Test Native and GSL Implementations

[mkasberg]

classifier-reborn is designed to work with or without
GSL support.

classifier-reborn/docs/index.md

Line 68 in 99d13af

Note that `LSI` will work without these libraries, but as soon as they are installed, classifier will make use of them. No configuration changes are needed, we like to keep things ridiculously easy for you.

If GSL is installed, classifier-reborn will detect it and use it. If GSL
is not installed, classifier-reborn will fall back to a pure-ruby
implementation. The mechanism for doing so is in lsi.rb:

classifier-reborn/lib/classifier-reborn/lsi.rb

Lines 7 to 17 in 99d13af

	begin
	raise LoadError if ENV['NATIVE_VECTOR'] == 'true' # to test the native vector class, try `rake test NATIVE_VECTOR=true`
	require 'gsl' # requires https://github.com/SciRuby/rb-gsl
	require_relative 'extensions/vector_serialize'
	$GSL = true
	rescue LoadError
	$GSL = false
	require_relative 'extensions/vector'
	require_relative 'extensions/zero_vector'
	end

I think it's important to test the classifier-reborn gem with GSL
support in CI. One of my goals is to add similar support using Numo,
and I'd like that to be tested in CI as well. Also, I want to make sure I
don't do anything along the way that could break existing GSL support.
As far as I can tell, GSL support was never tested in CI before now
(though it was previously discussed
here).

In this PR, I'm expanding our text matrix to test with and without GSL
enabled. When the matrix has GSL enabled, we install the gsl gem
(which is not included in our Gemfile since it's optional). Lucky for
us, GitHub already includes libgsl as pre-installed
software,
so we don't need to do anything special for the apt package. Our gem
already has everything needed to build & install. When matrix.gsl is
false, we won't install the gem and tests will run the native Ruby
implementation. When matrix.gsl is true, we'll install the gem tests
will run the GSL implementation.

Currently, GSL only works with Ruby 2.7. (One of the main reasons I want
to add support for Numo is because GSL is becoming difficult to
support.) As such, I've excluded other versions of ruby in our test
matrix for now. They'll still be tested with GSL disabled, but not with
it enabled.

While working on this, I noticed some tests in the LSI spec that return
early when $GSL is not enabled. It would be better for those tests to
report as skipped when GSL is not enabled (and this matches the pattern
of the redis tests, that report as skipped if redis isn't available).

[mattr-]

@jekyllbot: merge +dev

[mattr-]

Thanks! This is a great improvement!

[ashmaroli]

@mkasberg I think there is some misunderstanding here.

The lone job that runs with gsl: true installs the gsl gem in a separate step using gem install ... However, the test suite is consequently run with bundle exec .., meaning the test-suite is run in the context of pre-existing Gemfile.lock (that does not include ``gsl` gem).

Theoretically, my argument can be proven / disproved by having the test-helper issue an appropriate log output before running the tests.

To remove the ambiguity nevertheless, the best route is to have Bundler install the gsl gem during bundle install by using an environment variable:

# Gemfile

gem 'gsl' if ENV["LOAD_GSL"]

And then initialize the environmental variable before setting up Ruby:

# workflow config

jobs:
  ci:
    env:
      # See https://github.com/marketplace/actions/setup-ruby-jruby-and-truffleruby#matrix-of-gemfiles
      BUNDLE_GEMFILE: ${{ matrix.gemfile }}
      LOAD_GSL: ${{ matrix.gsl }}

[mkasberg]

You're right! These two tests should not be skipped when GSL is actually loaded:

Thanks for the suggestion, I think I can implement something like that and I'll make a PR to do so! Might take me about a week to get to it, I'm going on vacation this week.