Dirichlet boundary condition in dolfinx

General
1

Hi everyone!
I have the following question about setting the boundary conditions for dolfinx:
Problem ： For mandatory Dirichlet boundary conditions.
Ax=b for example：x2 is known (i.e. Dirichlet boundary condition)
image
In order to obtain a solution that satisfies the Dirichlet boundary.Often, this equation is treated like this：
image
So I want to know how dolfinx achieves this?
By apply_lifting(b,[a],[bcs]) ?

2

Yes, DOLFINx does this by:

  1. Supplying bcs to assemble_matrix, this sets the columns and rows with bcs to the identity row/column
  2. Use apply lifting to get the system above (note still with some rows for the dirichlet bc dofs
  3. Using set_bc to avoid having to do back substitution after solving the problem
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