Hi David, Miklos, thanks a lot for your help. Sorry for this late answer ---I broke my arm the day I put this message on the list and wasn"t to concerned with TinyOS then. I will try out what you proposed and will let you know the results as soon as I'm back to work (likely next Monday).
Regards, Andreas > Hi David, > > On Tue, Feb 9, 2010 at 1:41 AM, David Gay <[email protected]> wrote: > >> On Mon, Feb 8, 2010 at 11:35 AM, Miklos Maroti <[email protected]> >> wrote: >> >>> Janos, Andreas and David, >>> >>> From scale.h the scale32(x,a,b) call calculates x*a/b with fixed point >>> arithmetic without overflow. The offset was added to help rounding, >>> but it was not implemented correctly. If you want to calculate x/b, >>> then it makes sense to calculate it as (x + b>>1)/b to get the >>> rounding effect. However, this is NOT needed here since a/b should be >>> close to 1 and in fact the added offset should be a/(2*b). So I think >>> this is clearly a bug and should be removed! >>> >>> Andras, can you please change the code to >>> >>> async command uint32_t Atm128Calibrate.calibrateMicro(uint32_t n) { >>> return scale32(n, cycles, MAGIC); >>> } >>> >>> async command uint32_t Atm128Calibrate.actualMicro(uint32_t n) { >>> return scale32(n, MAGIC, cycles); >>> } >>> >>> and rerun your experiments? David, can you confirm that this is indeed a >>> bug? >>> >> Yes, your summary is correct (except that the ideal offset would be >> b/2a, which would be ~1/2). >> It might be worth forcing the result to be at least 1 as well - do we >> want calibrateMicro(1)/actualMicro(1) to sometimes give 0? >> > > Yes, you are right. Attached is a code that calculates ROUND(x*a/b), > and I think we should use this instead of FLOOR(x*a/b). We should > change this after the next release. > > I do not think we should care if something becomes 0, since the Alarms > take care of that, or people can check it manually, especially then > the input must be close to 0 too. > > Andreas, did you manage to run some tests? > > Miklos > _______________________________________________ Tinyos-help mailing list [email protected] https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
