Re: reads which modify data

right, this solves the "what was the seed" question but we still
suffer performace decrease and exactness..

i've found a solution like this:

game will be created with a random with some seed. when a random event
occurs within a read, it will get next random value from game's random
source. then a dummy transaction will be created which will read
entity's property. during recovery this will create same random
sequence since:

* for some other reason, each read and write are syncronized on game
* game and prevayler's clock is paused at the beginning of each read and write
* prevayler guarantees transaction ordering

so during recovery we will get same sequence of modifying reads with
same transaction (hence random number) sequence

a bit complicated but only solution i have found since now

regards,
r a f t

On Mon, Mar 2, 2009 at 9:35 PM, Klaus Wuestefeld
<[email protected]> wrote:
> The solution described by Edward of having a tick is good. Only the
> ticks will update state, not the queries.
>
> You dont need to have one transaction per tick. You execute them
> lazily, right before every query or transaction:
>
>   synchronized (system) {
>      if ( ! areAllTicksProcessedTill(time))
>         processAllTicksTill(time)
>   }
>
>
>
>> we cannot depend on any pre-seeded sequence
>> since this is a read and there is no guarantee it will occur again in
>> same order.
>
> With the ticks solution you can guarantee there will be exactly one
> tick per logical millisecond and exactly the same number of random
> values will be consumed every time you rerun the same simulation with
> the same transactions.
>
> You just have to make sure Prevayler's clock and your simulation clock
> are consistent.
>
> That is pretty easy since you can configure the clock that Prevayler uses. :)
>
> See you, Klaus.
>
>
> On Mon, Mar 2, 2009 at 10:12 AM, Edward Kimber <[email protected]> wrote:
>> This sounds like some sort of simulation...
>> I would think about having a system clock that triggers a model
>> update/recalculation on every tick.  This system can include your
>> seeded pseudo-random elements and also be deterministic.  You can then
>> allow very fast direct access reads and you don't need to worry about
>> the write operation because all model updates will be performed by the
>> 'tick' transaction.
>> Just an idea. :)
>> Ed
>>
>> 2009/3/2 hakan eryargi <[email protected]>:
>>> ok, this is what i do without the (pseudo)random part: "lazy evaluation"
>>>
>>> for the random part, the problem is how to find a random seed that we
>>> can later find again and use. using same seed is a solution but of
>>> course we dont want that. we are in the middle of a read operation
>>> came from some client at some -truly- random time. so we cant use
>>> executionTime as a seed. we cannot depend on any pre-seeded sequence
>>> since this is a read and there is no guarantee it will occur again in
>>> same order.
>>>
>>> am i missing something ?
>>>
>>> On Mon, Mar 2, 2009 at 6:38 AM, Klaus Wuestefeld
>>> <[email protected]> wrote:
>>>> Stop thinking in terms of "reads which modify data" and think about it
>>>> as "lazy evaluation", which is perfectly ok. Something like this:
>>>>
>>>>
>>>> Object executeQuery(Date executionTime) {
>>>>
>>>>   synchronized (_system) {
>>>>      if (!isStateUpdatedTo(executionTime))
>>>>         updateStateWithReallyComplexAndPseudoRandomRulesTo(executionTime);
>>>>   }
>>>>
>>>>   return queryStateWhatever();
>>>> }
>>>>
>>>>
>>>> See you, Klaus.
>>>>
>>>> ------------------------------------------------------------------------------
>>>> Open Source Business Conference (OSBC), March 24-25, 2009, San Francisco, CA
>>>> -OSBC tackles the biggest issue in open source: Open Sourcing the Enterprise
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>>>
>>> ------------------------------------------------------------------------------
>>> Open Source Business Conference (OSBC), March 24-25, 2009, San Francisco, CA
>>> -OSBC tackles the biggest issue in open source: Open Sourcing the Enterprise
>>> -Strategies to boost innovation and cut costs with open source participation
>>> -Receive a $600 discount off the registration fee with the source code: SFAD
>>> http://p.sf.net/sfu/XcvMzF8H
>>> _______________________________________________
>>> To unsubscribe go to the end of this page: http://lists.sourceforge.net/lists/listinfo/prevayler-discussion
>>> _______________________________________________
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>>>
>>
>> ------------------------------------------------------------------------------
>> Open Source Business Conference (OSBC), March 24-25, 2009, San Francisco, CA
>> -OSBC tackles the biggest issue in open source: Open Sourcing the Enterprise
>> -Strategies to boost innovation and cut costs with open source participation
>> -Receive a $600 discount off the registration fee with the source code: SFAD
>> http://p.sf.net/sfu/XcvMzF8H
>> _______________________________________________
>> To unsubscribe go to the end of this page: http://lists.sourceforge.net/lists/listinfo/prevayler-discussion
>> _______________________________________________
>> "Databases in Memoriam" -- http://www.prevayler.org
>>
>
> ------------------------------------------------------------------------------
> Open Source Business Conference (OSBC), March 24-25, 2009, San Francisco, CA
> -OSBC tackles the biggest issue in open source: Open Sourcing the Enterprise
> -Strategies to boost innovation and cut costs with open source participation
> -Receive a $600 discount off the registration fee with the source code: SFAD
> http://p.sf.net/sfu/XcvMzF8H
> _______________________________________________
> To unsubscribe go to the end of this page: http://lists.sourceforge.net/lists/listinfo/prevayler-discussion
> _______________________________________________
> "Databases in Memoriam" -- http://www.prevayler.org
>

------------------------------------------------------------------------------
Open Source Business Conference (OSBC), March 24-25, 2009, San Francisco, CA
-OSBC tackles the biggest issue in open source: Open Sourcing the Enterprise
-Strategies to boost innovation and cut costs with open source participation
-Receive a $600 discount off the registration fee with the source code: SFAD
http://p.sf.net/sfu/XcvMzF8H
_______________________________________________
To unsubscribe go to the end of this page: http://lists.sourceforge.net/lists/listinfo/prevayler-discussion
_______________________________________________
"Databases in Memoriam" -- http://www.prevayler.org