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Groups > comp.lang.java.programmer > #15872
| Newsgroups | comp.lang.java.programmer |
|---|---|
| From | "Peter J. Holzer" <hjp-usenet2@hjp.at> |
| Subject | Re: (OT) Was: Re: Java processors |
| References | (7 earlier) <jt7kmh$ek3$1@localhost.localdomain> <jt7o6j$tav$1@dont-email.me> <8i6fv7pdnb4riuvnr8a3e7t9htorgsbpm4@4ax.com> <jt9l5c$kdq$1@dont-email.me> <5g2iv7l6d20bufru42qoun737bf80r6kp6@4ax.com> |
| Date | 2012-07-08 12:15 +0200 |
| Message-ID | <slrnjvinei.ugf.hjp-usenet2@hrunkner.hjp.at> (permalink) |
On 2012-07-08 04:19, Gene Wirchenko <genew@ocis.net> wrote:
> On Sat, 07 Jul 2012 11:38:13 -0400, Eric Sosman
><esosman@ieee-dot-org.invalid> wrote:
>> The Wikipedia article on the VSE makes interesting reading. This
>>bit I found somewhat eyebrow-raising:
>>
>> The history of the exchange's index provides a standard case
>> example of large errors arising from seemingly innocuous
>> floating point calculations. [...] The accumulated truncations
>> led to an erroneous loss of around 25 points per month."
>>
>>Not enough RAM to retain the "unimportant" digits?
>
> Probably not. I would blame the use of FP.
Actually, it looks like they used a *fixed point* representation (3
decimal digits), not a floating point representation (although that
doesn't make much difference in this case since the magnitude stays
about the same). The obvious error is that they always truncated the
value, thus accumulating the error[1]. If they had rounded to nearest
most errors would have cancelled out. If they had used double precision
binary floating point numbers and not rounded to 3 decimal digits after
each trade the error would have been too small to notice (about 1 point
in 30 million years).
Anyway, that's a great example. I will use it in the next "binary
floating point is evil" discussion ;-).
hp
[1] The second error was that they tried to compute the new value from
the old value and the change at all - that's pretty much guarantueed
to accumulate some error over time.
--
_ | Peter J. Holzer | Deprecating human carelessness and
|_|_) | Sysadmin WSR | ignorance has no successful track record.
| | | hjp@hjp.at |
__/ | http://www.hjp.at/ | -- Bill Code on asrg@irtf.org
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Java processors bob smith <bob@coolfone.comze.com> - 2012-07-05 08:01 -0700
Re: Java processors Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-07-05 11:28 -0400
Re: Java processors BGB <cr88192@hotmail.com> - 2012-07-05 13:00 -0500
Re: Java processors Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-07-05 14:31 -0400
Re: Java processors BGB <cr88192@hotmail.com> - 2012-07-05 16:42 -0500
Re: Java processors Arne Vajhøj <arne@vajhoej.dk> - 2012-07-05 20:30 -0400
Re: Java processors BGB <cr88192@hotmail.com> - 2012-07-05 21:12 -0500
Re: Java processors Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-07-06 00:13 -0400
Re: Java processors Roedy Green <see_website@mindprod.com.invalid> - 2012-07-06 13:26 -0700
Re: Java processors Gene Wirchenko <genew@ocis.net> - 2012-07-06 13:50 -0700
Re: Java processors Lew <lewbloch@gmail.com> - 2012-07-06 14:17 -0700
Re: Java processors Roedy Green <see_website@mindprod.com.invalid> - 2012-07-06 19:07 -0700
Re: Java processors BGB <cr88192@hotmail.com> - 2012-07-07 09:34 -0500
Re: Java processors Roedy Green <see_website@mindprod.com.invalid> - 2012-07-07 21:01 -0700
Re: Java processors BGB <cr88192@hotmail.com> - 2012-07-08 00:28 -0500
Re: Java processors Lew <noone@lewscanon.com> - 2012-07-07 23:00 -0700
Re: Java processors BGB <cr88192@hotmail.com> - 2012-07-08 10:20 -0500
Re: Java processors Lew <noone@lewscanon.com> - 2012-07-08 09:16 -0700
Re: Java processors Martin Gregorie <martin@address-in-sig.invalid> - 2012-07-08 17:46 +0000
Re: Java processors Lew <noone@lewscanon.com> - 2012-07-08 11:52 -0700
Re: Java processors Martin Gregorie <martin@address-in-sig.invalid> - 2012-07-08 21:41 +0000
Re: Java processors Lew <noone@lewscanon.com> - 2012-07-08 17:56 -0700
Re: Java processors Roedy Green <see_website@mindprod.com.invalid> - 2012-07-08 19:44 -0700
