cout vs fmt::print

test.cpp

#define FMT_HEADER_ONLY 
#include <cassert>
#include <iostream>
#include "fmt/core.h"
#include <Windows.h>

void useCout() {
  for (unsigned i = 0; i < 4000; i++) {
    std::cout << "cupcakes are made of flour, eggs, and sugar";
  }
  std::cout.flush();
}

void useFMT() {
  for (unsigned i = 0; i < 4000; i++) {
    fmt::print("cupcakes are made of flour, eggs, and sugar");
  }
}

static inline int64_t GetTicks()
{
  LARGE_INTEGER ticks;
  bool res = QueryPerformanceCounter(&ticks);
  assert(res);
  return ticks.QuadPart;
}

int main()
{
  constexpr std::size_t size = 1024 * 8;
  char buffer[size];
  std::cout.rdbuf()->pubsetbuf(buffer, size);
  std::ios::sync_with_stdio(false);

  const auto tick0 = GetTicks();
  useCout();
  const auto tick1 = GetTicks();
  useFMT(); 
  const auto tick2 = GetTicks();
  
  std::cout << "\n\ntime cout = " << tick1 - tick0
    << "\ntime fmt  = " << tick2 - tick1
    << std::endl;
}