Benchmark require_relative.

It appears not to make a difference.

benchmarks/require_relative_boot.sh

@@ -0,0 +1,132 @@
+ruby -v
+
+echo "3 runs without require_relative, booting 100 times each run:"
+for i in {1..3}; do
+  time (for i in {1..100}; do ruby -Ilib:../rspec-support/lib -e "require 'rspec/core'"; done)
+done
+
+echo
+echo "3 runs with require_relative, booting 100 times each run:"
+export REQUIRE_RELATIVE=1
+for i in {1..3}; do
+  time (for i in {1..100}; do ruby -Ilib:../rspec-support/lib -e "require 'rspec/core'"; done)
+done
+
+: <<'result_comment'
+ruby 2.1.0p0 (2013-12-25 revision 44422) [x86_64-darwin12.0]
+3 runs without require_relative, booting 100 times each run:
+
+real  0m8.152s
+user  0m6.783s
+sys 0m1.149s
+
+real  0m8.023s
+user  0m6.689s
+sys 0m1.133s
+
+real  0m8.024s
+user  0m6.697s
+sys 0m1.131s
+
+3 runs with require_relative, booting 100 times each run:
+
+real  0m7.991s
+user  0m6.666s
+sys 0m1.118s
+
+real  0m8.020s
+user  0m6.686s
+sys 0m1.128s
+
+real  0m7.983s
+user  0m6.651s
+sys 0m1.121s
+
+ruby 2.0.0p247 (2013-06-27 revision 41674) [x86_64-darwin12.4.0]
+3 runs without require_relative, booting 100 times each run:
+
+real  0m7.241s
+user  0m6.159s
+sys 0m0.879s
+
+real  0m7.346s
+user  0m6.261s
+sys 0m0.901s
+
+real  0m7.218s
+user  0m6.157s
+sys 0m0.881s
+
+3 runs with require_relative, booting 100 times each run:
+
+real  0m7.224s
+user  0m6.165s
+sys 0m0.879s
+
+real  0m7.235s
+user  0m6.172s
+sys 0m0.882s
+
+real  0m7.253s
+user  0m6.193s
+sys 0m0.887s
+
+ruby 1.9.3p448 (2013-06-27 revision 41675) [x86_64-darwin12.4.0]
+3 runs without require_relative, booting 100 times each run:
+
+real  0m7.331s
+user  0m6.328s
+sys 0m0.831s
+
+real  0m7.026s
+user  0m6.073s
+sys 0m0.792s
+
+real  0m7.128s
+user  0m6.159s
+sys 0m0.811s
+
+3 runs with require_relative, booting 100 times each run:
+
+real  0m8.494s
+user  0m7.318s
+sys 0m0.962s
+
+real  0m7.074s
+user  0m6.116s
+sys 0m0.793s
+
+real  0m6.997s
+user  0m6.038s
+sys 0m0.791s
+
+ruby 1.9.2p320 (2012-04-20 revision 35421) [x86_64-darwin12.4.0]
+3 runs without require_relative, booting 100 times each run:
+
+real  0m9.484s
+user  0m6.893s
+sys 0m2.408s
+
+real  0m9.578s
+user  0m6.971s
+sys 0m2.435s
+
+real  0m9.451s
+user  0m6.890s
+sys 0m2.395s
+
+3 runs with require_relative, booting 100 times each run:
+
+real  0m9.480s
+user  0m6.917s
+sys 0m2.397s
+
+real  0m9.586s
+user  0m6.999s
+sys 0m2.418s
+
+real  0m9.523s
+user  0m6.949s
+sys 0m2.404s
+
+result_comment

lib/rspec/core.rb

@@ -1,4 +1,4 @@
-require_rspec = if defined?(require_relative)
+require_rspec = if ENV['REQUIRE_RELATIVE']
   lambda do |path|
     require_relative path
   end