Hi Alan, While all this is find it does not explain the following observation using the same CPU: VS2015 the delta is zero
For all other VS dated back to 2003 the delta is non-zero. In fact my friend has shown me his code that led him to question this: He has a web server implementing that simple expression. When the server was hosted in VS2015 IIS (v10) Express and in a local IIS 7.5, the results are different. One returning perfect zero while the other the delta I have reported. There is hardly any accumulated error. It seems to be MS finally decides that the result should be zero (previously some mistake or simplistic approach) so that it is the same as Java, Swift and C/C++. Something dodgy to me. My friend's web demo is pretty much the same as mine using C/Com and .Net assembly resulting in two different values. For those that are using this for SCIENTIFIC calculations, I urge you to do fine grain test them using Learning Test when moving to and from VS2015 or Roslyn. It seems VS2015 has changed something leading to the observation. Just to make sure the change does not have impact on it. Alternately those developed in VS2015 but run with code developed in earlier compiler one needs to implement floating point defensive code. If you have to do some SCIENTIFIC computation of running that expression or more complex one a few hundred times, the result if not taken care of of the type's accuracy at each iteration, the end result will have accumulation error that puts the end result within the precision of the type. Clearly that is wrong and should not be so sensitive to version change of the VS. In fairness scientific calculation is best to be performed in Double because more floating point operations are performed internally in double. Doing so with produce a number of 5.55E-017 which is the same as produced by Java and C. Rover -- View this message in context: http://mono.1490590.n4.nabble.com/Why-is-0-1f-0-2f-0-3f-produces-such-a-large-error-number-tp4667837p4667862.html Sent from the Mono - General mailing list archive at Nabble.com. _______________________________________________ Mono-list maillist - Mono-list@lists.ximian.com http://lists.ximian.com/mailman/listinfo/mono-list