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  1. #include <vector>
  2. #include <utility>
  3. #include <cstdio>
  4. #include <cstdint>
  5. #include <cstring>
  6. #include <ctime>
  7.  
  8. enum class ShapeType
  9. {
  10. 	rectangle = 0,
  11. 	circle = 1,
  12. 	triangle = 2,
  13. };
  14.  
  15. struct Shape
  16. {
  17. 	ShapeType type;
  18. 	virtual float getarea() = 0;
  19. };
  20.  
  21. struct Rectangle: Shape
  22. {
  23. 	float x;
  24. 	float y;
  25. 	virtual float getarea() override
  26. 	{
  27. 		return x * y;
  28. 	}
  29. };
  30.  
  31. struct Circle: Shape
  32. {
  33. 	float r;
  34. 	virtual float getarea() override
  35. 	{
  36. 		return 6.2831853072f * r;
  37. 	}
  38. };
  39.  
  40. struct Triangle: Shape
  41. {
  42. 	float a;
  43. 	float b;
  44. 	float cosp;
  45. 	virtual float getarea() override
  46. 	{
  47. 		return 0.5f * a * b * cosp;
  48. 	}
  49. };
  50.  
  51. union ShapeUnion
  52. {
  53. 	Rectangle rectangle;
  54. 	Circle circle;
  55. 	Triangle triangle;
  56.  
  57. 	ShapeUnion()
  58. 	{
  59. 	}
  60.  
  61. 	ShapeUnion( ShapeUnion&& other )
  62. 	{
  63. 		memcpy( this, &other, sizeof( ShapeUnion ) );
  64. 	}
  65.  
  66. 	~ShapeUnion()
  67. 	{
  68. 	}
  69.  
  70. 	float getarea_virtual();
  71. 	float getarea_switch();
  72. };
  73.  
  74. float ShapeUnion::getarea_virtual()
  75. {
  76.     Shape* ptr = ( Shape* )this;
  77. 	return ptr->getarea();
  78. }
  79.  
  80. float ShapeUnion::getarea_switch()
  81. {
  82. 	switch( ( ( Shape* )this )->type )
  83. 	{
  84. 		case ShapeType::rectangle:
  85. 			return rectangle.getarea();
  86. 		case ShapeType::circle:
  87. 			return circle.getarea();
  88. 		case ShapeType::triangle:
  89. 			return triangle.getarea();
  90. 	}
  91.     return 0;
  92. }
  93.  
  94. std::vector< ShapeUnion > suv;
  95.  
  96. void fill_vector()
  97. {
  98. 	suv.resize( 0x1000000 );
  99. 	for( auto& su: suv )
  100. 	{
  101. 		uint32_t n = uintptr_t( &su );
  102. 		n = ( n << 13 ) ^ n;
  103. 		n = n * ( n * n * 15731 + 789221 ) + 1376312589;
  104. 		switch( n % 3 )
  105. 		{
  106. 			case 0:
  107. 				new( &su )Rectangle();
  108. 				su.rectangle.type = ShapeType::rectangle;
  109. 				su.rectangle.x = n >> 16;
  110. 				su.rectangle.y = n & 0xffff;
  111. 			case 1:
  112. 				new( &su )Circle();
  113. 				su.circle.type = ShapeType::circle;
  114. 				su.circle.r = n;
  115. 			case 2:
  116. 				new( &su )Triangle();
  117. 				su.triangle.type = ShapeType::triangle;
  118. 				su.triangle.a = n >> 20;
  119. 				su.triangle.b = ( n >> 8 ) & 0xfff;
  120. 				su.triangle.cosp = ( n & 0xff ) / 255.0f;
  121. 		}
  122. 	}
  123. }
  124.  
  125. void test_virtual()
  126. {
  127. 	volatile float r;
  128. 	for( auto& su: suv )
  129. 	{
  130. 		r = su.getarea_virtual();
  131. 	}
  132.     ( void )r;
  133. }
  134.  
  135. void test_switch()
  136. {
  137. 	volatile float r;
  138. 	for( auto& su: suv )
  139. 	{
  140. 		r = su.getarea_switch();
  141. 	}
  142.     ( void )r;
  143. }
  144.  
  145. int main()
  146. {
  147. 	fill_vector();
  148. 	clock_t c1 = clock();
  149. 	for( int i = 0; i < 0x10; ++i )
  150. 	{
  151. 		test_virtual();
  152. 	}
  153. 	c1 = clock() - c1;
  154. 	clock_t c2 = clock();
  155. 	for( int i = 0; i < 0x10; ++i )
  156. 	{
  157. 		test_switch();
  158. 	}
  159. 	c2 = clock() - c2;
  160. 	printf( "%li\n%li\n", c1, c2 );
  161. 	return 0;
  162. }
  163.  
Success #stdin #stdout 4.55s 3456KB
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https://ideone.com/a52txX
language:
C++14 (gcc 8.3)
created:
7 years ago
visibility:
public

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