堆2维数组，该版本是更快？ [英] 2-dimensional array on heap, which version is faster?

问题描述

double **array = new double* [X];
for (int i=0; i<X; i++)
    array[i] = new double [Y];

array[x][y] = n;

或

double *array = new double [X*Y];

array[x*Y+y] = n;

第二个版本创建速度更快，但访问是在第一个版本速度更快（使用卷积例如图像处理），不是吗？或者是可以忽略不计一切？

Second version is created faster, but access is in first version faster (e.g. image processing using convolution), isn't it? Or is it all negligible?

推荐答案

在理论上的第二个版本应该会更快，因为整个数组contiguouslly分配的，所以比第一它更多的缓存友好。

In theory the second version should be faster, because the entire array is allocated contiguouslly, so its more cache-friendly than the first.

但在实践中，个人资料，看看会发生什么。这样的性能问题，在很大程度上取决于你的体系结构，操作系统等。

But in practice, profile it and see what happens. This kind of performance questions depends heavily on your architecture, OS, etc.

在这里（除纹）我的建议是：考虑用标准容器（A 的std ::矢量＆lt;的std ::矢量＆lt; T＆GT;＆GT; 在这种情况下），这已经成型，测试，也使您的生活更轻松从原始指针和手动内存管理移动你而去。

My advise here (In addition to profiling) is: Consider to use standard containers (A std::vector<std::vector<T>> in this case) which had been profiled, tested, and also make your life easier moving you away from raw-pointers and manual memory management.

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