std::vector and std::list find_if and max_element performance

Question

I am confused about performance of my code tested for std::vector and std::list . Is there a difference between these two when it comes to find_if and max_element ?

Answer 1

In terms of big-O notation, both have identical performance of O(n). ( find_if can be less if the element is found sooner, but this is equally true for both containers.)

In terms of actual wall-clock time, the vector will perform better due to cache coherency; all the vector elements are sequential in memory, so accessing them will make better use of the CPU cache. A linked list's elements can be scattered throughout memory, and you also need to follow the list links which takes time.

Answer 2

Both algorithms are O(n) in terms of computational complexity, but vectors allocate their elements in a contiguous region of storage, which will most likely result in a higher cache hit rate. Traversing a lists, on the other hand, involves a scattered memory access pattern that is likelier to result in a higher rate of cache misses.

As always when it comes to performance, anyway, do measurements before making decisions.

Answer 3

For max_element, all elements of both list and array will be traversed. So, both are O(n) in terms of performance.

Again for find_if, the traversal will be linear (O(n)) for both the data structures.

I don't think there should not much of a difference apart from the constants relative to each.