On 5 July 2012 18:12, Jon Elson <el...@pico-systems.com> wrote: >> I agree with your disagreement. The problem you describe is likely to >> particularly acute in cases where someone has a 1:3 pulley ratio and >> only bothers to type in the scale factor to as many significant >> figures as they feel necessary. >> >> > Nope, doesn't really make any difference. There are numbers that can be > exactly > represented in floating point. These are combinations of power of two > fractions, > such as 1/2, 1/4, 1/8, etc. But, there are many more values that have > no EXACT > representation, such a the 1/3 you mention. This is not a great problem for > a one-time computation, the error is quite small, depending on the > number of mantissa > bits in that FP format. BUT, there will be error EVERY TIME the computation > is performed.
Perhaps I wasn't clear enough in saying that I now realise that computing a new floating-point delta every time is a stupid idea. I was talking about a different issue, that a million turns * 0.333333 will have a huge error even if it looks like typing the ratio to 6 decimal places in the HAL file looks like it ought to be OK, and probably would be for a typical linear axis. -- atp If you can't fix it, you don't own it. http://www.ifixit.com/Manifesto ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