Re: Java processors Lew <noone@lewscanon.com> - 2012-07-09 23:41 -0700
Re: Java processors David Lamb <dalamb@cs.queensu.ca> - 2012-07-16 13:22 -0400
Re: Java processors Lew <lewbloch@gmail.com> - 2012-07-16 14:03 -0700
Re: Java processors Roedy Green <see_website@mindprod.com.invalid> - 2012-07-08 19:42 -0700
Re: Java processors Daniele Futtorovic <da.futt.news@laposte-dot-net.invalid> - 2012-07-10 01:13 +0200
Re: Java processors Lew <lewbloch@gmail.com> - 2012-07-09 16:26 -0700
Re: Java processors Roedy Green <see_website@mindprod.com.invalid> - 2012-07-11 15:41 -0700
Re: Java processors Daniele Futtorovic <da.futt.news@laposte-dot-net.invalid> - 2012-07-12 01:02 +0200
Re: Java processors Wanja Gayk <brixomatic@yahoo.com> - 2012-07-21 18:46 +0200
Re: Java processors Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-07-21 13:05 -0400
Re: Java processors Wanja Gayk <brixomatic@yahoo.com> - 2012-07-21 19:23 +0200
Re: Java processors Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-07-21 14:10 -0400
Re: Java processors Wanja Gayk <brixomatic@yahoo.com> - 2012-07-23 01:17 +0200
Re: Java processors Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-07-22 20:15 -0400
Re: Java processors Daniele Futtorovic <da.futt.news@laposte-dot-net.invalid> - 2012-07-22 15:13 +0200
Re: Java processors Roedy Green <see_website@mindprod.com.invalid> - 2012-07-06 19:03 -0700
Re: Java processors Roedy Green <see_website@mindprod.com.invalid> - 2012-07-08 19:51 -0700
Re: Java processors Roedy Green <see_website@mindprod.com.invalid> - 2012-07-07 21:17 -0700
Re: Java processors Lew <noone@lewscanon.com> - 2012-07-07 23:04 -0700
Re: Java processors Roedy Green <see_website@mindprod.com.invalid> - 2012-07-08 09:29 -0700
Re: Java processors Lew <noone@lewscanon.com> - 2012-07-08 11:57 -0700
Re: Java processors Wanja Gayk <brixomatic@yahoo.com> - 2012-07-08 15:40 +0200
Re: Java processors BGB <cr88192@hotmail.com> - 2012-07-08 10:36 -0500
Re: Java processors Lew <lewbloch@gmail.com> - 2012-07-06 11:31 -0700
Re: Java processors Jim Janney <jjanney@shell.xmission.com> - 2012-07-05 13:02 -0600
Re: Java processors BGB <cr88192@hotmail.com> - 2012-07-05 16:09 -0500
Re: Java processors Jan Burse <janburse@fastmail.fm> - 2012-07-06 01:29 +0200
Re: Java processors Martin Gregorie <martin@address-in-sig.invalid> - 2012-07-06 00:42 +0000
Re: Java processors Roedy Green <see_website@mindprod.com.invalid> - 2012-07-06 13:53 -0700
Re: Java processors Martin Gregorie <martin@address-in-sig.invalid> - 2012-07-06 21:18 +0000
Re: Java processors Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-07-06 18:17 -0400
Re: Java processors Martin Gregorie <martin@address-in-sig.invalid> - 2012-07-06 22:29 +0000
Re: Java processors Roedy Green <see_website@mindprod.com.invalid> - 2012-07-06 19:10 -0700
Re: Java processors BGB <cr88192@hotmail.com> - 2012-07-07 09:42 -0500
Re: Java processors Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-07-07 10:58 -0400
(OT) Was: Re: Java processors Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-07-07 11:38 -0400
Re: (OT) Was: Re: Java processors Gene Wirchenko <genew@ocis.net> - 2012-07-07 21:19 -0700
Re: (OT) Was: Re: Java processors "Peter J. Holzer" <hjp-usenet2@hjp.at> - 2012-07-08 12:15 +0200
Re: Java processors Gene Wirchenko <genew@ocis.net> - 2012-07-07 21:17 -0700
Re: Java processors Jim Janney <jjanney@shell.xmission.com> - 2012-07-05 19:14 -0600
Re: Java processors Roedy Green <see_website@mindprod.com.invalid> - 2012-07-06 13:34 -0700
Re: Java processors Jan Burse <janburse@fastmail.fm> - 2012-07-06 23:04 +0200
Re: Java processors Silvio Bierman <silvio@moc.com> - 2012-07-07 00:13 +0200
Re: Java processors Roedy Green <see_website@mindprod.com.invalid> - 2012-07-06 19:16 -0700
Re: Java processors "Peter J. Holzer" <hjp-usenet2@hjp.at> - 2012-07-08 11:37 +0200
Re: Java processors Roedy Green <see_website@mindprod.com.invalid> - 2012-07-06 13:24 -0700
Re: Java processors BGB <cr88192@hotmail.com> - 2012-07-07 10:06 -0500
Re: Java processors Roedy Green <see_website@mindprod.com.invalid> - 2012-07-06 05:22 -0700
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