STL map insertion efficiency: [] vs. insert

Question

There are two ways of map insertion:

m[key] = val;

Or

m.insert(make_pair(key, val));

My question is, which op

Answer 1

We have to refine the analysis by mentioning that the relative performance depends on the type(size) of the objects being copied as well.

I did a similar experiment (to nbt) with a map of (int -> set). I know it is a terrible thing to do, but, illustrative for this scenario. The "value", in this case a set of ints, has 20 elements in it.

I execute a million iterations of the []= Vs. insert operations and do RDTSC/iter-count.

[] = set | 10731 cycles

insert(make_pair<>) | 26100 cycles

It shows the magnitude of penalty added due to the copying. Of course, CPP11(move ctor's) will change the picture.