From: Wolfgang Bangerth Date: Thu, 20 Jan 2022 03:19:55 +0000 (-0700) Subject: Update output. X-Git-Tag: v9.4.0-rc1~575^2 X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=3a609351f75d20cdd946bc872aac4b1a4faa0b46;p=dealii.git Update output. --- diff --git a/examples/step-3/doc/results.dox b/examples/step-3/doc/results.dox index ae8b6c9862..f03e517bd8 100644 --- a/examples/step-3/doc/results.dox +++ b/examples/step-3/doc/results.dox @@ -5,18 +5,21 @@ The output of the program looks as follows: Number of active cells: 1024 Number of degrees of freedom: 1089 DEAL:cg::Starting value 0.121094 -DEAL:cg::Convergence step 48 value 5.33692e-13 +DEAL:cg::Convergence step 36 value 7.07761e-08 @endcode -The first two lines is what we wrote to cout. The last -two lines were generated without our intervention by the CG -solver. The first two lines state the residual at the start of the -iteration, while the last line tells us that the solver needed 47 -iterations to bring the norm of the residual to 5.3e-13, i.e. below -the threshold 1e-12 which we have set in the `solve' function. We will -show in the next program how to suppress this output, which is -sometimes useful for debugging purposes, but often clutters up the -screen display. +The first two lines is what we wrote to std::cout. The last +two lines were generated by the CG solver because we called +`deallog.depth_console(2);` in the `main()` function -- see +the lengthy discussion there. These two lines prefixed by `DEAL:cg:` state +the residual at the start of the +iteration and that the solver needed 36 +iterations to bring the norm of the residual to $7.08\cdot 10^{-8}$, i.e. below +the threshold $\tau$ which we have set in the `solve()` function. +Note that we have asked the residual to be less than $10^{-6}$ times the +norm of the right hand side vector; the starting value is (here) this +norm of the right hand side vector, and there is indeed more than a +factor of $10^{-6}$ between the two values shown. Apart from the output shown above, the program generated the file solution.vtk, which is in the VTK format that is widely