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Subject: Re: [boost] Boost container similar to Judy arrays?
From: Stewart, Robert (Robert.Stewart_at_[hidden])
Date: 2010-09-14 12:53:42

Christopher Jefferson wrote:
> On 7 Oct 2009, at 14:36, Achilleas Margaritis wrote:
> > Does boost have a container with similar properties to Judy
> > arrays? I searched the documentation but I did not find
> > anything similar.

I know of nothing like it in Boost.

> > Here is the Judy arrays home page:
> >
> >
> It is hard to find from a quick read. How is a Judy array
> different to using a std::map, with int as the indexing type? is a better link to follow.

According to that page:

"Some of the reasons Judy outperforms binary trees, b-trees, and skip-lists:

    * Judy rarely compromises speed/space performance for simplicity (Judy will never be called simple except at the API).
    * Judy is designed to avoid cache-line fills wherever possible. (This is the main design criteria for Judy.)
    * A b-tree requires a search of each node (branch), resulting in more cache-line fills.
    * A binary-tree has many more levels (about 8X), resulting in more cache-line fills.
    * A skip-list is roughly equivalent to a degree-4 (4-ary) tree, resulting in more cache-line fills.
    * An "expanse"-based digital tree (of which Judy is a variation) never needs balancing as it grows.
    * A portion (8 bits) of the key is used to subdivide an expanse into sub-trees. Only the remainder of the key need exist in the sub-trees, if at all, resulting in key compression."

The API is simple; the complexity, which sounds substantial, hides behind it. The data structure is highly adaptive to the data stored within it just based upon its design, or so it sounds.

Rob Stewart robert.stewart_at_[hidden]
Software Engineer, Core Software using std::disclaimer;
Susquehanna International Group, LLP

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