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Functions for applying boundary conditions to the RHS vector only now accept the solution vector x. Where Dirichlet boundary conditions are applied, b = x - bc.The is useful for applying boundary conditions within Newton iterations. [...]

To: dolfin-dev@xxxxxxxxxx
From: dolfin@xxxxxxxxxx
Date: Thu, 01 Dec 2005 14:16:12 +0100
Reply-to: Discussion of DOLFIN development <dolfin-dev@xxxxxxxxxx>
Sender: "Garth N. Wells" <garth@xxxxxxxxxx>

Commit from garth (2005-12-01 14:16 CET)
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Functions for applying boundary conditions to the RHS vector only now accept the solution vector x. Where Dirichlet boundary conditions are applied, b = x - bc.The is useful for applying boundary conditions within Newton iterations.

This is not consistent with the other applyBC functions which return b = bc (no minus sign). This is due to the definition of the nonlinear function F(u)=0.
For Poisson's equation, I've been using the format F(u) = (grad v,grad u) - (v,f), hence the need for the minus. Is there a preference as to how we set-up nonlinear problems?

Would it be better to use a different name for funtions that return the difference between the current approximate solution and the Dirichlet BC?

  dolfin  src/kernel/fem/FEM.cpp       1.43
  dolfin  src/kernel/fem/dolfin/FEM.h  1.23

Follow ups

Re: Functions for applying boundary conditions to the RHS vector only now accept the solution vector x. Where Dirichlet boundary conditions are applied, b = x - bc.The is useful for applying boundary conditions within Newton iterations. [...]
From: Anders Logg, 2005-12-01