On 16 April 2013 11:32, Henrik Johansen <
henrik.s.johansen@veloxit.no> wrote:
>
> On Apr 15, 2013, at 4:50 PM, Igor Stasenko wrote:
>
>> On 15 April 2013 16:43, Igor Stasenko <
siguctua@gmail.com> wrote:
>>> On 15 April 2013 16:32, Henrik Johansen <
henrik.s.johansen@veloxit.no> wrote:
>>>>
>>>> On Apr 15, 2013, at 3:25 PM, Igor Stasenko wrote:
>>>>
>>>>> On 15 April 2013 12:14, Henrik Johansen <
henrik.s.johansen@veloxit.no> wrote:
>>>>>>
>>>>>> On Apr 13, 2013, at 12:16 AM, Igor Stasenko wrote:
>>>>>>
>>>>>>>
>>>>>>> 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)
>>>>>>
>>>>>> Because, as Levente said in code, resolution �!= accuracy.
>>>>>> When you measure a single sample, sure, that value has an error of max resolution / 2.
>>>>>> But when you measure when that value _changes_, you have an error of the underlying accuracy / 2.
>>>>>> Clock s value: � � � � � � � � �1 � � � � � � � 2
>>>>>> resolution: � � � � � � � � � � |_______|_______|
>>>>>> accuracy: � � � � � � � � � � � |||||||||||||||||||||||||||||||||||
>>>>>> � � � � � � � � � � � � � � � � � � � � � � � � � � � �^
>>>>>> Here's to hoping the above ascii art(?) worked!
>>>>>>
>>>>>> So no, that method is not complete nonsense.
>>>>>>
>>>>> Okay.
>>>>> Now i rewriting the code which uses new primitive (primUTCMicrosecondClock),
>>>>> and then we will no longer need this startup logic nor wrap around
>>>>> check & other gory details...
>>>>> just use a primitive.
>>>>
>>>> Sounds clearer, yes.
>>>>
>>>> However, be aware, at least on my VM:
>>>> [Time millisecondClockValue] bench '34,600,000 per second.'
>>>> [Time primUTCMicrosecondClock] bench '12,400,000 per second.'
>>>>
>>>> Which in my case translated to that in a Time2 class with #now defined:
>>>> now
>>>>
>>>> � � � �| microSecondsToday |
>>>> � � � �microSecondsToday := self primUTCMicrosecondClock \\ 86400000000.
>>>> � � � �^ self seconds: microSecondsToday // 1000000 nanoSeconds: microSecondsToday * 1000
>>>>
>>>> and changing the relatively low-hanging fruit in standard Time (removing Duration creation and other crap):
>>>>
>>>> seconds: seconds nanoSeconds: nanoCount
>>>> � � � �"Answer a Time from midnight."
>>>>
>>>> � � � �^ self basicNew
>>>> � � � � � � � �seconds: seconds nanoSeconds: nanoCount
>>>>
>>>> To benchmarks that looked like this:
>>>> "Old code"
>>>> [Time now ] bench '7,330,000 per second.' '7,280,000 per second.' '7,170,000 per second.'
>>>> "Using microsecondClock every call"
>>>> [Time2 now ] bench �'2,280,000 per second.''2,300,000 per second.' '2,180,000 per second.'
>>>>
>>>> Also note, Time2 lacked translation to Local time, which would be needed for consistency with Time now.
>>>>
>>>
>>> Well, i am not started modifying Time now, (will start in couple minutes ;)
>>> but here results of DateAndTime now
>>> before and after:
>>>
>>> before:
>>>
>>>
>>> [ DateAndTime now ] bench '316,000 per second.'
>>>
>>> after:
>>>
>>> [ DateAndTime now ] bench '414,000 per second.'
>>>
>>>
>>> with Time now, i think even if it will be "2,300,000" answers per second,
>>> it is fairly acceptable , when accuracy of primitive is 1 microsecond,
>>> you actually don't need more than 1 million answers per second, or you
>>> will receive same answers.
>>>
>>> But aside of it, may i ask, why performance is so important/critical
>>> for those? What is use case?
>>>
>>
>> everything is good in comparison:
>>
>> [ self yourself ] bench '58,800,000 per second.'
>>
>> does nothing and just 25 times faster.. than Time now,
>> so what is the point? :)
>
> The point was raising awareness that performance differences are also worthy of measuring when doing a reimplementation, not just code cleanliness.
> A 3x decrease in performance is worth at least consideration as part of a reimplementation, even when the conclusion is "it's plenty fast enough for most uses anyways".
>
> Not to mention, "Made X Y% faster" looks better in the release notes than "Restructured the internals of X" :)
>