I have this minimal example of Google Benchmark usage. The weird thing is that "42" is printed a number of times (4), not just once. I understand that the library has to run things several times to gain statistics but this I though that this is handled by the statie-loop itself.
This is a minimal example of something more complicated where I wanted to print (outside the loop) the result to verify that different implementations of the same function would give the same result.
#include <benchmark/benchmark.h>
#include<iostream>
#include <thread> //sleep for
int SomeFunction(){
using namespace std::chrono_literals;
std::this_thread::sleep_for(10ms);
return 42;
}
static void BM_SomeFunction(benchmark::State& state) {
// Perform setup here
int result = -1;
for (auto _ : state) {
// This code gets timed
result = SomeFunction();
benchmark::DoNotOptimize(result);
}
std::cout<< result <<std::endl;
}
// Register the function as a benchmark
BENCHMARK(BM_SomeFunction);
// Run the benchmark
BENCHMARK_MAIN();
output: (42 is printed 4 times, why more than once, why 4?)
Running ./a.out
Run on (12 X 4600 MHz CPU s)
CPU Caches:
L1 Data 32 KiB (x6)
L1 Instruction 32 KiB (x6)
L2 Unified 256 KiB (x6)
L3 Unified 12288 KiB (x1)
Load Average: 0.30, 0.65, 0.79
42
42
42
42
----------------------------------------------------------
Benchmark Time CPU Iterations
----------------------------------------------------------
BM_SomeFunction 10243011 ns 11051 ns 1000
How else could I test (at least visually) that different benchmarking blocks give the same answer?
