Erlang Term Info (Memory Consumption)
=====================================

[![Build Status](https://secure.travis-ci.org/okeuday/erlang_term.png?branch=master)](http://travis-ci.org/okeuday/erlang_term)

Purpose
-------

To provide the in-memory size of Erlang terms, ignoring where the Erlang terms
are stored.

Size information should match the [Erlang Efficiency Guide memory information](http://www.erlang.org/doc/efficiency_guide/advanced.html#id68923):

* Small integer: 1 word
  * On 32-bit architectures: -134217729 < i < 134217728 (28 bits)
  * On 64-bit architectures: -576460752303423489 < i < 576460752303423488 (60 bits)
* Big integer: 3..N words
* Atom: 1 word
* Float:
  * On 32-bit architectures: 4 words
  * On 64-bit architectures: 3 words
* Binary: 3..6 + data
* List: 1 word + 1 word per element + the size of each element
* Tuple: 2 words + the size of each element
* Small Map (N =< 32): 5 words + the size of all keys and values
* Large Map (N > 32): N * [1.6 .. 1.8] + the size of all keys and values
* Pid:
  * From local node: 1 word
  * From remote node: 5 words
* Port:
  * From local node: 1 word
  * From remote node: 5 words
* Reference:
  * On 32-bit architectures:
    * From local node: 5 words
    * From remote node: 7 words
  * On 64-bit architectures:
    * From local node: 4 words
    * From remote node: 6 words
* Fun: 9..13 words + size of environment
* Erlang process: 338 words when spawned (includes a heap of 233 words)

Limitations
-----------

* Binaries are not tracked to avoid counting a reference more than once
  (to avoid the extra latency and memory use)

License
-------

MIT License

Contact
-------

Michael Truog (mjtruog at protonmail dot com)

Thanks
------

* Sverker Eriksson [`erts_debug:flat_size/1` info](erlang_bugs_email.txt)

