Add benchmark for Bignum#to_s

benchmark/core/bignum/bench_to_s.rb

@@ -0,0 +1,44 @@
+require 'benchmark'
+require 'benchmark/ips'
+require 'benchmark/helpers'
+
+Benchmark.ips do |x|
+
+  small_bignum  = Benchmark::Helpers.fixnum_max + 1
+  medium_bignum = Benchmark::Helpers.fixnum_max ** 10
+  large_bignum  = Benchmark::Helpers.fixnum_max ** 100
+  huge_bignum   = Benchmark::Helpers.fixnum_max ** 1000
+
+  x.report "small Bignum#to_s" do |times|
+    i = 0
+    while i < times
+      small_bignum.to_s
+      i += 1
+    end
+  end
+
+  x.report "medium Bignum#to_s" do |times|
+    i = 0
+    while i < times
+      medium_bignum.to_s
+      i += 1
+    end
+  end
+
+  x.report "large Bignum#to_s" do |times|
+    i = 0
+    while i < times
+      large_bignum.to_s
+      i += 1
+    end
+  end
+
+  x.report "huge Bignum#to_s" do |times|
+    i = 0
+    while i < times
+      huge_bignum.to_s
+      i += 1
+    end
+  end
+
+end