Improve job-distribution with a mix of timed & untimed files

Author: jdelStrother

lib/flatware/rspec/job_builder.rb

@@ -43,11 +43,16 @@ def jobs
       private
 
       def balance_jobs(bucket_count:, timed_files:, untimed_files:)
-        balance_by(bucket_count, timed_files, &:last)
-          .map { |bucket| bucket.map(&:first) }
-          .zip(
-            round_robin(bucket_count, untimed_files)
-          ).map(&:flatten)
+        timed_groups = balance_by(bucket_count, timed_files, &:last)
+                       .map { |bucket| bucket.map(&:first) }
+        untimed_groups = round_robin(bucket_count, untimed_files)
+
+        # When the files can't be evenly divided between groups, the first groups
+        # in each of timed_groups & untimed_groups will have more files.
+        # By reversing one of them before combining them, we can improve the final distribution.
+        timed_groups
+          .zip(untimed_groups.reverse)
+          .map(&:flatten)
           .reject(&:empty?)
           .map { |files| Job.new(files, args) }
       end

spec/flatware/rspec/job_builder_spec.rb

@@ -80,8 +80,9 @@
       it "doesn't return empty job-groups" do
         expect(subject).to match_array(
           [
-            have_attributes(id: include('./slow_spec.rb', './new_1_spec.rb')),
-            have_attributes(id: include('./fast_1_spec.rb'))
+            have_attributes(id: include('./fast_1_spec.rb')),
+            have_attributes(id: include('./slow_spec.rb')),
+            have_attributes(id: include('./new_1_spec.rb'))
           ]
         )
       end