Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.soft-sys.math.mathematica > #3499

Re: Numerical accuracy/precision - this is a bug or a feature?

From Richard Fateman <fateman@cs.berkeley.edu>
Newsgroups comp.soft-sys.math.mathematica
Subject Re: Numerical accuracy/precision - this is a bug or a feature?
Date 2011-07-05 09:15 +0000
Organization Steven M. Christensen and Associates, Inc and MathTensor, Inc.
Message-ID <iuuko3$eqi$1@smc.vnet.net> (permalink)
References <ius5op$2g7$1@smc.vnet.net> <ius7hm$358$1@smc.vnet.net>

Show all headers | View raw

In brief:  yes to both.

On 7/4/2011 4:18 AM, Kevin J. McCann wrote:
...
>>
>> 1. N[2.0,20] should give 2 with accuracy/precision/whatsever about 20
>> decimal digits, i.e. 2.00000000000000000000
>

WRI will defend this as a feature.

You thought that the semantics of N[] were the same as SetPrecision
e.g.

N[SetPrecision[2.0, 20]*N[Sqrt[2], 20], 20]


works as you expected.

So from your perspective, and from the perspective of anyone else who 
thinks along the same lines, it is a bug.  I would prefer to call it
a design error.

2.0  (indeed, any floating point number) is a perfectly respectable way 
of denoting a number that can be expressed in higher precision by adding 
binary zeros. WRI doesn't agree.

RJF

Back to comp.soft-sys.math.mathematica | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Numerical accuracy/precision - this is a bug or a feature? "slawek" <slawek@host.pl> - 2011-07-04 10:47 +0000
  Re: Numerical accuracy/precision - this is a bug or a feature? "Kevin J. McCann" <kjm@KevinMcCann.com> - 2011-07-04 11:14 +0000
    Re: Numerical accuracy/precision - this is a bug or a feature? "slawek" <slawek@host.pl> - 2011-07-05 09:17 +0000
      Re: Numerical accuracy/precision - this is a bug or a feature? "Kevin J. McCann" <Kevin.McCann@umbc.edu> - 2011-07-06 09:35 +0000
        Re: Numerical accuracy/precision - this is a bug or a feature? "slawek" <slawek@host.pl> - 2011-07-07 11:40 +0000
      Re: Numerical accuracy/precision - this is a bug or a feature? Daniel Lichtblau <danl@wolfram.com> - 2011-07-07 11:34 +0000
    Re: Numerical accuracy/precision - this is a bug or a feature? "Oleksandr Rasputinov" <oleksandr_rasputinov@hmamail.com> - 2011-07-06 09:39 +0000
      Re: Numerical accuracy/precision - this is a bug or a feature? Richard Fateman <fateman@cs.berkeley.edu> - 2011-07-07 11:33 +0000
    Re: Numerical accuracy/precision - this is a bug or a feature? Noqsi <noqsiaerospace@gmail.com> - 2011-07-08 08:51 +0000
      Re: Numerical accuracy/precision - this is a bug or a feature? "slawek" <slawek@host.pl> - 2011-07-12 11:01 +0000
    Re: Numerical accuracy/precision - this is a bug or a feature? "Oleksandr Rasputinov" <oleksandr_rasputinov@hmamail.com> - 2011-07-08 09:04 +0000
      Re: Numerical accuracy/precision - this is a bug or a feature? Richard Fateman <fateman@cs.berkeley.edu> - 2011-07-09 11:34 +0000
      Re: Numerical accuracy/precision - this is a bug or a feature? "slawek" <slawek@host.pl> - 2011-07-12 11:02 +0000
    Re: Numerical accuracy/precision - this is a bug or a feature? "Oleksandr Rasputinov" <oleksandr_rasputinov@hmamail.com> - 2011-07-09 11:37 +0000
      Re: Numerical accuracy/precision - this is a bug or a feature? Noqsi <noqsiaerospace@gmail.com> - 2011-07-13 07:11 +0000
        Re: Numerical accuracy/precision - this is a bug or a feature? Richard Fateman <fateman@cs.berkeley.edu> - 2011-07-14 09:23 +0000
        Re: Numerical accuracy/precision - this is a bug or a feature? Andrzej Kozlowski <akoz@mimuw.edu.pl> - 2011-07-15 01:19 +0000
        Re: Numerical accuracy/precision - this is a bug or a feature? "W. Craig Carter" <ccarter@mit.edu> - 2011-07-15 01:25 +0000
        Re: Numerical accuracy/precision - this is a bug or a feature? Andrzej Kozlowski <akoz@mimuw.edu.pl> - 2011-07-15 08:12 +0000
        Re: Numerical accuracy/precision - this is a bug or a feature? Andrzej Kozlowski <akoz@mimuw.edu.pl> - 2011-07-16 09:45 +0000
        Re: Numerical accuracy/precision - this is a bug or a feature? Andrzej Kozlowski <akoz@mimuw.edu.pl> - 2011-07-16 09:40 +0000
    Re: Numerical accuracy/precision - this is a bug or a feature? Noqsi <noqsiaerospace@gmail.com> - 2011-07-13 07:12 +0000
    Re: Numerical accuracy/precision - this is a bug or a feature? Noqsi <noqsiaerospace@gmail.com> - 2011-07-15 01:23 +0000
      Re: Numerical accuracy/precision - this is a bug or a feature? Richard Fateman <fateman@cs.berkeley.edu> - 2011-07-15 08:10 +0000
    Re: Numerical accuracy/precision - this is a bug or a feature? Noqsi <noqsiaerospace@gmail.com> - 2011-07-16 09:41 +0000
      Re: Numerical accuracy/precision - this is a bug or a feature? Richard Fateman <fateman@cs.berkeley.edu> - 2011-07-17 10:02 +0000
        Re: Numerical accuracy/precision - this is a bug or a feature? "slawek" <slawek@host.pl> - 2011-07-18 10:14 +0000
      Re: Numerical accuracy/precision - this is a bug or a feature? Andrzej Kozlowski <akoz@mimuw.edu.pl> - 2011-07-18 10:17 +0000
        Re: Numerical accuracy/precision - this is a bug or a feature? Richard Fateman <fateman@cs.berkeley.edu> - 2011-07-19 10:55 +0000
  Re: Numerical accuracy/precision - this is a bug or a feature? "Kevin J. McCann" <kjm@KevinMcCann.com> - 2011-07-04 11:18 +0000
    Re: Numerical accuracy/precision - this is a bug or a feature? Richard Fateman <fateman@cs.berkeley.edu> - 2011-07-05 09:15 +0000
      Re: Numerical accuracy/precision - this is a bug or a feature? "slawek" <slawek@host.pl> - 2011-07-06 09:34 +0000
      Re: Numerical accuracy/precision - this is a bug or a feature? Daniel Lichtblau <danl@wolfram.com> - 2011-07-07 11:35 +0000
        Re: Numerical accuracy/precision - this is a bug or a feature? Richard Fateman <fateman@cs.berkeley.edu> - 2011-07-08 08:53 +0000

csiph-web