Efficient way of matching entities to systems in an entity component system

Question

I\'m working on a data-oriented entity component system where component types and system signatures are known at compile-time.

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An entity

Answer 1

Regarding the pseudo code:

for(auto& e : entities)
    for(const auto& s : signatures)
         if((e.bitset & s.bitset) == s.bitset)
             callUserFunction(e);

I am unsure why you need the inner loop.

If you have the requested signature in the function then you can get the bitset of that signature and there is no need to iterate over all of the signatures.

template 
void forEntitiesMatching(const std::function& fun)
{
    for(auto& e : entities)
        if((e.bitset & T::get_bitset()) == T::get_bitset())
             fun(e);
}