[rules-users] Rule using accumulate

[Andrés Corvetto]

The problem with this approach is that a Bid may not always match the head
of the list, because the price of the head Offer could be higher.
Given a Bid, I need to match it with the oldest Offer with equal o lower
price, and that Offer could be in any index of the list.
(Note that the previous approach did work, just not very efficiently)

- Andres

On Wed, Apr 28, 2010 at 6:13 AM, Wolfgang Laun <wolfgang.laun at gmail.com>wrote:

> Here is another way of matching Offers first-in first. It is based on
> a linked list connecting new Offers the way they arrive. You'll need
> another WME OfferList containing references to the head of the list
> and to the last element. An unlinked new Offer is added at the end.
> Matching is now done by looking at the "head" field of the OfferList
> WME, and a matched Offer is removed from the list. You'll probably
> need another field in an Offer to indicate the status (new, unmatched,
> matched) so that you don't get cycles in your loop firings.
>
> -W
>
> On Wed, Apr 28, 2010 at 3:43 AM, Andres Corvetto <acorvetto at gmail.com>
> wrote:
> >
> > Thank you for your answers.
> >
> > I tried this approach (which yields much more elegant rules), but i'm
> afraid
> > it does not perform very well.
> > If I insert 10000 Offers and then 1 bid, it takes too much time to
> execute.
> > If understand correctly it's because of the  "not Offer(creationTimestamp
> <
> > $ct)"  clause in the LHS, which forces a comparison of every matching
> Offer
> > against every other Offer.
> >
> > The motivation for my original post was to find a way of achieving the
> > results of an accumulator without having to sort all the matching Offers
> by
> > creationTimestamp.
> > Going back to that first approach (using an accumulator), I found that
> > Drools feeds the accumulator with the matching Offers in reverse order
> (ie,
> > newest first, LIFO).
> > Is this a natural consequence of the way facts are stored in the working
> > memory or is there a way of changing this behaviour (so that oldest are
> > feeded first, FIFO)?
> >
> > Thanks again
> >
> > - Andres
> >
> > --
> > View this message in context:
> http://drools-java-rules-engine.46999.n3.nabble.com/Rule-using-accumulate-tp757311p761181.html
> > Sent from the Drools - User mailing list archive at Nabble.com.
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