[erlang-questions] Erlang Cost Model

Joe Armstrong erlang@REDACTED
Wed Sep 16 18:56:32 CEST 2015

On Wed, Sep 16, 2015 at 5:03 PM, Eric des Courtis
<eric.des.courtis@REDACTED> wrote:
> What is the cost model of all operations in Erlang 18?
> For example Python has this cost model
> http://scripts.mit.edu/~6.006/fall07/wiki/index.php?title=Python_Cost_Model
> .
> I either want a link to a single source for this information or I would like
> to crowd source the information here now.

Interesting question - the problem with Erlang is that you cannot
ignore concurrency - so even if you know the costs of an atomic
operation in an isolated process I suspect this is not going to tell you
the cost when a few tens of thousands of processes perform that

 In a singly threaded language (like Python) I guess you could add costs
of atomic things together - but in Erlang it's more tricky.

I'd love to be able to reason like this:

     If process P1 takes time T1 and process P2 takes time T2

     then it might take time max(T1, T2) on a dual core and about
T1+T2 on a single core.

    But as soon as you start measuring these kind of things the interpretation
of the data becomes very difficult.

Not much help I'm afraid


> Thanks for your cooperation.
> Eric des Courtis
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