C++核心准则Per.19:以可以预测的方式访问内存

Per.19: Access memory predictably

Per.19:以可以预测的方式访问内存

Reason（原因）

Performance is very sensitive to cache performance and cache algorithms favor simple (usually linear) access to adjacent data.

程序的性能和缓冲的性能直接相关，而缓冲算法更善于处理简单的（通常是线性的）访问连续数据。

Example（示例）

int matrix[rows][cols];

// bad
for (int c = 0; c < cols; ++c)
    for (int r = 0; r < rows; ++r)
        sum += matrix[r][c];

// good
for (int r = 0; r < rows; ++r)
    for (int c = 0; c < cols; ++c)
        sum += matrix[r][c];

原文链接

https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#per19-access-memory-predictably