title: pass by reference c++
body: <p>My teacher in c++ told me that call by reference should only be used if I'm not going to change anything on the arrays inside the function.
  I have some really big vectors that I'm passing around in my program. All the vectors will be modified inside the functions. My matrices are of sizes about <code>[256*256][256][50]</code>...</p>
  
  <p>Is there some particular reason not to use call-by reference here?</p>
  
  <p>AFAIK call by reference should be way faster and consume less memory?</p>