Hi Bruce,
Try `into` instead of `concat`.
Applying concat to growing data is like "Schlemiel the Painter's
algorithm".

Cheers.

On 2月1日, 午後4:19, bruce li <leilmy...@gmail.com> wrote:
> Hello, everyone. I'm experience some performance issue when using clojure.
> The scenario is as follows:
>
> I have a huge list of xls files to process. I used the
> org.clojars.boechat107/cloxls  to read the files which for each file
> generates a list(approximately 65,000 elements). Now I need to concatenate
> all of them. I used (mapcat read-worksheet files) to get the final list,
> but it soon reports out of heap space. Then I tried to use mutable
> structures:
>
>   (doseq [f files]
>     (swap! sheet concat (read-worksheet f)))
>
> where sheet is defined as (def sheet (atom [])))
>
> But the concat seems to slow down a lot when the list grows larger. I'm
> wondering if in clojure there is some efficient idiom to handle such
> situation such as efficient concatenation?
>
> Thanks,
> Bruce Li

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