Dear all,

I am working with a large nonlinear system solved with SNES, where a 
significant fraction of the unknowns are temporarily inactive due to a physical 
parameter being zero (e.g. zero occupancy / zero weight).


For those DOF the corresponding equilibrium equation is physically inactive, 
but the unknown still appears in the global vector and in couplings of 
neighboring particles (Im using dmswarm).

At the moment, these inactive equations contribute with a zero residual 
(F_i=0), which (I think) leads to poor conditioning and convergence issues for 
large problems.


My question is about best numerical practice in this situation. For the 
position field, should I do something like F_i = q_i - q_(i,n)? Where q_(i,n) 
is the position of the particle at the previous configuration.


Best regards,

Miguel

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