侯捷STL学习(三)--分配器测试

第七节：分配器测试

• 标准的分配器Allocator,#include<ext/...>都是拓展的
• 可以用不同的分配器测试同一容器
• 分配器allocate() & deallocate()进行内存的分配和释放，这样操作太麻烦了
• 实际用到得new delete malloc free释放时并没有指定分配产生的字节
• 关于分配器实现需要后续的源码分析

• 测试

#include <list>
#include <stdexcept>
#include <string>
#include <cstdlib> 		//abort()
#include <cstdio>  		//snprintf()
#include <algorithm> 	//find()
#include <iostream>
#include <ctime> 

#include <cstddef>
#include <memory>	//內含 std::allocator
	//欲使用 std::allocator 以外的 allocator, 得自行 #include <ext\...>
#ifdef __GNUC__
#include <ext\array_allocator.h>
#include <ext\mt_allocator.h>
#include <ext\debug_allocator.h>
#include <ext\pool_allocator.h>
#include <ext\bitmap_allocator.h>
#include <ext\malloc_allocator.h>
#include <ext\new_allocator.h>
#endif

namespace jj20
{
//pass A object to function template impl()，
//而 A 本身是個 class template, 帶有 type parameter T,
//那麼有無可能在 impl() 中抓出 T, 創建一個 list<T, A<T>> object?
//以下先暫時迴避上述疑問.

void test_list_with_special_allocator()
{
#ifdef __GNUC__
	cout << "\ntest_list_with_special_allocator().......... \n";

    //不能在 switch case 中宣告，只好下面這樣. 				//1000000次
    list<string, allocator<string>> c1;						//3140
	list<string, __gnu_cxx::malloc_allocator<string>> c2;  	//3110
    list<string, __gnu_cxx::new_allocator<string>> c3; 		//3156
	list<string, __gnu_cxx::__pool_alloc<string>> c4;  		//4922
	list<string, __gnu_cxx::__mt_alloc<string>> c5; 		//3297
    list<string, __gnu_cxx::bitmap_allocator<string>> c6;  	//4781 														

int choice;
long value;     

	cout << "select: "
		 << " (1) std::allocator "
	     << " (2) malloc_allocator "
	     << " (3) new_allocator "
	     << " (4) __pool_alloc "
	     << " (5) __mt_alloc "
		 << " (6) bitmap_allocator ";

	cin >> choice;
	if ( choice != 0 ) {
		cout << "how many elements: ";
		cin >> value;
	}

char buf[10];
clock_t timeStart = clock();
    for(long i=0; i< value; ++i)
    {
    	try {
    		snprintf(buf, 10, "%d", i);
	        switch (choice)
	        {
	 	        case 1 : 	c1.push_back(string(buf));
		 					break;
		        case 2 : 	c2.push_back(string(buf));
		 					break;
		        case 3 : 	c3.push_back(string(buf));
		 					break;
		        case 4 : 	c4.push_back(string(buf));
		 					break;
		        case 5 : 	c5.push_back(string(buf));
		 					break;
		        case 6 : 	c6.push_back(string(buf));
		 					break;
		        default:
		 			break;
	        }
		}
		catch(exception& p) {
			cout << "i=" << i << " " << p.what() << endl;
			abort();
		}
	}
	cout << "a lot of push_back(), milli-seconds : " << (clock()-timeStart) << endl;	

	//test all allocators' allocate() & deallocate();
	int* p;
    allocator<int> alloc1;
	p = alloc1.allocate(1);
	alloc1.deallocate(p,1); 	

	__gnu_cxx::malloc_allocator<int> alloc2;
	p = alloc2.allocate(1);
	alloc2.deallocate(p,1);  	

    __gnu_cxx::new_allocator<int> alloc3;
	p = alloc3.allocate(1);
	alloc3.deallocate(p,1); 	

	__gnu_cxx::__pool_alloc<int> alloc4;
	p = alloc4.allocate(2);
	alloc4.deallocate(p,2); 	//我刻意令參數為 2, 但這有何意義!! 一次要 2 個 ints? 

	__gnu_cxx::__mt_alloc<int> alloc5;
	p = alloc5.allocate(1);
	alloc5.deallocate(p,1);  	

    __gnu_cxx::bitmap_allocator<int> alloc6;
	p = alloc6.allocate(3);
	alloc6.deallocate(p,3);  	//我刻意令參數為 3, 但這有何意義!! 一次要 3 個 ints?
#endif
}
}