No, that is exact. More like ucar.nc2.Misc
public static boolean closeEnough(float v1, float v2, float maxRelDiff)
{
if(Float.isNaN(v1) && Float.isNaN(v2)) return true;
if(Float.isNaN(v1) || Float.isNaN(v2)) return false; // prob not needed
float diff = Math.abs(v1 - v2);
float largest = Math.max(Math.abs(v1), Math.abs(v2));
return diff <= largest * maxRelDiff;
}
see:
http://www.cygnus-software.com/papers/comparingfloats/comparingfloats.htm
http://floating-point-gui.de/errors/comparison/
On Tue, Apr 21, 2015 at 9:22 AM, Antonio Rodriges <antonio.rrz@xxxxxxxxx>
wrote:
> Like
> Float.compare(a. b) and
> Double.compare(a, b)
>
> 2015-04-21 17:14 GMT+03:00 John Caron <caron@xxxxxxxx>:
> > ok, and you always have to compare floats with a tolerance, not exact.
> ive
> > been bitten many times by that.
> >
> > John
> >
> > On Tue, Apr 21, 2015 at 8:02 AM, Daniele Romagnoli
> > <daniele.romagnoli@xxxxxxxxxxxxxxxx> wrote:
> >>
> >> Hi John,
> >> thanks for your reply.
> >>
> >> The problem I have with this is that I'm setting up a predefined set of
> >> custom CoordinateReferenceSystem definitions:
> >> as an instance, a LambertConformal projection where standard parallels
> is
> >> 25.
> >> Then, I'm parsing the gridMapping attributes in order to try to
> recognize
> >> a known custom CRS and I'm getting no matches since it is expecting 25
> >> instead of 25.00002. (CRS matching checks use WKT parsing).
> >>
> >> In the meantime, I will investigate more on this.
> >> Cheers,
> >> Daniele
> >>
> >>
> >>
> >> ==
> >> GeoServer Professional Services from the experts! Visit
> >> http://goo.gl/NWWaa2 for more information.
> >> ==
> >>
> >> Ing. Daniele Romagnoli
> >> Senior Software Engineer
> >>
> >> GeoSolutions S.A.S.
> >> Via Poggio alle Viti 1187
> >> 55054 Massarosa (LU)
> >> Italy
> >> phone: +39 0584 962313
> >> fax: +39 0584 1660272
> >>
> >> http://www.geo-solutions.it
> >> http://twitter.com/geosolutions_it
> >>
> >> -------------------------------------------------------
> >>
> >> AVVERTENZE AI SENSI DEL D.Lgs. 196/2003
> >>
> >> Le informazioni contenute in questo messaggio di posta elettronica e/o
> >> nel/i file/s allegato/i sono da considerarsi strettamente riservate. Il
> loro
> >> utilizzo è consentito esclusivamente al destinatario del messaggio, per
> le
> >> finalità indicate nel messaggio stesso. Qualora riceviate questo
> messaggio
> >> senza esserne il destinatario, Vi preghiamo cortesemente di darcene
> notizia
> >> via e-mail e di procedere alla distruzione del messaggio stesso,
> >> cancellandolo dal Vostro sistema. Conservare il messaggio stesso,
> divulgarlo
> >> anche in parte, distribuirlo ad altri soggetti, copiarlo, od
> utilizzarlo per
> >> finalità diverse, costituisce comportamento contrario ai principi
> dettati
> >> dal D.Lgs. 196/2003.
> >>
> >>
> >>
> >> The information in this message and/or attachments, is intended solely
> for
> >> the attention and use of the named addressee(s) and may be confidential
> or
> >> proprietary in nature or covered by the provisions of privacy act
> >> (Legislative Decree June, 30 2003, no.196 - Italy's New Data Protection
> >> Code).Any use not in accord with its purpose, any disclosure,
> reproduction,
> >> copying, distribution, or either dissemination, either whole or
> partial, is
> >> strictly forbidden except previous formal approval of the named
> >> addressee(s). If you are not the intended recipient, please contact
> >> immediately the sender by telephone, fax or e-mail and delete the
> >> information in this message that has been received in error. The sender
> does
> >> not give any warranty or accept liability as the content, accuracy or
> >> completeness of sent messages and accepts no responsibility for changes
> >> made after they were sent or for other risks which arise as a result of
> >> e-mail transmission, viruses, etc.
> >>
> >>
> >>
> >> On Tue, Apr 21, 2015 at 2:15 AM, John Caron <caron@xxxxxxxx> wrote:
> >>>
> >>> Hi Daniele:
> >>>
> >>> GRIB projection info is stored in the GRIB file in (at most) 3 bytes,
> so
> >>> has a maximum precision of 24 bits.
