Ensure to always run at least 1 iteration for both warmup and for mea…

…surement

* Fixes #120
* Using do-while loops to ensure the loops run at least once.

lib/benchmark/ips/job.rb

@@ -276,9 +276,7 @@ def run_warmup
           target = Timing.add_second before, @warmup / 2.0
 
           cycles = 1
-          warmup_iter = 1
-          warmup_time_us = 0.0
-          while Timing.now + warmup_time_us * 2 < target
+          begin
             t0 = Timing.now
             item.call_times cycles
             t1 = Timing.now
@@ -289,7 +287,7 @@ def run_warmup
             # then exit the loop to avoid overflows and start the 100ms warmup runs
             break if cycles >= POW_2_30
             cycles *= 2
-          end
+          end while Timing.now + warmup_time_us * 2 < target
 
           cycles = cycles_per_100ms warmup_time_us, warmup_iter
           @timing[item] = cycles
@@ -326,7 +324,8 @@ def run_benchmark
 
           target = Timing.add_second Timing.now, @time
 
-          while (before = Timing.now) < target
+          begin
+            before = Timing.now
             item.call_times cycles
             after = Timing.now
 
@@ -338,7 +337,7 @@ def run_benchmark
             iter += cycles
 
             measurements_us << iter_us
-          end
+          end while Timing.now < target
 
           final_time = before
 

test/test_benchmark_ips.rb

@@ -256,4 +256,36 @@ def test_hold!
     assert File.exist?(temp_file_name)
     File.unlink(temp_file_name)
   end
+
+  def test_small_warmup_and_time
+    report = Benchmark.ips do |x|
+      x.config(:warmup => 0.0000000001, :time => 0.001)
+      x.report("addition") { 1 + 2 }
+    end
+    assert_operator report.entries[0].iterations, :>=, 1
+
+    report = Benchmark.ips do |x|
+      x.config(:warmup => 0, :time => 0.0000000001)
+      x.report("addition") { 1 + 2 }
+    end
+    assert_equal 1, report.entries[0].iterations
+
+    report = Benchmark.ips do |x|
+      x.config(:warmup => 0.001, :time => 0.0000000001)
+      x.report("addition") { 1 + 2 }
+    end
+    assert_operator report.entries[0].iterations, :>=, 1
+
+    report = Benchmark.ips do |x|
+      x.config(:warmup => 0.0000000001, :time => 0.0000000001)
+      x.report("addition") { 1 + 2 }
+    end
+    assert_operator report.entries[0].iterations, :>=, 1
+
+    report = Benchmark.ips do |x|
+      x.config(:warmup => 0, :time => 0)
+      x.report("addition") { 1 + 2 }
+    end
+    assert_equal 1, report.entries[0].iterations
+  end
 end