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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. >> >>>> >> >>>> >> >>>> >> >>>> _______________________________________________ >> >>>> netcdf-java mailing list >> >>>> netcdf-java@xxxxxxxxxxxxxxxx >> >>>> For list information or to unsubscribe, visit: >> >>>> http://www.unidata.ucar.edu/mailing_lists/ >> >>> >> >>> >> >> >> > >> > >> > _______________________________________________ >> > netcdf-java mailing list >> > netcdf-java@xxxxxxxxxxxxxxxx >> > For list information or to unsubscribe, visit: >> > http://www.unidata.ucar.edu/mailing_lists/ >> > > > _______________________________________________ > netcdf-java mailing list > netcdf-java@xxxxxxxxxxxxxxxx > For list information or to unsubscribe, visit: > http://www.unidata.ucar.edu/mailing_lists/ >
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