----- Original Message -----
From: "James Strachan" <[EMAIL PROTECTED]>
To: "Jakarta Commons Developers List" <[EMAIL PROTECTED]>;
"Morgan Delagrange" <[EMAIL PROTECTED]>
Sent: Friday, February 15, 2002 10:47 AM
Subject: Re: [collections][PATCH] LRUMap - license, docs update


> ----- Original Message -----
> From: "Morgan Delagrange" <[EMAIL PROTECTED]>
> > ----- Original Message -----
> > From: "Michael Smith" <[EMAIL PROTECTED]>
> > To: "Jakarta Commons Developers List" <[EMAIL PROTECTED]>
> > Sent: Friday, February 15, 2002 7:41 AM
> > Subject: RE: [collections][PATCH] LRUMap - license, docs update
> >
> >
> > > -----Original Message-----
> > > From: James Strachan [mailto:[EMAIL PROTECTED]]
> > > > ----- Original Message -----
> > > > From: "Michael Smith" <[EMAIL PROTECTED]>
> > > > > > Maybe renaming it to FastLRUMap that approximates LRU but
> > > > > > isn't totally
> > > > > > accurate in all circumstances might help?
> > > > >
> > > > > To me, that makes it even more confusing.
> > > >
> > > > OK how about calling it LFUMap - "least frequently used"
> > > > which seems a more
> > > > accurate description of the algorithm than "least recently used".
> > >
> > > I think for now, we're really kind of stuck with the name.  We'll need
> > > to maintain the name for Collections 1.x to maintain API
compatibility.
> > >
> > > Morgan has done a little work on LRUMap recently.  I haven't gotten
the
> > > chance to take a peek, but maybe he fixed the bubble list so it really
> > > is a least recently used?  Morgan, can you confirm/deny?
> > >
> >
> > Nope, haven't fixed the bubble list yet.  It's implemented as an
> ArrayList,
> > which makes it impractical to move elements to the front.  I'll need to
> > reimplement it as a LinkedList, TreeSet or something similar.  I think
> it's
> > worthwhile to make this class true LRU though.
>
> Agreed. I originally went with the bubble list for efficiency but I guess
a
> LinkedList isn't too bad these days.
>
> Would using a LinkedList and moving it to the front (rather than bubbling
up
> one) make the LRUMap 'least recently used' or would folks still think of
it
> as 'least frequently used'.
>
> James
>

IMO, moving an item to the front upon any get or put is precisely what is
implied by LRU.  I think someone may want to take on a LFUMap class too, but
that's much more complicated.

- Morgan


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