I see no reason why standard tree locking algorithms
(SIX locks) cannot be applied to Judy.
Thx,
dk
----- Original Message -----
From: "Alan Silverstein" <[EMAIL PROTECTED]>
To: <[email protected]>; <[EMAIL PROTECTED]>
Sent: Friday, March 23, 2007 8:59 AM
Subject: PS about locking Judy arrays
> PS about locking inside Judy arrays. Late in the project we did
> consider thread issues, which is why we spent time studying the matter
> and writing the text/example program. Since Judy is a digital tree,
> certainly it's theoretically possible to add locking info to tree nodes
> and lock/synchronize subtrees.
>
> But performance is a funny business. Judy is highly tuned for
> speed/space performance while remaining as portable as possible.
> (Unfortunately we learned too late about knowing only dependent
> attributes, such as endianness, not platform types, but that's another
> story.) The time required to thread lock swamps average Judy operation
> times, if I recall right. The space required to add thread locking
> would swamp Judy's low average bytes per index. You'd give back most of
> what it buys you!
>
> So if at all possible, avoid the need to thread-sync, and if you must,
> try doing it at the whole-array level first.
>
> Bear in mind that one unobvious feature Judy buys you is huge but
> efficient meta-tries, that is, where every node is itself a Judy array
> handling one word (32 or 64 bits) of a longer key value. That's how
> JudySL works. Nothing prevents you from thread locking whole arrays in
> the meta-trie, and pretending each Judy array is an atomic object.
>
> Alan
>
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