[erlang-questions] Internal compiler atoms

Håkan Mattsson <>
Fri Jul 28 09:22:37 CEST 2017


You must have mis-understood what I wrote.

It is not my program that generates all those atoms. They are generated
internally by the compiler while it is compiling my program from forms. The
atoms my program are using do already exist in the forms data structure.

I am very well aware of the +t flag. But it is quite boring to set it to
100M just to be able to compile. As I do not understand why the compiler
dynamically generates all these internal atoms I cannot predict how big the
atom table needs to be. In my latest run the compiler actually generated
25M atoms (which is 25 times the default size of the atom table). It
surprised me.

Please, do not come up with further suggestions about avoiding explicit
creation of atoms in general. My question was much more specific.

/Håkan

On Jul 28, 2017 08:43, "Albin Stigö" <> wrote:

1. Try to avoid dynamically creating new atoms.

2. But I need to! Goto rule 1.

3. Dynamic atoms are not safe for long running code. You will
eventually exhaust the atom table and this will lead to subtle bugs.

4. If you really DO need to create dynamic atoms for a quick and dirty
hack, keep in mind that atoms with a common prefix ie. foo_1, foo_2,
foo_3 etc will lead worse performance because of how erlang compares
atoms (some Erlang guru correct me if I'm wrong but this used to be
the case).


--Albin


On Fri, Jul 28, 2017 at 8:23 AM, Valentin Micic <>
wrote:
>
> Is this anything that can be disabled?
>
> Say that there is, very soon you would be asking: why is there a limit on
a
> number of atoms?
> Instead, you should write a code that does not generate 700k atoms.
>
> V/
>
>
> _______________________________________________
> erlang-questions mailing list
> 
> http://erlang.org/mailman/listinfo/erlang-questions
>
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