chrono | Watches and reports on time series data | Time Series Database library

#include 
#include 
using namespace std;

class MyTimer {
 private:
  std::chrono::time_point starter;
  std::chrono::time_point ender;

 public:
  void startCounter() {
    starter = std::chrono::steady_clock::now();
  }

  double getCounter() {
    ender = std::chrono::steady_clock::now();
    return double(std::chrono::duration_cast(ender - starter).count()) /
           1000000;  // millisecond output
  }
  
  // timer need to have nanosecond precision
  int64_t getCounterNs() {
    return std::chrono::duration_cast(std::chrono::steady_clock::now() - starter).count();
  }
};

MyTimer timer1, timer2, timerMain;
volatile int64_t dummy = 0, res1 = 0, res2 = 0;

// time run without any time measure
void func0() {
    dummy++;
}

// we're trying to measure the cost of startCounter() and getCounterNs(), not "dummy++"
void func1() {
    timer1.startCounter();  
    dummy++;
    res1 += timer1.getCounterNs();
}

void func2() {
    // start your counter here
    dummy++;
    // res2 += end your counter here
}

int main()
{
    int i, ntest = 1000 * 1000 * 100;
    int64_t runtime0, runtime1, runtime2;

    timerMain.startCounter();
    for (i=1; i<=ntest; i++) func0();
    runtime0 = timerMain.getCounter();
    cout << "Time0 = " << runtime0 << "ms\n";

    timerMain.startCounter();
    for (i=1; i<=ntest; i++) func1();
    runtime1 = timerMain.getCounter();
    cout << "Time1 = " << runtime1 << "ms\n";

    timerMain.startCounter();
    for (i=1; i<=ntest; i++) func2();
    runtime2 = timerMain.getCounter();
    cout << "Time2 = " << runtime2 << "ms\n";

    return 0;
}

#include 
#include 
#include 
#include 
using namespace std;

const int p[9] =   {1, 10, 100, 
                    1000, 10000, 100000, 
                    1000000, 10000000, 100000000};
                    
class MyTimer {
 private:
  std::chrono::time_point starter;
  std::chrono::time_point ender;

 public:
  void startCounter() {
    starter = std::chrono::steady_clock::now();
  }

  double getCounter() {
    ender = std::chrono::steady_clock::now();
    return double(std::chrono::duration_cast(ender - starter).count()) /
           1000000;  // millisecond output
  }
};
                    
int convert1(char *a) {
    int res = 0;
    for (int i=0; i<9; i++) res = res * 10 + a[i] - 48;
    return res;
}

int convert2(char *a) {
    return (a[0] - 48) * p[8] + (a[1] - 48) * p[7] + (a[2] - 48) * p[6]
            + (a[3] - 48) * p[5] + (a[4] - 48) * p[4] + (a[5] - 48) * p[3]
            + (a[6] - 48) * p[2] + (a[7] - 48) * p[1] + (a[8] - 48) * p[0];
}

int convert3(char *a) {
    return (a[0] - 48) * p[8] + a[1] * p[7] + a[2] * p[6] + a[3] * p[5]
            + a[4] * p[4] + a[5] * p[3] + a[6] * p[2] + a[7] * p[1] + a[8]
            - 533333328;
}

const unsigned pu[9] = {1, 10, 100, 1000, 10000, 100000, 1000000, 10000000,
    100000000};

int convert4u(char *aa) {
  const unsigned char *a = (const unsigned char*) aa;
  return a[0] * pu[8] + a[1] * pu[7] + a[2] * pu[6] + a[3] * pu[5] + a[4] * pu[4]
      + a[5] * pu[3] + a[6] * pu[2] + a[7] * pu[1] + a[8] - (unsigned) 5333333328u;
}

int convert5(char* a) {
    int val = 0;
    for(size_t k =0;k <9;++k) {
        val = (val << 3) + (val << 1) + (a[k]-'0');
    }
    return val;
}

const unsigned pu2[9] = {100000000, 10000000, 1000000, 100000, 10000, 1000, 100, 10, 1};

int convert6u(char *a) {
  return a[0]*pu2[0] + a[1]*pu2[1] + a[2]*pu2[2] + a[3] * pu2[3] + a[4] * pu2[4] + a[5] * pu2[5] + a[6] * pu2[6] + a[7] * pu2[7] + a[8] - (unsigned) 5333333328u;
}

using ConvertFunc = int(char*);    

volatile int result = 0; // do something with the result of function to prevent unexpected optimization
void benchmark(ConvertFunc converter, string name, int numTest=10000) {
    MyTimer timer;
    const int N = 100000;
    char *a = new char[9*N + 1];
    double runtime = 0;
    
    for (int t=1; t<=numTest; t++) {        
        // change something to prevent unexpected optimization
        for (int i=0; i<9*N; i++) a[i] = rand() % 10 + '0'; 

        timer.startCounter();
        for (int i=0; i<9*N; i+= 9) result = converter(a+i);
        runtime += timer.getCounter();
    }
    cout << name << ": " << runtime << "ms\n";
}   

int main() {        
    benchmark(convert1, "slow");
    benchmark(convert2, "normal");    
    benchmark(convert3, "fast");
    benchmark(convert4u, "unsigned");
    benchmark(convert5, "shifting");
    benchmark(convert6u, "reverse");
    return 0;
}