How to accumulate pixel values in Jitter/Jit.Gen world ?

I would like to learn the best approach to accumulate/sum pixel values in jitter/jit.gen world.
Imagine the hypothetical matrices:

M1= [0 0 1 1 2 2 2 2] this is coordinates;
M2= [1 1 1 1 1 1 1 1] this is values;

From the positions of the numbers in M1 I wish to sum all the values in M2 that share the same position.
In this example the result would be [2 2 4].

Before you reply use ZL objects, yes, I know how to do it in the Max landscape, but I wish to know how to do it in the jitter and jit.gen landscape, if it is possible.
Perhaps with codebox?

Thank you All!