Vectorize large NumPy multiplication

Question

I am interested in calculating a large NumPy array. I have a large array A which contains a bunch of numbers. I want to calculate the sum of different combinati

Answer 1

Instead of dot you could use tensordot. Your current method is equivalent to:

np.tensordot(A, Combinations, [2, 1]).transpose(2, 0, 1)

Note the transpose at the end to put the axes in the correct order.

Like dot, the tensordot function can call down to the fast BLAS/LAPACK libraries (if you have them installed) and so should be perform well for large arrays.