# Revision history [back]

### What does cohomology_generators actually do?

I don't understand the output of the function "cohomology_generators" of commutative differential graded algebras. Look at this simple exmaple:

A.<x,y,z,t> = GradedCommutativeAlgebra(QQ, degrees = (2,2,1,2))
B = A.cdg_algebra({z:x-y})
B.cohomology_generators(5)

{2: [t, y, x]}


It's apparently telling me that t, x and y are all generators of the cohomology algebra in degree 2. But in cohomology, x = y, since dz = x - y!