🚀 Change mopti gem to non-rutime dependent library

Gemfile

@@ -5,6 +5,7 @@ gemspec
 
 gem 'coveralls', '~> 0.8'
 gem 'mmh3', '>= 1.0'
+gem 'mopti', '>= 0.1.0'
 gem 'numo-linalg', '>= 0.1.4'
 gem 'parallel', '>= 1.17.0'
 gem 'rake', '~> 12.0'

lib/rumale/metric_learning/neighbourhood_component_analysis.rb

@@ -2,13 +2,15 @@
 
 require 'rumale/base/base_estimator'
 require 'rumale/base/transformer'
-require 'mopti/scaled_conjugate_gradient'
 
 module Rumale
   module MetricLearning
     # NeighbourhoodComponentAnalysis is a class that implements Neighbourhood Component Analysis.
     #
     # @example
+    #   require 'mopti'
+    #   require 'rumale'
+    #
     #   transformer = Rumale::MetricLearning::NeighbourhoodComponentAnalysis.new
     #   transformer.fit(training_samples, traininig_labels)
     #   low_samples = transformer.transform(testing_samples)
@@ -63,6 +65,8 @@ def initialize(n_components: nil, init: 'random', max_iter: 100, tol: 1e-6, verb
       # @param y [Numo::Int32] (shape: [n_samples]) The labels to be used for fitting the model.
       # @return [NeighbourhoodComponentAnalysis] The learned classifier itself.
       def fit(x, y)
+        raise 'NeighbourhoodComponentAnalysis#fit requires Mopti but that is not loaded.' unless enable_mopti?
+
         x = check_convert_sample_array(x)
         y = check_convert_label_array(y)
         check_sample_label_size(x, y)
@@ -98,6 +102,14 @@ def transform(x)
 
       private
 
+      def enable_mopti?
+        if defined?(Mopti).nil?
+          warn('NeighbourhoodComponentAnalysis#fit requires Mopti but that is not loaded. You should intall and load mopti gem in advance.')
+          return false
+        end
+        true
+      end
+
       def init_components(x, n_features, n_components)
         if @params[:init] == 'pca'
           pca = Rumale::Decomposition::PCA.new(n_components: n_components, solver: 'evd')

rumale.gemspec

@@ -45,5 +45,4 @@ Gem::Specification.new do |spec|
   }
 
   spec.add_runtime_dependency 'numo-narray', '>= 0.9.1'
-  spec.add_runtime_dependency 'mopti', '>= 0.1.0'
 end

spec/rumale/metric_learning/neighbourhood_component_analysis_spec.rb

@@ -80,6 +80,19 @@
     end
   end
 
+  context 'when Mopti is not loaded' do
+    before do
+      @backup = Mopti
+      Object.send(:remove_const, :Mopti)
+    end
+
+    it 'raises Runtime error' do
+      expect { transformer.fit(x, y) }.to raise_error(RuntimeError)
+    end
+
+    after { Mopti = @backup }
+  end
+
   it 'dumps and restores itself using Marshal module.', :aggregate_failures do
     copied = Marshal.load(Marshal.dump(transformer.fit(x, y)))
     expect(copied.class).to eq(transformer.class)

spec/spec_helper.rb

@@ -15,6 +15,7 @@
 require 'rumale'
 require 'parallel'
 require 'mmh3'
+require 'mopti'
 
 def two_clusters_dataset
   rng = Random.new(8)