specify the precision

Table[
  N[FractionalPart[(6 + Sqrt[2])^20], n],
  {n, 1, 20}] // Column

Table[
  N[FractionalPart[(6 + Sqrt[2])^20], n] // InputForm,
  {n, 1, 20}] // Column


Bob Hanlon

---- John Travolta Sardus <pireddag at hotmail.com> wrote: 

=============
With Mathematica 8.0.1

N[FractionalPart[(6 + Sqrt[2])^20]]

Result:

-160.

Is it a problem for all numerical software being able to recognize when 
these calculations cannot be performed with the given machine accuracy? 
Does this happen in this case only (where a wrong result is easily 
recognized) or in other cases too?

Thanks for any answer,

Giovanni



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