PSD task in YADE

Dear Bruno Chareyre:
     Thanks for helping me last time and now I am trying to understand all the details of algorithms in O.engine class in Yade just for very basic simulations with DEM and then list all of them. These tasks have not been finished recently. Today my question is about PSD task in Yade.
     In yade, particles generation with a given PSD can be done by these sentences :

##################################################################################
sp0 = pack.SpherePack();
sp0.spmakeCloud(mncorner,mxcorner,num,psdSizes,psdCumm,distributeMass=True)
O.bodies.append([sphere(center and rad in sp0,particles_mat)])
##################################################################################

# psdSizes: sieve sizes for determine particle sizes in test.
# psdCumm: cummulative percentage numbers from 0~100%.

Two questions:
(1).There are two methods for psdCumm, one is based on mass cummulation and the other is based on
number cummulation. I think both of the two can be done in Yade(distributeMass=True or False) but don not know the algorithm and the tranfer relationship between the two.
(2).If I choose (distributeMass=False), can the cummulation mode be transfered from 'mass' to 'number'?

Seeking your help!