title: How to achieve a matrix from vectorized sum of each row in a matrix with another matrix
body: <p>Suppose we have A as <code>A=[[0,0,0],[1,1,1]]</code> and <code>B=[[1,1,1],[2,2,2],[3,3,3]]</code> how can i write a vectorized implementation with no for loops in numpy to calculate matrix C as <code>C=[[6,6,6],[7,7,7]]</code>?
  C is created from summing each row in A with all rows in B.</p>