Optimizing using grof, interpreting flat profile?

[susan_in_california <bajichuan at hotmail dot com>]

Hello, everyone! I think I have just enough C++ knowledge to write very bad
code, and I would really like to just be better. 

I am writing an algorithm that has to do with solving integer programs, and
thus I am dealing extensively with integer matrices, in particular column
vectors stored as vector<int>. Here is a line from my gprof:

  %   cumulative   self              self     total
 time   seconds   seconds    calls   s/call   s/call  name
 14.33      8.97     4.06 75669549     0.00     0.00  std::vector<int,
std::allocator<int> >::vector(std::vector<int, std::allocator<int> > const&)

I am having a little trouble understanding this line. I have several
functions that are my_func(const vector<int>& my_vec,...). My reasoning was
that the function wouldn't copy the column vector into the parameter in this
case, thus saving me time. But it looks like something is showing up in the
profile. 

Can anyone explain to me what might be happening here? I am better that
there is actually a simple fix to avoid spending 14% of my algorithm in this
function...

Thanks so much for any comments that anyone might have!


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