Thread-safe lock-free array

Question

I have a C++ library, which supposed to do some computations on multiple threads. I made independent threads code (i.e. there are no shared variables between them), except f

Answer 1

This line

AtomicUInt64 ( std::atomic a ) : atomic ( atomic.load() ) {}

You're completely ignoring the argument you pass in, You probably want it to be a.load() and you probably want to take elements by const reference so they aren't copied.

AtomicUInt64 (const std::atomic& a) : atomic (a.load()) {}

As for what you're doing, I'm not sure if it is correct. The modification of the variables inside the array will be atomic, but if the vector is modified or reallocated (which is possible with push_back), then there's nothing to guarantee your array modifications will work between threads and be atomic.