Docs build exceeds the RAM limit on ReadtheDocs

[rw1nkler]

The build on ReadtheDocs server exceeds the RAM limit:
https://readthedocs.org/projects/symbiflow/builds/10499598/

This is caused by the conda environment and is a well-known issue:
readthedocs/readthedocs.org#6412 (comment)

Nevertheless, If we want to use Doxygen on ReadtheDocs we will need conda. Fortunately, In many cases, people from RTD increased the amount of RAM memory for a specific project. Maybe we should ask them for it?

https://docs.readthedocs.io/en/stable/guides/build-using-too-many-resources.html#requests-more-resources

[rw1nkler]

It seems that conda itself uses a lot of RAM. Here are results of profiling the conda environment creation process:

1. Conda with all channels:

environment.yml:

name: SymbiFlow-docs
channels:
  - symbiflow
  - conda-forge
  - defaults
dependencies:
  - doxygen
  - cmake
  - pygobject
  - cairo
  - pango
  - pip
  - pip:
    - -r file:requirements.txt

2. Conda only with conda-forge channel:

environment.yml:

name: SymbiFlow-docs
channels:
  - conda-forge
dependencies:
  - doxygen
  - cmake
  - pygobject
  - cairo
  - pango
  - pip
  - pip:
    - -r file:requirements.txt

3. Conda only with pip and with reduced number of dependencies:

environment.yml:

name: SymbiFlow-docs
channels:
  - symbiflow
  - conda-forge
  - defaults
dependencies:
  - pip
  - pip:
    - -r file:requirements.txt

requirements.txt:

Sphinx==2.0.0

Profiled using:

mprof run --interval 0.01 --include-children ./build/conda/bin/conda env create -q -f environment.yml`

[rw1nkler]

I've asked the RTD team, and we now have 1.5 Gb of RAM for the building process.
It seems that this is enough because the build is passing. I will close the issue.

[mithro]

@rw1nkler Did you get the memory increased for all the symbiflow related repos?

[rw1nkler]

@mithro I've asked them only for this repository.