> >>>
> >>> Im surprised that you are seeing a problem, it seems unlikely that a
> >>> roundoff in the low order bit of a float should matter.
> >>>
> >>> But theres not really a good reason that we couldnt use doubles if
> >>> needed.
> >>>
> >>> John
> >>>
> >>>
> >>> On Mon, Apr 20, 2015 at 3:45 AM, Daniele Romagnoli
> >>> <daniele.romagnoli@xxxxxxxxxxxxxxxx> wrote:
> >>>>
> >>>> Hi List,
> >>>> I'm using NetCDF Java 4.5.5.
> >>>> I have noticed that when computing the LambertConformal projection
> >>>> components (such as latin1, latin2...) in Grib1Gds I'm getting:
> >>>>
> >>>> latin1 = 25.00001
> >>>> latin2 = 25.05002
> >>>> dx1 = 13.545001
> >>>> dy1 = 13.545001
> >>>>
> >>>> Instead of:
> >>>> latin1 = 25
> >>>> latin2 = 25.05
> >>>> dx1 = 13.545
> >>>> dy1 = 13.545
> >>>>
> >>>> Plus, I'm getting some additional precision loss when extracting these
> >>>> attributes
> >>>> from the associated grid_mapping variable, as numbers (double values).
> >>>> I will surely investigate more on the topic to become more confident
> >>>> with that code and I will read again about representation errors on
> floating
> >>>> point arithmetics so my question could sounds trivial: Why these
> variables
> >>>> and scale constants are floats instead of doubles? (is it for size and
> >>>> performance issues?)
> >>>>
> >>>> Regards,
> >>>> Daniele
> >>>>
> >>>>
> >>>>
> >>>>
> >>>> ==
> >>>> GeoServer Professional Services from the experts! Visit
> >>>> http://goo.gl/NWWaa2 for more information.
> >>>> ==
> >>>>
> >>>> Ing. Daniele Romagnoli
> >>>> Senior Software Engineer
> >>>>
> >>>> GeoSolutions S.A.S.
> >>>> Via Poggio alle Viti 1187
> >>>> 55054 Massarosa (LU)
> >>>> Italy
> >>>> phone: +39 0584 962313
> >>>> fax: +39 0584 1660272
> >>>>
> >>>> http://www.geo-solutions.it
> >>>> http://twitter.com/geosolutions_it
> >>>>
> >>>> -------------------------------------------------------
> >>>>
> >>>> AVVERTENZE AI SENSI DEL D.Lgs. 196/2003
> >>>>
> >>>> Le informazioni contenute in questo messaggio di posta elettronica e/o
> >>>> nel/i file/s allegato/i sono da considerarsi strettamente riservate.
> Il loro
> >>>> utilizzo è consentito esclusivamente al destinatario del messaggio,
> per le
> >>>> finalità indicate nel messaggio stesso. Qualora riceviate questo
> messaggio
> >>>> senza esserne il destinatario, Vi preghiamo cortesemente di darcene
> notizia
> >>>> via e-mail e di procedere alla distruzione del messaggio stesso,
> >>>> cancellandolo dal Vostro sistema. Conservare il messaggio stesso,
> divulgarlo
> >>>> anche in parte, distribuirlo ad altri soggetti, copiarlo, od
> utilizzarlo per
> >>>> finalità diverse, costituisce comportamento contrario ai principi
> dettati
> >>>> dal D.Lgs. 196/2003.
> >>>>
> >>>>
> >>>>
> >>>> The information in this message and/or attachments, is intended solely
> >>>> for the attention and use of the named addressee(s) and may be
> confidential
> >>>> or proprietary in nature or covered by the provisions of privacy act
> >>>> (Legislative Decree June, 30 2003, no.196 - Italy's New Data
> Protection
> >>>> Code).Any use not in accord with its purpose, any disclosure,
> reproduction,
> >>>> copying, distribution, or either dissemination, either whole or
> partial, is
> >>>> strictly forbidden except previous formal approval of the named
> >>>> addressee(s). If you are not the intended recipient, please contact
> >>>> immediately the sender by telephone, fax or e-mail and delete the
> >>>> information in this message that has been received in error. The
> sender does
> >>>> not give any warranty or accept liability as the content, accuracy or
> >>>> completeness of sent messages and accepts no responsibility for
> changes
> >>>> made after they were sent or for other risks which arise as a result
> of
> >>>> e-mail transmission, viruses, etc.
> >>>>
> >>>>
> >>>>
> >>>> _______________________________________________
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> >>>> netcdf-java@xxxxxxxxxxxxxxxx
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> >>>> http://www.unidata.ucar.edu/mailing_lists/
> >>>
> >>>
> >>
> >
> >
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