A ``memory leak'' is when you allocate space for an object in a subroutine but then never free the space when the routine is done. Your program then quickly begins to use up memory as it calls the routine over and over. This not only causes crashes, but also can slow your program dramatically. Take the time now to check your that subroutines have a call to ``free_dvector'' for every call to ``dvector'', and similarly for ``free_dmatrix''.