GWT-client math vs. java-math

Hi guys, we are developing a GWT-project with a lot of shared files. We discovered a few discrepancies in the gwt-math and server-math and wanted to share them for anybody else having those issues:

• First and foremost: all native double calculations are identical (+ - * / %)
• All trig-functions (sin,cos,tan,asin,acos,atan,atan2) seem to produces slightly different results. We recommend doing your own impl using lookup-maps
• sqrt,log and pow seem to be identical although we only tested sqrt thoroughly
• As far as we know all functions like max,min,abs etc are identical
• toDegrees and toRadian are actually different because GWT uses a constant for 180./PI and PI/180. which changes the order of operation compared to java
• For serialization of doubles we strongly suggest using Double.doubleToLongbits and Double.longBitsToDouble. You can additionally use Long.toString(long,32) and Long.parseString(string,32) to compress the String-representation
  

I hope we can help some people with this info. Especially the toDegrees/toRadians was very surprising to find. This issue was reported though and might be fixed in a future GWT-version (we tested 2.6.1).

In case you are interested how we solved the issues here is the open-source-part of our project so you can check it out

Regards

Oskar Stangenberg

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