Timer.cpp

/** Log execution time of a block of code in nanoseconds and milliseconds 
 * Just add a Timer object at the start of the code block.
 * Provide a prefix string about some context
 *
 * Example:
 * long LargestPrimeFactor(const long num)
 * {
 *  Timer t("LargestPrimeFactor:(" + std::to_string(num) + ") ");
 *	//stuff here..
 * }
 *
 * Output:
 * LargestPrimeFactor:(13195) 718315 ns 0ms
 */

#include <iostream>
#include <chrono>
#include <string>

class Timer {
public:
 Timer(const std::string &pre) :
 start(std::chrono::high_resolution_clock::now()),
 prefix(pre)
 {}
 
 ~Timer()
 {
  std::chrono::time_point<std::chrono::high_resolution_clock> end = std::chrono::high_resolution_clock::now();
  std::chrono::nanoseconds dt = end - start;
  std::cout << prefix << dt.count() << " ns "
  			<< std::chrono::duration_cast<std::chrono::milliseconds>(dt).count() << "ms"
  			<< std::endl;
 }
 
private:
 std::chrono::time_point<std::chrono::high_resolution_clock> start;
 std::string prefix;
};