Eigen library novice, do not know why run the following code impassability (seems to fetch out the problem)

 
#include 
#include 
Int main () {

Eigen: : SparseMatrix R; 
R.r esize (50, 50); 
STD: : cout & lt; <1; 
R.c onservativeResize (30, 30); 
STD: : cout & lt; <2; 
} 

Embodied in the output 1 sometimes output 12 then flash back, give advice or comments, thank you!