[erlang-bugs] Inserting new keys into maps is very slow (R17rc1)

[Dan Gudmundsson]

Large maps are currently not optimized, that part is not implemented yet,
you should currently only use them for less than 100 keys...

It is on the todo list..


On Thu, Feb 6, 2014 at 10:28 PM, McDowell, Edward D. <EMcDowell@REDACTED>wrote:

> maps:put/3 in R17rc1 on Windows (64 bit) runs slowly when a
>
> large number of randomly generated keys are inserted into a
>
> map.  The following table shows that the time to insert n
>
> keys grows quadratically, so the time to insert a single key
>
> grows linearly.  Note that performance is greatly improved
>
> by using a dict (from stdlib).
>
>
>
> Number    Insert into map   Insert into dict
>
> of keys   (milliseconds)    (milliseconds)
>
> 10000           969                16
>
> 20000          4031                62
>
> 40000         15937               172
>
> 80000         63734               453
>
>
>
> The following code was used for these tests.  The dict
>
> tests used the same code with dict:new/0 and dict:store/3
>
> replacing maps:new/0 and maps:put/3, respectively.
>
>
>
> -module(testmap).
>
> -export([start/1]).
>
>
>
> loop(Map, 0) -> Map;
>
> loop(Map, Times) ->
>
>     Key = random:uniform(999999),
>
>     loop(maps:put(Key, true, Map), Times - 1).
>
>
>
> start(NumKeys) ->
>
>     {A, B, C} = now(),
>
>     random:seed(A, B, C),
>
>     Before = (1000000 * A + B) * 1000 + C div 1000,
>
>     loop(maps:new(), NumKeys),
>
>     {E, F, G} = now(),
>
>     After = (1000000 * E + F) * 1000 + G div 1000,
>
>     io:format("Elapsed time: ~w milliseconds.~n",
>
>       [After - Before]).
>
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>
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