[erlang-questions] Re: ets traversal time
Thu Jul 16 17:01:08 CEST 2009
Jim Morris wrote:
> Have you tried ets:foldl which is tail recursive (presumably as it
> does not specify in the docs, but it is in lists:foldl) or is there a
> reason to use foldr?
> If foldr is not tail recursive then I suspect that with 20K entries
> the stack will get used up and or eat a lot of memory which needs to
> be allocated and released, maybe even causing swapping to the disk.
The only difference between ets:foldl and ets:foldr is that foldl
uses first/next and foldr uses last/prev. Apart from that, they
are exactly the same. See ets.erl
If the ets table is a 'set', last() -> first() and prev() -> next(),
since there is no defined ordering in hash tables. See erl_db_hash.c.
If there is a difference in the timings, I would first try to
rule out measurement error or see if it falls within the margin
of error for the measurement.
CTO, Erlang Training & Consulting Ltd
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