How/when/where to trigger the computation of the residual

[eriktamsen]

Currently the reaction force sensor assumes that a residual is given, which is hard coded in the linear elastic model, as this uses that sensor. This is not a good solution, just temporary and needs to be fixed

[TTitscher]

We had a similar discussion over at fenics-constitive, I remember. The residual needs to be computed anyways, so I suggest having a residual member where the residual is stored before applying the boundary conditions. This is what I tried for dolfinx here.

One way to evaluate it is to pass this vector to a LoadSensor.__init__ and extract the DOF values in __call__.

[eriktamsen]

will be addressed in fenicsXconcrete