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  1. //
  2.  
  3. #include <chrono>
  4. #include <iostream>
  5. #include <vector>
  6. #include <tuple>
  7. #include <cassert>
  8. #include <cmath>
  9.  
  10. using namespace std;
  11. void benchmark();
  12. void benchmark_proper();
  13. int find_third_member_of_ptt(int z, int x);
  14.  
  15. int main()
  16. {
  17. 	benchmark();
  18. 	benchmark_proper();
  19.  
  20. }
  21.  
  22. ////////////////////////////////////////////////////////////////////////////////////////////////////
  23. //  Benchmark Code
  24. ////////////////////////////////////////////////////////////////////////////////////////////////////
  25.  
  26. class timer
  27. {
  28. private:
  29.     std::chrono::high_resolution_clock::time_point start_;
  30. public:
  31.     timer()
  32.     {
  33.         reset();
  34.     }
  35.     void reset()
  36.     {
  37.         start_ = std::chrono::high_resolution_clock::now();
  38.     }
  39.     std::chrono::milliseconds elapsed() const
  40.     {
  41.         return std::chrono::duration_cast<std::chrono::milliseconds>(
  42.             std::chrono::high_resolution_clock::now() - start_);
  43.     }
  44.     friend std::ostream &operator<<(std::ostream &sout, timer const &t)
  45.     {
  46.         return sout << t.elapsed().count() << "ms";
  47.     }
  48. };
  49. static constexpr int max_triples = 2000;
  50.  
  51. void benchmark()
  52. {
  53.     timer t;
  54.     t.reset();
  55. 	vector<tuple<int,int,int>> ptt;
  56.     for(int z = 1;; ++z)
  57.     {
  58.         for(int x = 1; x <= z; ++x)
  59.         {
  60.             for(int y = x; y <= z; ++y)
  61.             {
  62.                 if(x*x + y*y == z*z)
  63.                 {
  64.                     ptt.push_back(make_tuple(x,y,z));
  65.                     if(ptt.size() == max_triples)
  66.                         goto done;
  67.                 }
  68.             }
  69.         }
  70.     }
  71. done:
  72.     std::cout << t << '\n';
  73. 	//for (const auto & triplet :  ptt)
  74. 	//	cout << get<0>(triplet) << " " << get<1>(triplet) << " " << get <2>(triplet) << endl;
  75. }
  76. // -1 == not found, yes boost optional would be better choice
  77. int find_third_member_of_ptt(int z, int x)
  78. {
  79. 	assert(z>x);
  80. 	const int diff  = z*z - x*x; 
  81. 	const double sqroot = sqrt(diff);
  82. 	const int candidate1 = (int)sqroot;
  83. 	const int candidate2 = (int)sqroot +1;
  84. 	// next 2 checks are the same and should be in a function
  85. 	if ( (candidate1 >= x) && //prevents duplicates
  86. 		 (z*z == x*x + candidate1*candidate1))
  87. 		return candidate1;
  88. 	if ((candidate2 >= x) && //prevents duplicates
  89. 	     (z*z == x*x + candidate2*candidate2))
  90. 		return candidate2; 
  91. 	return -1;
  92. }
  93.  
  94. void benchmark_proper()
  95. {
  96.     timer t;
  97.     t.reset();
  98. 	vector<tuple<int,int,int>> ptt;
  99.     for(int z = 1;; ++z)
  100.     {
  101.         for(int x = 1; x < z; ++x)
  102.         {
  103. 				if (find_third_member_of_ptt(z,x) !=-1)
  104.                 {
  105. 					ptt.push_back(make_tuple(x,find_third_member_of_ptt(z,x),z)); // we are so fast we dont need to remember the rv of a function...
  106.                     if(ptt.size() == max_triples)
  107.                         goto done; // so great that we have goto in if now, goto == maintainable code, we could put it outside if but *I* know check only needs to be done if push_back occured 
  108. 				}
  109.         }
  110.     }
  111. done:
  112.     std::cout << t << '\n';
  113. 	//for (const auto & triplet :  ptt)
  114. 	//	cout << get<0>(triplet) << " " << get<1>(triplet) << " " << get <2>(triplet) << endl;
  115. }
  116.  
  117.  
Success #stdin #stdout 2.47s 3432KB
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2390ms
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https://ideone.com/ikmxwI
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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