feat: support mersenne twister

lib/numo/random/generator.rb

@@ -24,10 +24,14 @@ class Generator # rubocop:disable Metrics/ClassLength
       # Creates a new random number generator.
       #
       # @param seed [Integer] random seed used to initialize the random number generator.
-      # @param algorithm [String] random number generation algorithm ('pcg32', 'pcg64').
-      def initialize(seed: nil, algorithm: 'pcg64')
+      # @param algorithm [String] random number generation algorithm ('mt32', 'mt64', 'pcg32', and 'pcg64').
+      def initialize(seed: nil, algorithm: 'pcg64') # rubocop:disable Metrics/MethodLength
         @algorithm = algorithm.to_s
         @rng = case @algorithm
+               when 'mt32'
+                 MT32.new(seed: seed)
+               when 'mt64'
+                 MT64.new(seed: seed)
                when 'pcg32'
                  PCG32.new(seed: seed)
                when 'pcg64'

spec/numo/random/generator_spec.rb

@@ -6,12 +6,21 @@
   let(:algorithm) { 'pcg64' }
 
   describe '#initialize' do
-    context "when algorithm args is 'pcg64'" do
-      let(:algorithm) { 'pcg64' }
+    context "when algorithm args is 'mt32'" do
+      let(:algorithm) { 'mt32' }
 
-      it 'uses PCG32 class for random number generator', :aggregate_failures do
-        expect(rng.algorithm).to eq('pcg64')
-        expect(rng.instance_variable_get(:@rng)).to be_a(Numo::Random::PCG64)
+      it 'uses MT32 class for random number generator', :aggregate_failures do
+        expect(rng.algorithm).to eq('mt32')
+        expect(rng.instance_variable_get(:@rng)).to be_a(Numo::Random::MT32)
+      end
+    end
+
+    context "when algorithm args is 'mt64'" do
+      let(:algorithm) { 'mt64' }
+
+      it 'uses MT64 class for random number generator', :aggregate_failures do
+        expect(rng.algorithm).to eq('mt64')
+        expect(rng.instance_variable_get(:@rng)).to be_a(Numo::Random::MT64)
       end
     end
 
@@ -24,6 +33,15 @@
       end
     end
 
+    context "when algorithm args is 'pcg64'" do
+      let(:algorithm) { 'pcg64' }
+
+      it 'uses PCG64 class for random number generator', :aggregate_failures do
+        expect(rng.algorithm).to eq('pcg64')
+        expect(rng.instance_variable_get(:@rng)).to be_a(Numo::Random::PCG64)
+      end
+    end
+
     context 'when wrong algorithm args given' do
       let(:algorithm) { 'none' }