Understanding The Output of SolverProxDDP

[Cfather]

Hi,
I'm trying to understand what the outputs of SolverProxDDP mean in each iteration.
There are the following parameters:

alpha
inner_crit
prim_err
dual_err
preg
dphi0
merit
ΔM
aliter
mu

Could someone give me a quick explanation of each parameter? I appreciate it very much!
Specifically, I'm more interested in how the solver converges in terms of costs (different weighted costs considered using addCost) and constraints (dynamics, rigid contacts).