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  1. #include <iostream>
  2. #include <ctime>
  3. #include <cstdlib>
  4.  
  5. using namespace std;
  6.  
  7. #define N 500
  8.  
  9. void mult1(int **a, int **b, int **c)
  10. {
  11. 	for (unsigned q=0; q<N; ++q)
  12. 		for (unsigned w=0; w<N; ++w)
  13. 			c[q][w] = 0;
  14.  
  15. 	for (unsigned q=0; q<N; ++q)
  16. 		for (unsigned w=0; w<N; ++w)
  17. 			for (unsigned e=0; e<N; ++e)
  18. 				c[q][w] += a[q][e] * b[e][w];
  19. }
  20.  
  21. void mult2(int **a, int **b, int **c)
  22. {
  23. 	for (unsigned q=0; q<N; ++q)
  24. 		for (unsigned w=0; w<N; ++w)
  25. 			c[q][w] = 0;
  26.  
  27. 	for (unsigned q=0; q<N; ++q)
  28. 		for (unsigned w=0; w<N; ++w)
  29. 			for (unsigned e=0; e<N; ++e)
  30. 				c[q][w] += a[q][e] * b[w][e];
  31. }
  32.  
  33. int main()
  34. {
  35. 	int **a = new int*[N];
  36. 	int **b = new int*[N];
  37. 	int **c = new int*[N];
  38.  
  39. 	for (unsigned q=0; q<N; ++q)
  40. 	{
  41. 		a[q] = new int[N];
  42. 		b[q] = new int[N];
  43. 		c[q] = new int[N];
  44.  
  45. 		for (unsigned w=0; w<N; ++w)
  46. 		{
  47. 			a[q][w] = rand();
  48. 			b[q][w] = rand();
  49. 		}
  50. 	}
  51.  
  52. 	long m1=0, m2=0;
  53.  
  54. 	for (unsigned q=0; q<10; ++q)
  55. 	{
  56. 		long t = clock();
  57. 		mult1(a, b, c);
  58. 		m1 += t = clock() - t;
  59. 		cout << "1: " << t << endl;
  60.  
  61. 		t = clock();
  62. 		mult2(a, b, c);
  63. 		m2 += t = clock() - t;
  64. 		cout << "2: " << t << endl;
  65. 	}
  66.  
  67. 	cout << endl << "Results: " << m1 << ", " << m2 << endl;
  68.  
  69. 	return 0;
  70. }
Success #stdin #stdout 1.86s 6372KB
comments (?)
stdin 
Standard input is empty
stdout 
1: 107045
2: 78591
1: 106390
2: 78578
1: 106600
2: 78721
1: 106352
2: 78212
1: 106978
2: 78166
1: 106401
2: 78655
1: 106400
2: 77978
1: 106432
2: 78071
1: 106269
2: 78073
1: 106523
2: 77941

Results: 1065390, 782986
https://ideone.com/Uposm6
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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