Are data structure with repeated pointers replicated when sent as a message


Sorry for the bad title but I did not know how to express that well. Let me explain:

I believe that if I assign a same value to different locations in a data structure, the value is only at one memory address but its pointer is copied. For example:

v = 1
m = %{a: v, b: v}

I believe that the value bound to v and to two map keys occupies a single memory space, but there are multiple pointers to that value. Please correct me if I’m wrong.

If this is true, my question is: What happens when I send my map to another process ? Does the memory structure gets replicated, or is the 1 duplicated in two memory spaces ?

Thank you

(A bit of context, but you can skip that)
I have a large “project” data structure, a map, with some key/values containing generic configs, etc. And one key that contains a list of reports configs. For convenience, I map over the reports configs, copying all the generic config into each report config so, when generating a report, I have my needed data around. I do this copying in the process that must send reports for a particular “project”. But I wonder if I could just copy all that stuff once, for all projects, when I load the configuration initially, and the process that must handle a particular process would receive the reports configs with all generic data into each report config already.

Of course, I am not talking about megabytes here, in practice it does not change much, I do not really care about performance at that point. But it made me wonder.

Also I could use persistent terms here, but again perfs do not matter at the moment.

Hi! Sharing is not preserved when sending a message to another process.

See “Loss of sharing” under

The BEAM book also discusses this:

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Perfect, thank you :slight_smile: