Groups > comp.lang.java.programmer > #6831

Re: higher precision doubles

From	Jan Burse <janburse@fastmail.fm>
Newsgroups	comp.lang.java.programmer
Subject	Re: higher precision doubles
Date	2011-08-06 23:20 +0200
Organization	albasani.net
Message-ID	<j1kb73$h3p$1@news.albasani.net> (permalink)
References	<j1hqc1$1ch$1@news.albasani.net> <strictfp-20110806003831@ram.dialup.fu-berlin.de> <j1k4db$1n2$1@news.albasani.net> <j1k87t$kol$1@dont-email.me>

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Hi

According to ISO LIA it is desired NOT to print eps or a multiple
of eps as zero. This doesn't bother me at all, it rather shows
the high quality of the Java float writing algorithm.

So if you add x == 0 to your solution, you would get:

 > -0.000000, false
 > -0.000000, false

And BTW the negative sign in front of the zero anyway indicates
that some rounding was going on, and not a true zero was returned
by the computation. And you could try x == 0 || x == -0, if this
is possible, and you would still get false.

Bye

markspace schrieb:
> On 8/6/2011 12:24 PM, Jan Burse wrote:
>> Motivating example, in Go we have:
> ...
>> In Java we have:
> ...
>> zero1=-2.4492935982947064E-16
>> zero2=-2.4492935982947064E-16
>
>
> I honestly don't find this very motivating. Zero is what you make of it.
> In engineering I learning that 6 digits are sufficient for almost any
> practical task. 30 is way overkill.
>
> As far as printing is concerned, don't get confused by the funny
> numbers. It's just a matter of understanding and selecting the correct
> format.
>
> Counter motivating example:
>
> public class FpPrint {
>
> public static void main( String[] args )
> {
> System.out.printf( "%6.6f\n", Math.sin( Math.PI * 2 ) );
> System.out.printf( "%6.6f\n", StrictMath.sin( StrictMath.PI * 2 ) );
> }
> }
>
> run:
> -0.000000
> -0.000000
> BUILD SUCCESSFUL (total time: 0 seconds)
>
>
> Here we understand what significant digits mean, and we print the
> correct and desired number of digits. We're good.
>
> There's many times many accumulated errors between 0 and 2 x 10^-16 .
> Just because the default Java printer doesn't print a "0" doesn't mean
> we should panic. That's really all your demonstrating here: the default
> printing behavior of System.out.println.
>
>

