complexity_test: do more stuff in empty loop

google · Feb 17, 2024 · bd48182 · bd48182
1 parent e703685
commit bd48182
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Showing 2 changed files with 33 additions and 15 deletions.
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
@@ -218,14 +218,8 @@ if(NOT (MSVC OR CMAKE_CXX_SIMULATE_ID STREQUAL "MSVC"))
   benchmark_add_test(NAME cxx03 COMMAND cxx03_test --benchmark_min_time=0.01s)
 endif()
 
-# Attempt to work around flaky test failures when running on Appveyor servers.
-if (DEFINED ENV{APPVEYOR})
-  set(COMPLEXITY_MIN_TIME "0.5s")
-else()
-  set(COMPLEXITY_MIN_TIME "0.01s")
-endif()
 compile_output_test(complexity_test)
-benchmark_add_test(NAME complexity_benchmark COMMAND complexity_test --benchmark_min_time=${COMPLEXITY_MIN_TIME})
+benchmark_add_test(NAME complexity_benchmark COMMAND complexity_test --benchmark_min_time=1000000x)
 
 ###############################################################################
 # GoogleTest Unit Tests

diff --git a/test/complexity_test.cc b/test/complexity_test.cc
@@ -70,8 +70,14 @@ int AddComplexityTest(const std::string &test_name,
 void BM_Complexity_O1(benchmark::State &state) {
   for (auto _ : state) {
     // This test requires a non-zero CPU time to avoid divide-by-zero
-    auto iterations = double(state.iterations()) * double(state.iterations());
-    benchmark::DoNotOptimize(iterations);
+    benchmark::DoNotOptimize(state.iterations());
+    double tmp = state.iterations();
+    benchmark::DoNotOptimize(tmp);
+    for (benchmark::IterationCount i = 0; i < state.iterations(); ++i) {
+      benchmark::DoNotOptimize(state.iterations());
+      tmp *= state.iterations();
+      benchmark::DoNotOptimize(tmp);
+    }
 
     // always 1ns per iteration
     state.SetIterationTime(42 * 1e-9);
@@ -113,8 +119,14 @@ ADD_COMPLEXITY_CASES(one_test_name, big_o_1_test_name, rms_o_1_test_name,
 void BM_Complexity_O_N(benchmark::State &state) {
   for (auto _ : state) {
     // This test requires a non-zero CPU time to avoid divide-by-zero
-    auto iterations = double(state.iterations()) * double(state.iterations());
-    benchmark::DoNotOptimize(iterations);
+    benchmark::DoNotOptimize(state.iterations());
+    double tmp = state.iterations();
+    benchmark::DoNotOptimize(tmp);
+    for (benchmark::IterationCount i = 0; i < state.iterations(); ++i) {
+      benchmark::DoNotOptimize(state.iterations());
+      tmp *= state.iterations();
+      benchmark::DoNotOptimize(tmp);
+    }
 
     // 1ns per iteration per entry
     state.SetIterationTime(state.range(0) * 42 * 1e-9);
@@ -165,8 +177,14 @@ static const double kLog2E = 1.44269504088896340736;
 static void BM_Complexity_O_N_log_N(benchmark::State &state) {
   for (auto _ : state) {
     // This test requires a non-zero CPU time to avoid divide-by-zero
-    auto iterations = double(state.iterations()) * double(state.iterations());
-    benchmark::DoNotOptimize(iterations);
+    benchmark::DoNotOptimize(state.iterations());
+    double tmp = state.iterations();
+    benchmark::DoNotOptimize(tmp);
+    for (benchmark::IterationCount i = 0; i < state.iterations(); ++i) {
+      benchmark::DoNotOptimize(state.iterations());
+      tmp *= state.iterations();
+      benchmark::DoNotOptimize(tmp);
+    }
 
     state.SetIterationTime(state.range(0) * kLog2E * std::log(state.range(0)) *
                            42 * 1e-9);
@@ -219,8 +237,14 @@ ADD_COMPLEXITY_CASES(n_lg_n_test_name, big_o_n_lg_n_test_name,
 void BM_ComplexityCaptureArgs(benchmark::State &state, int n) {
   for (auto _ : state) {
     // This test requires a non-zero CPU time to avoid divide-by-zero
-    auto iterations = double(state.iterations()) * double(state.iterations());
-    benchmark::DoNotOptimize(iterations);
+    benchmark::DoNotOptimize(state.iterations());
+    double tmp = state.iterations();
+    benchmark::DoNotOptimize(tmp);
+    for (benchmark::IterationCount i = 0; i < state.iterations(); ++i) {
+      benchmark::DoNotOptimize(state.iterations());
+      tmp *= state.iterations();
+      benchmark::DoNotOptimize(tmp);
+    }
 
     state.SetIterationTime(state.range(0) * 42 * 1e-9);
   }