difference between MaDictionary and MagmaDictionary

[Ching de la Serna]

Hi Chris,

Would a MagmaPreallocatedDictionary be suitable for a collection of say, 100
million names and addresses?

ching

On Wed, Dec 15, 2010 at 10:00 AM, Chris Muller <asqueaker at gmail.com> wrote:

> MagmaDictionary is just a normal MagmaCollection with an index on
> #hash (actually, #hash32 because its just a 32-bit index).  Please see
> it in a hierarchy browser.  As a subclass of MagmaCollection, it
> inherits its characteristics...  Which is actually unfortunate because
> those characteristics of regular MagmaCollections have highest
> throughput when answering _batches_ of rows.  But dictionary's are
> accessed by #at:, just one object at a time.
>
> This is why I wrote MagmaPreallocatedDictionary.  It is based on a
> MagmaArray.
>
> A MagmaArray is an auto-growing, but never shrinking, Array that can
> be very large.  Please see the test cases whichh reference MagmaArray
> for the actual semantics.
>
> MagmaArrays are as fast as possible, always just two disk seeks,
> 6-bytes each, to get the location of the contents of any object.
> That's why MagmaPreallocatedDictionary is much faster than a
> MagmaCollection, which is based on a MaHashIndex file-structure for
> supporting range-based querying.
>
>  - Chris
>
>
>
>
> On Tue, Dec 14, 2010 at 4:57 PM, Esteban Lorenzano <estebanlm at gmail.com>
> wrote:
> > ok, and what about using MagmaDictionary? better? or the same?
> >
> > cheers,
> > Esteban
> >
> > El 14/12/2010, a las 5:40p.m., Chris Muller escribió:
> >
> >>>> If I replace MaDictionary with Dictionary, I will be reading/writing
> the
> >>>> full dictionary each time I add an element to the dictionary... isn't?
> >>
> >> Yes, that's true.  But a MaDictionary only saves you that if you have
> >> a lot of collisions.
> >>
> >>> I think that you need replace MaDictionary with
> MagmaPreallocatedDictionary
> >>> not with standard Dictionary.
> >>
> >> No, this is wrong, please see how MagmaPreallocatedDictionary works.
> >> It is for very large dictionary's, Esteban is using a MaDictionary for
> >> his root object, and my guess is it only has a few entries in it..
> >>
> >> - Chris
> >
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