#10164: Few digits of precision in N().
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Reporter: gerbicz | Owner: jason
Type: defect | Status:
needs_review
Priority: major | Milestone:
sage-5.1
Component: misc | Resolution:
Keywords: N, digits, numerical approximation | Work issues:
Report Upstream: N/A | Reviewers:
Karl-Dieter Crisman, Benjamin Jones
Authors: Robert Gerbicz, Douglas McNeil | Merged in:
Dependencies: | Stopgaps:
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Old description:
> For {{{ N(1+10**-400000,digits=400001)}}} the displayed number of digits
> is only 400000, it is printing 1. followed by 399999 zeroes. The reason
> is that in functional.py: {{{ prec = int((digits+1) * 3.32192) + 1}}}.
> However {{{log(10)/log(2)~3.3219280948874>3.32192}}}, so if digits is
> large the used precision will be smaller by some digits than the
> requested number of digits.
>
> The suggestion is to use 3.32193 instead of 3.32192, see the trivial
> patch.
New description:
For {{{ N(1+10**-400000,digits=400001)}}} the displayed number of digits
is only 400000, it is printing 1. followed by 399999 zeroes. The reason is
that in functional.py: {{{ prec = int((digits+1) * 3.32192) + 1}}}.
However {{{log(10)/log(2)~3.3219280948874>3.32192}}}, so if digits is
large the used precision will be smaller by some digits than the requested
number of digits.
The suggestion is to use 3.32193 instead of 3.32192, see the trivial
patch.
----
Apply: [attachment:trac_10164_folder_sans_whitespace.patch] to Sage
library
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Comment (by benjaminfjones):
Patchbot: apply only [attachment:trac_10164_folder_sans_whitespace.patch]
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/10164#comment:24>
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