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@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@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
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