What to do without generating instances with "new" [closed] - c++

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In some video games, I find that everytime a new character is created a factory method is used create the new one like this
class CharacterEngine
{
public:
static Character* CreateCharacter(string Name, Weapons InitialWeapons)
{
return new Character(Name, InitialWeapons);
}
};
//...
Now that if I have 100000000 characters (very many, e.g like simulated particles), heap allocation like this may fail to work on computers with small RAM. What is your solution to this problem?
Edit
What other methods or designs do you know can change or replace the factory method/class?

Answer 1

Do you actually have 100K characters? And are you actually in an environment in which you are memory constrained and allocation fails? Even if Character is a whopping 1KB in side, you'd be looking at 100MBs consumed, which isn't that much, even for feature phones.
But perhaps you're worried that you might actually have memory to spare, but fragmentation is so high you can't use it. That's a fairer concern, and one usually relevant to games. Perhaps take a look at the object pool pattern. Also, taking into consideration the large number of characters you're speaking of, perhaps flighweight might also help!
Finally, running out of memory isn't like other program errors like losing a TCP connection or facing a disk error. If you need to allocate the 100001th character and there's no more memory for it you can't not allocate it, show an error to the user or try again later. You can't go on without them as it were. So don't - just bail the program and perhaps do whatever cleaning up is required to not lose too much game state etc. Have a read for malloc never fails as well.

Answer 2

The heap memory is obviously limited, but the limit is in practice not that small (at least gigabytes on current PCs).
And memory consumption is not the biggest problem in a game. If you have many characters, you might need to deal with interactions between them, and that could be more difficult (e.g. determining the set of characters close to a given one could be more challenging).
You should read more about memory management, virtual address space, smart pointers, reference counting, RAII, circular references, weak references, hash consing.
Notice that the heap is global to your program & process (it is not the property of some particular class or code chunk, but of your entire program).
The heap allocation routines (related to new & delete) are generally implemented about some operating system primitives (often system calls) to grow the virtual address space. On Linux, see mmap(2). The operating system could provide some mean to query your virtual address space (on Linux, see proc(5) and for a process of pid 1234, the /proc/1234/maps pseudo-file).
I recommend reading a good book on garbage collection, such as the GC handbook. It teaches you concepts and terminology which are relevant for C++ programming (notably in games). In some sense, you may want to implement your own GC for your game.
C++ has some allocator concept and standard containers know about that.
Read also some Introduction to Algorithms.
heap allocation like this may fail to work on computers with small RAM.
Then either improve your program to use less memory, or get a bigger computer. Perhaps consider some distributed computing approach (e.g. cloud computing), like in MMORG.
What other methods or designs do you know can change or replace the factory method/class?
They won't change much the consumed memory, because in your design every character is represented by its unique C++ object. So that does not matter much.

Answer 3

Assuming you have enough local disk space to store the information of all characters, you can mmap one or more files that store all the character data, and create a character object from data in the file(s) only when needed.
If you have neither enough memory nor disk space to store data of all characters locally, then it becomes a much more difficult problem -- you might need to assign to every character an URI and load it from the network...
EDIT: Of course, after updating the character data, you'd need to write it back to the corresponding file. And for performance sake, you might want to implement some caching mechanism so frequently used characters don't need to be read & written back every time they are used.