On 13 April 2013 09:13, Levente Uzonyi <le...@elte.hu> wrote: > On Sat, 13 Apr 2013, Igor Stasenko wrote: > >> On 12 April 2013 23:47, Norbert Hartl <norb...@hartl.name> wrote: >>> >>> >>> Am 12.04.2013 um 23:23 schrieb Igor Stasenko <siguc...@gmail.com>: >>> >>>> On 12 April 2013 23:14, p...@highoctane.be <p...@highoctane.be> wrote: >>>>> >>>>> +1. No clue either. But discovered the terminate process shortcut to >>>>> kill >>>>> them faster... >>>>> >>>>> Coping over solving ... >>>>> >>>> >>>> One of the "solutions" i proposed is to rewrite the code and get rid >>>> of "nano-second" """"synchronization""" of date and time with system >>>> clock >>>> because >>>> a) there is no real users of it (to my knowledge) >>>> b) you cannot have precision higher than precision of system primitive >>>> we're using, >>>> which is in millisecond range.. >>>> >>> Where do you see a nanosecond synchronization? It is still millisecond >>> clock as far as I can see. Only the instVar is called nanos. >> >> >> Ah, sorry.. i mistaken by some orders of magnitude. ;) >> >> The offending code starts from here: >> >> initializeOffsets >> | durationSinceEpoch secondsSinceMidnight nowSecs | >> LastTick := 0. >> nowSecs := self clock secondsWhenClockTicks. >> LastMilliSeconds := self millisecondClockValue. >> durationSinceEpoch := Duration >> days: SqueakEpoch >> hours: 0 >> minutes: 0 >> seconds: nowSecs. >> DaysSinceEpoch := durationSinceEpoch days. >> secondsSinceMidnight := (durationSinceEpoch - >> (Duration >> days: DaysSinceEpoch >> hours: 0 >> minutes: 0 >> seconds: 0)) asSeconds. >> MilliSecondOffset := secondsSinceMidnight * 1000 - >> LastMilliSeconds >> >> (notice that 1000 multiplier, which gives us "nanosecond" precision) >> >> But that's fine.. now look at >> >> secondsWhenClockTicks >> >> "waits for the moment when a new second begins" >> >> | lastSecond | >> >> lastSecond := self primSecondsClock. >> [ lastSecond = self primSecondsClock ] whileTrue: [ (Delay >> forMilliseconds: 1) wait ]. >> >> ^ lastSecond + 1 >> >> that is complete nonsense. Sorry. >> >> This code relying on primSecondsClock resolution, which is..... (drum >> roll..... ) >> 1 second.. > > >> >> then it is combined with millisecondClockValue , as you see later to get >> system time with millisecond precision.. >> >> I am not genius in math and physics.. but even i understand that if >> you measurement has error X >> you cannot get more precision than X, even if you combine it with >> another measurement with higher precision. >> >> (But i can be wrong with that.. if so, please explain why) > > > (1 to: 10) collect: [ :e | > Time secondsWhenClockTicks. [ Time secondsWhenClockTicks ] timeToRun > ]. "==> #(1000 1000 1000 1000 1000 1000 1000 1000 1000 1000)" > > It seems like the resolution is 1 seconds, but the accuracy is 1 millisecond > or smaller. Which means that the code will give you a millisecond resolution > timestamp. >
Both #timeToRun and secondsWhenClockTicks (via Delay) using same primitive - #millisecondClockValue. Sure thing, precision of this primitive should be it is 1 millisecond or smaller.. But it has nothing to do with precision of primSecondsClock and you cannot increase precision of it using #millisecondClockValue. Because this code: [ lastSecond = self primSecondsClock ] whileTrue: [ (Delay forMilliseconds: 1) wait ]. actually means: [ lastSecond = self primSecondsClock ] whileTrue: [ block not less than 1 ms ]. but not: [ lastSecond = self primSecondsClock ] whileTrue: [ block exactly 1 ms ]. the upper bound of "(Delay forMilliseconds: 1) wait" is undefined.. and you know it well. > > About DateAndTime: having it nanosecond resolution is a future proof idea. > It will take a while till software can create better accuracy timestamps. > Reducing the resolution to milliseconds is a very bad idea. The VM and > external software can give you a microsecond or smaller resolution timestamp > which you want to represent as DateAndTime (or whatever class you use to > create a timestamp) in the image. > > Yes i know. My problem is the amount of code which does something "userful" with nanoseconds while everybody knows that we have no such resolution.. and won't have in 10 years or so. > Levente -- Best regards, Igor Stasenko.
