Where is the benefit though? There was a time with 8 bit and 16 bit CPU's floating point should be ignored wherever possible but now it's pretty hard to even find a 32 bit PC. Everything is 64 bit So with current architecture, there is no benefit in worrying about this at all.
Rod Webster *1300 896 832* +61 435 765 611 Vehicle Modifications Network www.vehiclemods.net.au On Sun, 4 Jul 2021 at 19:45, n...@nksb.eu <n...@nksb.eu> wrote: > > Drift might be a problem but due to many significant digits almost > certainly more of an annoyance than a real problem. > > There is however a fundamental difference between ordinary integers or > intepreted as a fixed decimal point and ordinay floating point numbers. For > fixed point some of the lower digits are treated as decimal points though I > never have seen it the other direction will of course also work, for > addition/subtraction there will be no drift. For floating point a number of > bits are used for the number while the others except one bit I think is > used for sign is used to place decimal point. Floating point may store a > very large range of numbers so are usually simpler to use, resolution is > higher around zero, in particular some integer values are missing for large > enough numbers as number of significant numbers are constant. > > Do not think you have any reason to care about drift of absolute value or > square root except then you compare numbers as they usually do not make a > perfect fit. Ideally sqrt(x^2)=x but then using floating point there is a > small difference, or you do nuclear fission and count part of an atom? > > > Den Lördag, Juli 03, 2021 09:32 CEST, skrev Alec Ari via Emc-developers < > emc-developers@lists.sourceforge.net>: > Hello, > > Just curious, how would LinuxCNC detect a lack of precision in floating > point? There are trivial x86_64 specific math instructions which would > probably be faster than what LinuxCNC has used since the beginning but if > these instructions happened to be off by a few decimals somewhere, how > would you know? Would LinuxCNC throw a fault or would the machine just > drift further and further away from where it's supposed to be or what? > > The functions in question are: > > https://git.musl-libc.org/cgit/musl/tree/src/math/x86_64/fabs.c > > and > > https://git.musl-libc.org/cgit/musl/tree/src/math/x86_64/sqrt.c > > Thanks! > > Alec > > > _______________________________________________ > Emc-developers mailing list > Emc-developers@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-developers > > > > > _______________________________________________ > Emc-developers mailing list > Emc-developers@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-developers > _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
