Added test file and Complexity() interface

include/benchmark/benchmark_api.h

@@ -231,6 +231,20 @@ enum TimeUnit {
   kMillisecond
 };
 
+// BigO is passed to a benchmark in order to specify the asymptotic computational 
+// complexity for the benchmark.
+enum BigO {
+  O_None,
+  O_1,
+  O_N,
+  O_M_plus_N,
+  O_N_Squared,
+  O_N_Cubed,
+  O_log_N,
+  O_N_log_N,
+  O_Auto
+};
+
 // State is passed to a running Benchmark and contains state for the
 // benchmark to use.
 class State {
@@ -465,6 +479,10 @@ public:
   // to control how many iterations are run, and in the printing of items/second
   // or MB/second values.
   Benchmark* UseManualTime();
+  
+  // Set the asymptotic computational complexity for the benchmark. This option
+  // called the asymptotic computational complexity will be shown on the output. 
+  Benchmark* Complexity(BigO complexity);
 
   // Support for running multiple copies of the same benchmark concurrently
   // in multiple threads.  This may be useful when measuring the scaling

src/benchmark.cc

@@ -290,6 +290,7 @@ struct Benchmark::Instance {
   int            range_multiplier;
   bool           use_real_time;
   bool           use_manual_time;
+  BigO           complexity;
   double         min_time;
   int            threads;    // Number of concurrent threads to use
   bool           multithreaded;  // Is benchmark multi-threaded?
@@ -331,6 +332,7 @@ public:
   void MinTime(double n);
   void UseRealTime();
   void UseManualTime();
+  void Complexity(BigO complexity);
   void Threads(int t);
   void ThreadRange(int min_threads, int max_threads);
   void ThreadPerCpu();
@@ -349,6 +351,7 @@ private:
   double min_time_;
   bool use_real_time_;
   bool use_manual_time_;
+  BigO complexity_;
   std::vector<int> thread_counts_;
 
   BenchmarkImp& operator=(BenchmarkImp const&);
@@ -411,6 +414,7 @@ bool BenchmarkFamilies::FindBenchmarks(
         instance.min_time = family->min_time_;
         instance.use_real_time = family->use_real_time_;
         instance.use_manual_time = family->use_manual_time_;
+        instance.complexity = family->complexity_;
         instance.threads = num_threads;
         instance.multithreaded = !(family->thread_counts_.empty());
 
@@ -447,7 +451,8 @@ bool BenchmarkFamilies::FindBenchmarks(
 BenchmarkImp::BenchmarkImp(const char* name)
     : name_(name), arg_count_(-1), time_unit_(kNanosecond),
       range_multiplier_(kRangeMultiplier), min_time_(0.0), 
-      use_real_time_(false), use_manual_time_(false) {
+      use_real_time_(false), use_manual_time_(false),
+      complexity_(O_None) {
 }
 
 BenchmarkImp::~BenchmarkImp() {
@@ -523,6 +528,10 @@ void BenchmarkImp::UseManualTime() {
   use_manual_time_ = true;
 }
 
+void BenchmarkImp::Complexity(BigO complexity){
+  complexity_ = complexity;
+}
+
 void BenchmarkImp::Threads(int t) {
   CHECK_GT(t, 0);
   thread_counts_.push_back(t);
@@ -636,6 +645,11 @@ Benchmark* Benchmark::UseManualTime() {
   return this;
 }
 
+Benchmark* Benchmark::Complexity(BigO complexity) {
+  imp_->Complexity(complexity);
+  return this;
+}
+
 Benchmark* Benchmark::Threads(int t) {
   imp_->Threads(t);
   return this;

test/CMakeLists.txt

@@ -47,6 +47,9 @@ set_target_properties(cxx03_test
     PROPERTIES COMPILE_FLAGS "${CXX03_FLAGS}")
 add_test(cxx03 cxx03_test --benchmark_min_time=0.01)
 
+compile_benchmark_test(complexity_test)
+add_test(complexity_benchmark complexity_test --benchmark_min_time=0.01)
+
 # Add the coverage command(s)
 if(CMAKE_BUILD_TYPE)
   string(TOLOWER ${CMAKE_BUILD_TYPE} CMAKE_BUILD_TYPE_LOWER)
@@ -66,7 +69,7 @@ if (${CMAKE_BUILD_TYPE_LOWER} MATCHES "coverage")
       COMMAND ${LCOV} -q -a before.lcov -a after.lcov --output-file final.lcov
       COMMAND ${LCOV} -q -r final.lcov "'${CMAKE_SOURCE_DIR}/test/*'" -o final.lcov
       COMMAND ${GENHTML} final.lcov -o lcov --demangle-cpp --sort -p "${CMAKE_BINARY_DIR}" -t benchmark
-      DEPENDS filter_test benchmark_test options_test basic_test fixture_test cxx03_test
+      DEPENDS filter_test benchmark_test options_test basic_test fixture_test cxx03_test complexity_test
       WORKING_DIRECTORY ${CMAKE_BINARY_DIR}
       COMMENT "Running LCOV"
     )

