Hi Florian,
The ability to tell JESS: "I am going to do some changes but wait before
you start firing" or "please stop firing any new rule until I tell you" or
"tell me when you have no more rule to fire" is in my opinion very
valuable.
Totally agreed. It's not that apparent or inconvenient for user to implement
these logic.
BTW, if you don't mind, could you send your copy of JessManager to me so
that I can study it a bit. I don't need all those details since I just need
a skeleton to understand how you did that.
Thanks!
Paul
From: "Florian Fischer" <[EMAIL PROTECTED]>
Reply-To: [email protected]
To: [email protected]
Subject: Re: JESS: How do I determine Jess engine has finished firing rules
Date: Tue, 13 Feb 2007 14:15:54 +0100
I actually went so far as to write a "JessManager" class that interfaces
JESS with my application.
It is a class that owns and runs a Rete engine when needed.
It provides functions to add and remove Java objects as facts. It listens
to the objects propertyChanges to be notified of changes.
It has a separate thread that runs the Rete engine as necessary. The
thread usually sleeps but is notified as soon as a fact was changed. Why
not just call runUntilHalt()? Because this way, I can add flags telling
whether a run is in progress and a monitor to wait for the run to stop.
With the same monitor I can start and end something like a transaction to
do changes to my facts while JESS is not running. This way I can add
multiple related facts without JESS interfering by firing rules at the same
time.
It also has a startup and shutdown procedure.
Unfortunately my JessManager has many dependencies with the rest of the
application so that it would require some work to make it standalone and
useable it in a different application. For instance, it can only add facts
that are subclasses of the "generic data object" class of my application.
But while writing that class, I was wondering if there wasn't or shouldn't
be something like that in JESS. The ability to tell JESS: "I am going to
do some changes but wait before you start firing" or "please stop firing
any new rule until I tell you" or "tell me when you have no more rule to
fire" is in my opinion very valuable.
Regards,
Florian Fischer
Shi Paul wrote:
Hi Henrique and others,
Ernest's reply is only good for single thread execution, while I have at
least 2 threads running. It's kinda like reproducer/consumer scenario. I
have Jess running in its own thread (consumer thread), I have my other
threads running as facts-collecting threads (producer thread). So once
those facts-collecting threads stop running, I need to stop Jess thread
but the problem is when I call Rete.halt() I don't know if it's still
busy.
I tried Rete.listActivations() before stopping it, it seems doesn't work
as well (the test result revealed that). I didn't try Scott's suggestion
since I want the solution in the API level instead of adding a new rule in
the knowledge base as I think the solution shouldn't be across 2 different
domains. Does anybody has othe good suggestions?
Thanks,
Paul
From: "Henrique Lopes Cardoso" <[EMAIL PROTECTED]>
Reply-To: [email protected]
To: [email protected]
Subject: Re: JESS: How do I determine Jess engine has finished firing
rules
Date: Mon, 12 Feb 2007 09:43:05 +0000
Why don't you use Rete.run() instead of runUntilHalt() and wait for the
method to return?
Read Ernest's reply.
Cheers,
Henrique
Shi Paul wrote:
Hmmm, I wouldn't say it's a nice solution although it might work. I
looked through the Rete api, there is a Rete.listActivations, I'm
wondering if I could count on that, before calling rete.halt in the main
thread, I'd use that API in a while loop and let main thread sleep for a
few seconds if that doesn't return 0.
From: "Krasnigor, Scott L (N-AST)" <[EMAIL PROTECTED]>
Reply-To: [email protected]
To: [email protected]
Subject: RE: JESS: How do I determine Jess engine has finished firing
rules
Date: Fri, 09 Feb 2007 15:59:11 -0500
The easiest thing to do is add a rule with a low salience (I use -1000)
that will always match and add whatever action on the rhs that you want
to use to signal all rules are done being processed. This rule will
always be added to the end of the agenda, so when it fires, you know
there are no more rules waiting to be fired.
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
On Behalf Of Shi Paul
Sent: Friday, February 09, 2007 1:46 PM
To: [email protected]
Subject: Re: JESS: How do I determine Jess engine has finished firing
rules
Hi,
Actually I have created its own thread and then in that thread I call
rete.runUntilHalt. Then I run into this issue just mentioned, can you
give
me some more specifics about the solution as how to determin if the
engine
is not busy and can safely be stopped? I'd imagine that the main thread
could just wait on some semaphore the jess thread operates or call into
some
API which does the same thing.
Thanks,
Paul
>From: "Ernest Friedman-Hill" <[EMAIL PROTECTED]>
>Reply-To: [email protected]
>To: [email protected]
>Subject: Re: JESS: How do I determine Jess engine has finished firing
rules
>Date: Fri, 9 Feb 2007 13:19:29 -0500
>
>
>On Feb 9, 2007, at 12:15 PM, Shi Paul wrote:
>
>>Hi there,
>>Is there an API to determine the rule engine has completed its
work.
I'd
>>like to call rete.halt() to stop the engine, but I'm wondering what
if
>>the engine is still firing rules when I call that. Can anybody shed
some
>>lights on it?
>>
>
>Jess doesn't create any threads on its own. If you call rete.run(),
then
>run() returns when, and only when, there are no more rules to fire.
If
you
>have multiple threads, then you can set up your own notification
scheme
>based on that.
>
>
>---------------------------------------------------------
>Ernest Friedman-Hill
>Advanced Software Research Phone: (925) 294-2154
>Sandia National Labs FAX: (925) 294-2234
>PO Box 969, MS 9012 [EMAIL PROTECTED]
>Livermore, CA 94550 http://www.jessrules.com
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