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Thread

higher precision doubles Jan Burse <janburse@fastmail.fm> - 2011-08-06 00:20 +0200
  Re: higher precision doubles Patricia Shanahan <pats@acm.org> - 2011-08-06 03:35 -0700
    Re: higher precision doubles Jan Burse <janburse@fastmail.fm> - 2011-08-06 13:03 +0200
      Re: higher precision doubles BGB <cr88192@hotmail.com> - 2011-08-06 12:20 -0700
        Re: higher precision doubles Jan Burse <janburse@fastmail.fm> - 2011-08-06 23:30 +0200
          Re: higher precision doubles BGB <cr88192@hotmail.com> - 2011-08-06 16:12 -0700
            Re: higher precision doubles Jan Burse <janburse@fastmail.fm> - 2011-08-07 01:35 +0200
              Re: higher precision doubles BGB <cr88192@hotmail.com> - 2011-08-06 19:26 -0700
    Re: higher precision doubles supercalifragilisticexpialadiamaticonormalizeringelimatisticantations <supercalifragilisticexpialadiamaticonormalizeringelimatisticantations@averylongandannoyingdomainname.com> - 2011-08-09 00:42 -0400
      Re: higher precision doubles Patricia Shanahan <pats@acm.org> - 2011-08-09 04:07 -0700
        Re: higher precision doubles Jan Burse <janburse@fastmail.fm> - 2011-08-09 14:00 +0200
          Re: higher precision doubles Patricia Shanahan <pats@acm.org> - 2011-08-09 09:07 -0700
            Re: higher precision doubles Jan Burse <janburse@fastmail.fm> - 2011-08-10 08:50 +0200
        Re: higher precision doubles supercalifragilisticexpialadiamaticonormalizeringelimatisticantations <supercalifragilisticexpialadiamaticonormalizeringelimatisticantations@averylongandannoyingdomainname.com> - 2011-08-10 20:16 -0400
      Re: higher precision doubles Joshua Cranmer <Pidgeot18@verizon.invalid> - 2011-08-09 10:11 -0500
        Re: higher precision doubles Arne Vajhøj <arne@vajhoej.dk> - 2011-08-09 22:40 -0400
          Re: higher precision doubles Joshua Cranmer <Pidgeot18@verizon.invalid> - 2011-08-09 22:06 -0500
            Re: higher precision doubles BGB <cr88192@hotmail.com> - 2011-08-10 08:53 -0700
  Re: higher precision doubles Jan Burse <janburse@fastmail.fm> - 2011-08-06 21:24 +0200
    Re: higher precision doubles markspace <-@.> - 2011-08-06 13:29 -0700
      Re: higher precision doubles Jan Burse <janburse@fastmail.fm> - 2011-08-06 23:20 +0200
        Re: higher precision doubles markspace <-@.> - 2011-08-06 15:43 -0700
          Re: higher precision doubles Jan Burse <janburse@fastmail.fm> - 2011-08-07 01:06 +0200
            Re: higher precision doubles Patricia Shanahan <pats@acm.org> - 2011-08-06 16:21 -0700
              Re: higher precision doubles Jan Burse <janburse@fastmail.fm> - 2011-08-07 01:34 +0200
                Re: higher precision doubles Patricia Shanahan <pats@acm.org> - 2011-08-06 21:32 -0700
                Re: higher precision doubles Jan Burse <janburse@fastmail.fm> - 2011-08-07 17:24 +0200
                Re: higher precision doubles Jan Burse <janburse@fastmail.fm> - 2011-08-07 17:39 +0200
                Re: higher precision doubles Patricia Shanahan <pats@acm.org> - 2011-08-07 09:26 -0700
                Re: higher precision doubles Jan Burse <janburse@fastmail.fm> - 2011-08-07 21:23 +0200
                Re: higher precision doubles Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-08-07 20:48 -0400
                Re: higher precision doubles Jan Burse <janburse@fastmail.fm> - 2011-08-08 09:05 +0200
                Re: higher precision doubles Patricia Shanahan <pats@acm.org> - 2011-08-08 05:37 -0700
                Re: higher precision doubles Jan Burse <janburse@fastmail.fm> - 2011-08-08 19:08 +0200
                Re: higher precision doubles Jan Burse <janburse@fastmail.fm> - 2011-08-08 19:16 +0200
                Re: higher precision doubles Jan Burse <janburse@fastmail.fm> - 2011-08-08 19:29 +0200
                Re: higher precision doubles Joshua Cranmer <Pidgeot18@verizon.invalid> - 2011-08-08 21:34 -0500
                Re: higher precision doubles BGB <cr88192@hotmail.com> - 2011-08-08 13:49 -0700
                Re: higher precision doubles Jan Burse <janburse@fastmail.fm> - 2011-08-09 01:08 +0200
                Re: higher precision doubles BGB <cr88192@hotmail.com> - 2011-08-09 02:44 -0700
                Re: higher precision doubles Jan Burse <janburse@fastmail.fm> - 2011-08-09 12:52 +0200
                Re: higher precision doubles BGB <cr88192@hotmail.com> - 2011-08-09 13:15 -0700
                Re: higher precision doubles BGB <cr88192@hotmail.com> - 2011-08-07 13:51 -0700
              Re: higher precision doubles Jan Burse <janburse@fastmail.fm> - 2011-08-07 01:59 +0200
        Re: higher precision doubles Joshua Cranmer <Pidgeot18@verizon.invalid> - 2011-08-08 21:03 -0500
    Re: higher precision doubles Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-08-06 17:33 -0400
    Re: higher precision doubles Patricia Shanahan <pats@acm.org> - 2011-08-06 14:51 -0700
      Re: higher precision doubles Jan Burse <janburse@fastmail.fm> - 2011-08-07 00:57 +0200

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