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Re: MachinePrecision vs. Arbitrary Precision

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  Re: MachinePrecision vs. Arbitrary Precision Bill Rowe <readnews@sbcglobal.net> - 2011-04-29 11:34 +0000

#1994 — Re: MachinePrecision vs. Arbitrary Precision

On 4/28/11 at 6:33 AM, mukasa@gmail.com (Sseziwa Mukasa) wrote:

>On Apr 27, 2011, at 5:39 AM, Rafael Dunn wrote:

>lthe behavior of N[e] and N[e,p] is different even if p
>= MachinePrecision,

Not correct as easily demonstrated by:

In[1]:=
a = RealDigits[N[Pi]];
p = MachinePrecision;
b = RealDigits[N[Pi, p]];
a === b

Out[4]= True

But note if you use $MachinePrecision instead of
MachinePrecision, then you do get a different behavior, i.e.

In[5]:= a = N[Pi, MachinePrecision]

Out[5]= 3.14159

In[6]:= b = N[Pi, $MachinePrecision]

Out[6]= 3.141592653589793

But what is being retained is still identical in both cases.

In[7]:= a === b

Out[7]= True

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