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Groups > comp.soft-sys.math.mathematica > #1975

Re: MachinePrecision vs. Arbitrary Precision

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Bill Rowe <readnews@sbcglobal.net> writes:

> On 4/27/11 at 5:39 AM, worthless.trash.junk@gmail.com (Rafael Dunn)
> wrote:
>
>>In:=
>>N[Sin[Exp[100]]]
>>N[Sin[Exp[100]], 1]
>>N[Sin[Exp[100]], 11]
>
>>Out:=
>>-0.999105
>>0.1
>>0.14219812366
>
>>I realize that N[exp] = N[exp, MachinePrecision].  This indicates
>>when N[] is asked to calculate to MachinePrecision,
>
> More specifically, this asks hardware to do the required computation.
>
>>it produces an incorrect result in this example.
>
> That is due to the limitations of floating point arithmetic as
> implemented in hardware. The actual result you get will vary
> according to what hardware is being used.

To emphasize that this is the result from hardware here is a program in
the C programming language:

  #include <stdio.h>
  #include <math.h>
  int main(void)
  {
    printf("%g\n", sin(exp(100)));
    return 0;
  }

And here is its output:

  -0.999105

Scott
-- 
Scott Hemphill	hemphill@alumni.caltech.edu
"This isn't flying.  This is falling, with style."  -- Buzz Lightyear

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Re: MachinePrecision vs. Arbitrary Precision Bill Rowe <readnews@sbcglobal.net> - 2011-04-28 10:34 +0000
  Re: MachinePrecision vs. Arbitrary Precision Scott Hemphill <hemphill@hemphills.net> - 2011-04-29 11:30 +0000

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