From: bangerth Date: Sat, 2 Feb 2008 02:58:46 +0000 (+0000) Subject: Add 2d output. Add a few sentences. X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4ce2b9734222891015e7bb63124e50c1efc5c52d;p=dealii-svn.git Add 2d output. Add a few sentences. git-svn-id: https://svn.dealii.org/trunk@15705 0785d39b-7218-0410-832d-ea1e28bc413d --- diff --git a/deal.II/examples/step-31/doc/intro.dox b/deal.II/examples/step-31/doc/intro.dox index aaa90cd687..34a85e260b 100644 --- a/deal.II/examples/step-31/doc/intro.dox +++ b/deal.II/examples/step-31/doc/intro.dox @@ -445,8 +445,27 @@ direct solver such as UMFPACK inefficient: only for problem sizes of a few 10,000 to maybe 100,000 unknowns can a sparse decomposition be computed using reasonable time and memory resources. -SO WHAT TO DO HERE? +What we do in that case is to use an incomplete LU decomposition (ILU) as a +preconditioner, rather than actually computing complete LU factors. As it so +happens, deal.II has a class that does this: SparseILU. Computing the ILU +takes a time that only depends on the number of nonzero entries in the sparse +matrix (or that we are willing to fill in the LU factors, if these should be +more than the ones in the matrix), but is independent of the bandwidth of the +matrix. It is therefore an operation that can efficiently also be computed in +3d. On the other hand, an incomplete LU decomposition, by definition, does not +represent an exact inverse of the matrix $A$. Consequently, preconditioning +with the ILU will still require more than one iteration, unlike +preconditioning with the sparse direct solver. The inner solver will therefore +take more time when multiplying with the Schur complement, a tradeoff +unavoidable. + - +

Implementation

+ +Note anything here that would be particular about this program. + + +

The testcase

+Describe the testcase we are dealing with here. diff --git a/deal.II/examples/step-31/doc/results.dox b/deal.II/examples/step-31/doc/results.dox index b54aab4203..f1248247be 100644 --- a/deal.II/examples/step-31/doc/results.dox +++ b/deal.II/examples/step-31/doc/results.dox @@ -2,6 +2,59 @@

Results

+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
+ @image html step-31.2d.mesh-0.png + + @image html step-31.2d.mesh-1.png +
+ @image html step-31.2d.mesh-2.png + + @image html step-31.2d.mesh-3.png +
+ @image html step-31.2d.mesh-4.png + + @image html step-31.2d.mesh-5.png +
+ @image html step-31.2d.mesh-6.png + +
+ +@image html step-31.2d.solution.png + + + + + Output in 3d: @code Refinement cycle 0 @@ -61,23 +114,57 @@ Refinement cycle 6 15 CG Schur complement iterations for pressure. @endcode +Note that the number of (outer) iterations does not increase as we refine the +mesh. + Compute times for each iteration alone: seconds, seconds, 1 minute, 8 minutes, 33 minutes, 3h37, 24h55 Pictures -@image html step-31.3d.mesh-0.png - -@image html step-31.3d.mesh-1.png + + + + + + + + + + + + + + + + + + + + + + + + +
+ @image html step-31.3d.mesh-0.png + + @image html step-31.3d.mesh-1.png +
+ @image html step-31.3d.mesh-2.png + + @image html step-31.3d.mesh-3.png +
+ @image html step-31.3d.mesh-4.png + + @image html step-31.3d.mesh-5.png +
+ @image html step-31.3d.mesh-6.png + +
-@image html step-31.3d.mesh-2.png - -@image html step-31.3d.mesh-3.png +@image html step-31.3d.solution.png -@image html step-31.3d.mesh-4.png -@image html step-31.3d.mesh-5.png -@image html step-31.3d.mesh-6.png -@image html step-31.3d.solution.png diff --git a/deal.II/examples/step-31/doc/step-31.2d.mesh-0.png b/deal.II/examples/step-31/doc/step-31.2d.mesh-0.png new file mode 100644 index 0000000000..ddf20d89d1 Binary files /dev/null and b/deal.II/examples/step-31/doc/step-31.2d.mesh-0.png differ diff --git a/deal.II/examples/step-31/doc/step-31.2d.mesh-1.png b/deal.II/examples/step-31/doc/step-31.2d.mesh-1.png new file mode 100644 index 0000000000..c651723c41 Binary files /dev/null and b/deal.II/examples/step-31/doc/step-31.2d.mesh-1.png differ diff --git a/deal.II/examples/step-31/doc/step-31.2d.mesh-2.png b/deal.II/examples/step-31/doc/step-31.2d.mesh-2.png new file mode 100644 index 0000000000..b4619e230d Binary files /dev/null and b/deal.II/examples/step-31/doc/step-31.2d.mesh-2.png differ diff --git a/deal.II/examples/step-31/doc/step-31.2d.mesh-3.png b/deal.II/examples/step-31/doc/step-31.2d.mesh-3.png new file mode 100644 index 0000000000..fd8c36e15b Binary files /dev/null and b/deal.II/examples/step-31/doc/step-31.2d.mesh-3.png differ diff --git a/deal.II/examples/step-31/doc/step-31.2d.mesh-4.png b/deal.II/examples/step-31/doc/step-31.2d.mesh-4.png new file mode 100644 index 0000000000..0aaf74b888 Binary files /dev/null and b/deal.II/examples/step-31/doc/step-31.2d.mesh-4.png differ diff --git a/deal.II/examples/step-31/doc/step-31.2d.mesh-5.png b/deal.II/examples/step-31/doc/step-31.2d.mesh-5.png new file mode 100644 index 0000000000..357bc6aee0 Binary files /dev/null and b/deal.II/examples/step-31/doc/step-31.2d.mesh-5.png differ diff --git a/deal.II/examples/step-31/doc/step-31.2d.solution.png b/deal.II/examples/step-31/doc/step-31.2d.solution.png new file mode 100644 index 0000000000..f21edb5136 Binary files /dev/null and b/deal.II/examples/step-31/doc/step-31.2d.solution.png differ