Guava provides a good method for this:
http://docs.guava-libraries.googlecode.com/git/javadoc/com/google/common/math/DoubleMath.html#fuzzyEquals%28double,%20double,%20double%29
On Tue, Apr 21, 2015 at 9:33 AM, John Caron <caron@xxxxxxxx> wrote:
> 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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>> >>>> http://www.unidata.ucar.edu/mailing_lists/
>> >>>
>> >>>
>> >>
>> >
>> >
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