How to use functools.reduce to improve the performance of populating a dictionary?

I am new to the field of parallelizing and optimizing data mining modules in Python and I have a question about parallelizing populating a dictionary. I am actually doing an inverted indexing using values scored in a two dimensional matrix m. The code works fine but I would like to apply python reduce to make it run faster.

Here is my code:

def createInvertedIndex(matrix):
    dic={}
    for i in range(len(matrix[0])):
        if matrix[1][i] in dic.keys():
            dic[matrix[1][i]].append(matrix[0][i])
        else: 
            dic[matrix[1][i]]=list([matrix[0][i]]) 
    return dic