c++ - calloc/malloc 比 C++ 中的 operator new 快吗

Question

我想知道的是，如果我在 C++ 程序中使用 calloc/malloc 而不是 operator new，它会使内存分配更快，还是因为使用 C++ 编译器来编译程序，这无关紧要。

编辑:

我想很明显我没有使用 new 运算符来调用构造函数。只是像数组一样的内存分配。

Answer 1

对于我测试过的大多数编译器，当您使用 new 时执行的额外初始化意味着它比 malloc 慢分钟(在至少在处理两者至少具有模糊可比性的简单类型时)。例如:

Test Name:   D000001                         Class Name:  Allocation
CPU Time:        56.8  nanoseconds           plus or minus       2.84
Wall/CPU:        1.02  ratio.                Iteration Count:  419430400
Test Description:
 Dynamic array allocation, use and deallocation time measurement
 Dynamic array of 1000 integers
 get space on heap using malloc() and use it in a procedure on each call



Test Name:   D000002                         Class Name:  Allocation
CPU Time:         238  nanoseconds           plus or minus       11.9
Wall/CPU:        1.03  ratio.                Iteration Count:  104857600
Test Description:
 Dynamic array allocation, initialization, use and deallocation time measurement

 Dynamic array of 1000 integers
 get space on heap using malloc() and use it in a procedure on each call



Test Name:   D000003                         Class Name:  Allocation
CPU Time:        60.4  nanoseconds           plus or minus       3.02
Wall/CPU:        1.02  ratio.                Iteration Count:  419430400
Test Description:
 Dynamic array allocation, use and deallocation time measurement
 Dynamic array of 1000 integers
 get space on heap using NEW and use it in a procedure on each call



Test Name:   D000004                         Class Name:  Allocation
CPU Time:         249  nanoseconds           plus or minus       12.4
Wall/CPU:        1.03  ratio.                Iteration Count:  104857600
Test Description:
 Dynamic array allocation, initialization, use and deallocation time measurement

 Dynamic array of 1000 integers
 get space on heap using NEW and use it in a procedure on each call

因此，malloc 的平均速度更快，但在速度上有足够的差异(在 new 和 malloc 中)，单个调用new 实际上可能比单独调用 malloc 更快。​​