Vector storage in C++

Question

I wish to store a large vector of d-dimensional points (d fixed and small: <10).

If I define a Point as vector, I think a v

Answer 1

If you define your Point as having contiguous data storage (e.g. struct Point { int a; int b; int c; } or using std::array), then std::vector will store the Points in contiguous memory locations, so your memory layout will be:

p0.a, p0.b, p0.c, p1.a, p1.b, p1.c, ..., p(N-1).a, p(N-1).b, p(N-1).c

On the other hand, if you define Point as a vector, then a vector has the layout of vector>, which is not contiguous, as vector stores pointers to dynamically allocated memory. So you have contiguity for single Points, but not for the whole structure.

The first solution is much more efficient than the second (as modern CPUs love accessing contiguous memory locations).