From: Wolfgang Bangerth Date: Mon, 14 Oct 2013 20:56:11 +0000 (+0000) Subject: Fix typo. X-Git-Tag: v8.1.0~593 X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e54406454a37d1f3f32c13bac024472763ec2f21;p=dealii.git Fix typo. git-svn-id: https://svn.dealii.org/trunk@31231 0785d39b-7218-0410-832d-ea1e28bc413d --- diff --git a/deal.II/examples/step-20/doc/intro.dox b/deal.II/examples/step-20/doc/intro.dox index dd4c3829ca..13476bc201 100644 --- a/deal.II/examples/step-20/doc/intro.dox +++ b/deal.II/examples/step-20/doc/intro.dox @@ -400,10 +400,10 @@ also a full matrix. On the other hand, the CG algorithm doesn't require us to actually have a representation of $S$, it is sufficient to form matrix-vector products with it. We can do so in steps: to compute $Sv=B^TM^{-1}Bv=B^T(M^{-1}(Bv))$, we
    -
  1. form $w = T v$; +
  2. form $w = B v$;
  3. solve $My = w$ for $y=M^{-1}w$, using the CG method applied to the positive definite and symmetric mass matrix $M$; -
  4. form $z=B^Ty$ to obtain $Sv=z$. +
  5. form $z=B^Ty$ to obtain $z=Sv$.
Note how we evaluate the expression $B^TM^{-1}Bv$ right to left to avoid matrix-matrix products; this way, all we have to do is evaluate