Data Access Patterns That Makes Your CPU Really Angry (opens in new tab)

Given an array of data, what is the slowest way to sum up the integers? Is it adding the numbers from left to right, adding them randomly, or doing something else? In this post, we are going to build a data access pattern from the ground up that sums numbers as slowly as possible by exploiting memory pitfalls. uint32_t* data = ...; // sequential data[0] + data[1] + data[2] + ... // random data[67] + data[69420] + data[42] + ... // the slowest data[A] + data[B] + data[C] + ... Spoiler: You can...