test/complexity_test.cc

@@ -0,0 +1,107 @@
+
+#include "benchmark/benchmark_api.h"
+
+#include <string>
+#include <vector>
+#include <map>
+#include <algorithm>
+
+std::vector<int> ConstructRandomVector(int size) {
+  std::vector<int> v;
+  v.reserve(size);
+  for (int i = 0; i < size; ++i) {
+    v.push_back(rand() % size);
+  }
+  return v;
+}
+
+std::map<int, int> ConstructRandomMap(int size) {
+  std::map<int, int> m;
+  for (int i = 0; i < size; ++i) {
+    m.insert(std::make_pair(rand() % size, rand() % size));
+  }
+  return m;
+}
+
+void BM_Complexity_O1(benchmark::State& state) {
+  while (state.KeepRunning()) {
+  }
+}
+BENCHMARK(BM_Complexity_O1) -> Range(1, 1<<17) -> Complexity(benchmark::O_1);
+
+static void BM_Complexity_O_N(benchmark::State& state) {
+  auto v = ConstructRandomVector(state.range_x());
+  const int itemNotInVector = state.range_x()*2; // Test worst case scenario (item not in vector)
+  while (state.KeepRunning()) {
+      benchmark::DoNotOptimize(std::find(v.begin(), v.end(), itemNotInVector));
+  }
+}
+BENCHMARK(BM_Complexity_O_N) -> Range(1, 1<<10) -> Complexity(benchmark::O_N);
+BENCHMARK(BM_Complexity_O_N) -> Range(1, 1<<10) -> Complexity(benchmark::O_Auto);
+
+static void BM_Complexity_O_M_plus_N(benchmark::State& state) {
+  std::string s1(state.range_x(), '-');
+  std::string s2(state.range_x(), '-');
+  while (state.KeepRunning())
+    benchmark::DoNotOptimize(s1.compare(s2));
+}
+BENCHMARK(BM_Complexity_O_M_plus_N)
+	->RangeMultiplier(2)->Range(1<<10, 1<<18) -> Complexity(benchmark::O_M_plus_N);
+    
+static void BM_Complexity_O_N_Squared(benchmark::State& state) {
+  std::string s1(state.range_x(), '-');
+  std::string s2(state.range_x(), '-');
+  while (state.KeepRunning())
+    for(char& c1 : s1) {
+        for(char& c2 : s2) {
+            benchmark::DoNotOptimize(c1 = 'a');
+            benchmark::DoNotOptimize(c2 = 'b');
+        }
+    }
+}
+BENCHMARK(BM_Complexity_O_N_Squared) -> Range(1, 1<<8) -> Complexity(benchmark::O_N_Squared);
+    
+static void BM_Complexity_O_N_Cubed(benchmark::State& state) {
+  std::string s1(state.range_x(), '-');
+  std::string s2(state.range_x(), '-');
+  std::string s3(state.range_x(), '-');
+  while (state.KeepRunning())
+    for(char& c1 : s1) {
+        for(char& c2 : s2) {
+            for(char& c3 : s3) {
+                benchmark::DoNotOptimize(c1 = 'a');
+                benchmark::DoNotOptimize(c2 = 'b');
+                benchmark::DoNotOptimize(c3 = 'c');
+            }
+        }
+    }
+}
+BENCHMARK(BM_Complexity_O_N_Cubed) -> DenseRange(1, 8) -> Complexity(benchmark::O_N_Cubed);
+
+static void BM_Complexity_O_log_N(benchmark::State& state) {
+  auto m = ConstructRandomMap(state.range_x());
+  const int itemNotInVector = state.range_x()*2; // Test worst case scenario (item not in vector)
+  while (state.KeepRunning()) {
+      benchmark::DoNotOptimize(m.find(itemNotInVector));
+  }
+}
+BENCHMARK(BM_Complexity_O_log_N) -> Range(1, 1<<10) -> Complexity(benchmark::O_log_N);
+
+static void BM_Complexity_O_N_log_N(benchmark::State& state) {
+  auto v = ConstructRandomVector(state.range_x());
+  while (state.KeepRunning()) {
+      std::sort(v.begin(), v.end());
+  }
+}
+BENCHMARK(BM_Complexity_O_N_log_N) -> Range(1, 1<<16) -> Complexity(benchmark::O_N_log_N);
+BENCHMARK(BM_Complexity_O_N_log_N) -> Range(1, 1<<16) -> Complexity(benchmark::O_Auto);
+
+// Test benchmark with no range. Complexity is always calculated as O(1).
+void BM_Extreme_Cases(benchmark::State& state) {
+  while (state.KeepRunning()) {
+  }
+}
+BENCHMARK(BM_Extreme_Cases);
+BENCHMARK(BM_Extreme_Cases)->Arg(42);
+
+BENCHMARK_MAIN()