On Wednesday, 4 September 2013 10:00:42 UTC+8, Brian Craft wrote:
> I'm loading data files of about 1-2G, which are composed of a bunch of
> numeric data blocks. I need to store the data blocks w/o storing
> duplicates. They arrive as vectors of floats, and are stored as primitive
> byte arrays.
>
> I first tried memoizing the function that saves a block (returning an id),
> with the core memoize function. This failed because every block became a
> different key in the memoization, regardless of the content. It looks like
> clojure treats variables referencing primitive arrays as equal only if they
> refer to the same array. Note:
>
> cavm.core=> ({[1 2 3] "foo"} [1 2 3])
> "foo"
> cavm.core=> ({(float-array [1 2 3]) "foo"} (float-array [1 2 3]))
> nil
> cavm.core=> (let [a (float-array [1 2 3])] ({a "foo"} a))
> "foo"
>
>
>
> I next tried memoizing over the vector of floats, however performance
> became pathologically slow, and the process threw an OOM. I'm guessing this
> is due to the memory requirements of a clojure vector of floats vs. a
> primitive array of bytes holding the same data. Is there an easy way to
> compare the storage requirements?
>
> Any suggestions on how better to handle this?
>
You may want to use the :ndarray-float array implementation in the latest
version of core.matrix.
This is effectively a wrapper over a raw Java float array: so your storage
requirement should be close to the size of the raw byte data (assuming the
data blocks are large enough that the size of the wrapper is negligible)
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