[erlang-questions] Fwd: Erlang "memory economics" & pointers pointing to other pointers

[Pablo Polvorin]

You might want to read
http://www.erlang.org/doc/efficiency_guide/processes.html#8.2.1
, the section on  "constant pool"

On 31 October 2014 19:14, Peter Johansson <flexchap@REDACTED> wrote:
>
> Hi there fellow Erlang-developers/users !
>
> I have been using Erlang in a project of mine for a couple of months (4 - 5)
> now ( coming from a 10 years Java & Python developer-background ) .....after
> having evaluating/investigating the language and its runtime-system first
> during some 1 - 2 months before the decision was taken that it address/suits
> my set of concluded needs very well indeed ( thumbs up for that  :-)   ).
>
> I'm directing these following few issues/questions towards,
> firstly/primarily, persons on the list which are members of or closely
> involved/related with the teams behind erlang.org and/or Erlang/OTP at
> Ericsson.
>
>
> The Erlang VM/architecture, as understood by me, aims/strives for keeping
> the amounts/occurrences of memory-copy operations to as low as possible.
> Natural exceptions to that being message-passing between processes .....and
> I/O - receive/write operations.
>
> My first and primary wondering ( or search for clarification on assumptions
> ....if you like ) is: ..... do this principle yields from the very first
> point of local existence ( loaded modules, function-declarations ) ??
>
> If I have say .... a list and a IOlist with elements of deterministic data:
>
> List = "blablabla".
> IOList = [<<"bla">>, <<"bla">>, <<"bla">>].
>
> Will List and IOlist be setup, within the heap-stack of an individual
> process, as pointers to the original memory-spaces of the lists from the
> module-load ??
>
> .....If these lists are used as included parts in later constructs
> .......will there then be new pointers setup in the process's heap-stack
> pointing to the previous ones ??
>
> Does this mechanism ( if it exist as of above ) re-emerge down/up through
> all the functional/operational levels of the process ( with socket-IO as the
> entry/exit-point ) ??
>
> Does this mechanism ( if it exist as of above ) yields for all Erlang's
> data/term-types .....or is any of those excluded from it ??
>
>
> If the mechanism exists as assumed so far ....the " in-mutative data-carrier
> " - property of Erlang becomes obvious/logical understandable for both
> performance & data-consistency reasons as I perceive the situation in a
> wider/extended context. An implication become that all concurrent processes
> within the node shares all originally deterministic data written to memory
> during module loads !?
>
> As an example ....everything assumed/concluded from this point on would
> essentially form the whole underlying foundation/reason for why the
> third-part library / module collection "ErlyDTL" is considered an attractive
> & high-performing tool for Output/Web- templating. It compiles templates to
> Erlang modules which then render their outputs from, as I have understood
> it, special IOlist-constructs holding alternating patterns/sequences of
> binaries ( fixed text part of original template ) & Funs (
> injection/condition/iterator -  statements of original template ). Only the
> outputs from these Funs then needs to be allocated/written into the
> heap-stack of the present process. Any further/later inclusive use of the
> result from the render-operation will, once again, cause new pointers - to -
> pointers to be setup in the process heap-stack.
>
>
> Under the condition that I have assumed/interpreted/understand this
> situation correctly ....I think ...indeed ...it should be formalized into a
> descriptive/introductory piece of information and put in a "front-line" /
> "early chapter"  place/position within the official Erlang/OTP documentation
> .... as it truly illustrates something that makes Erlang stand out
> extensively in relation to most other high-level languages.
>
> My practical impressions & experience of this language so far have been
> exclusively rewarding, encouraging & idea-producing for all the "next to
> come" motivations/objectives in my present time project.
>
> Sending my best regards for now / Peter   flexchap at gmail dot com
>
>
>
>
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-- 
Pablo Polvorin
ProcessOne