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MathGroup Archive 2005

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FW: precisions

  • To: mathgroup at smc.vnet.net
  • Subject: [mg56002] FW: [mg55973] precisions
  • From: "Tun Myint Aung" <TMA at nus.edu.sg>
  • Date: Wed, 13 Apr 2005 01:10:38 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

 
Dear Mathgroup,

	 I made a mistake in the program. Now it is fine. Thank so much
for your response.

With Regards,

Tun Myint Aung


-----Original Message-----
From: Daniel Lichtblau [mailto:danl at wolfram.com] 
To: mathgroup at smc.vnet.net
Subject: [mg56002] Re: [mg55973] precisions

Tun Myint Aung wrote:
> Hi All,
> 
>     I am doing a calculation involving eigenvalues and eigenvectors 
> for structural mechanics. I encountered with difficulties in numerical

> calculation which is very sensitive to precisions of numerical
numbers.
> I used "SetPrecision[inputdata,100] for my input data. But after I got

> eigenvalues and eigenvectors, these numbers are "MachinePrecision". I 
> tried to change the precision in "Eigenvalues", but there are no 
> options for that. How can I set the precision for the whole notebook?
> 
> 
> With Regards,
> Tun Myint Aung (Graduate Student)
> Civil Engineering Department
> National University of Singapore
> E1A 02-18
> E-mail: g0202015 at nus.edu.sg (or) tma at nus.edu.sg

If the input had machine numbers then SetPrecision[inputdata,100] will
simply fill out with binary zeros. This may or may not be what you want.

As for the result being machine numbers, this almost certainly is an
indication that there was a machine number somewhere in the computation
flow, that is, a number that was not coerced to a bignum of 100 digits.


Daniel Lichtblau
Wolfram Research


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