[erlang-questions] Re: Unicast 20k messages, $500-$1000 bounty

Paulo Sérgio Almeida <>
Thu Jul 16 17:35:02 CEST 2009


Joel Reymont wrote:
>
> Also, instead of duplicating the table data by building a list, why not 
> use ets:first and ets:next?

To be sure one has to measure. But my intuition is that select followed 
by list traversal avoids a ping-pong between built-in and user code. It 
will use a built-in function (C) to operate in bulk over the table, 
extracting only what is needed. Then you just traverse the list; and 
Erlang is very good operating on lists.

Also the list produced should be quite compact, with good memory 
locality. <- Is this true?

Also, the negative impact due to GC should be later, after the messages 
have been sent. But in this case not even GC is a problem as the process 
exits after sending the msgs.

Btw, now I noticed a pontential problem. I don't know what deliveery 
semantics you aim for, but now you don't have total order in message 
delivery even for the same topic. As the sending is in a spawned proc, 
two clients can receive two msgs A and B from the same topic one in the 
order A -> B and the other B -> A. As you already have middleman, why 
not do the sending without spawning a proc?

Regards,
Paulo


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