Very simple question, what would be your way of storing 100 KB - 2 MB objects in memory? Object is made of 3 doubles and two strings (both mostly under 5 chars long). Would using struct instead of class be any better?
EDIT: I don't know why I said double, it is float .. :S
Any chance of using the Flyweight pattern ?
You can use a struct if your type represents a value type. Structs are cheaper to allocate and deallocate. Considering the design guidelines, you can use a struct if:
I doubt there is a difference between a struct and a class, certainly not in C++ where they are the essentially the same thing. 2M objects of the size you suggest is not that large on a modern Desktop system.
There are two main issues to consider when dealing with a large number of objects.
The first has been addressed in Frederik Gheysels' answer through the use of the Fly weight pattern, which is the memory issue.
The second issue is how to efficiently add and retrieve these objects/structs (depending which path you chose to follow). Obviously I am assuming you don't just create these objects and never want to retrieve them again ;)
To answer this question though, it really depends on how you want to add and access your data. From there you can decide which data structure is best suited for your task. For example maybe you want to process these objects in LIFO order, then a stack would be the most efficient way.
I don't know much about what you're doing but how about these rules of thumb?
If you're having to store the points in a Collection of some sort, then make them classes to save the overhead of boxing structs for storage.
If you're just using the points as input data to another object for processing, e.g. as points in a mesh for processing, then prefer an array to save the Collection class overheads.
If you're storing the points in an array then just make them structs as this is more efficient than making them classes.