From: Wolfgang Bangerth Date: Sun, 16 Jun 2013 14:17:16 +0000 (+0000) Subject: Document global_dof_index. X-Git-Tag: v8.0.0~288 X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=49d51882c43ed0bdd99f6c9d873678b0f7cfc3b9;p=dealii.git Document global_dof_index. git-svn-id: https://svn.dealii.org/trunk@29821 0785d39b-7218-0410-832d-ea1e28bc413d --- diff --git a/deal.II/examples/step-40/doc/intro.dox b/deal.II/examples/step-40/doc/intro.dox index 5e098c7890..0fec405ec8 100644 --- a/deal.II/examples/step-40/doc/intro.dox +++ b/deal.II/examples/step-40/doc/intro.dox @@ -135,3 +135,15 @@ same number of lines of code (though step-6 spends more space on dealing with coefficients and output). In either case, the comments below will only be on the things that set step-40 apart from step-6 and that aren't already covered in the @ref distributed documentation module. + + +@note This program will be able to compute on as many processors as you want +to throw at it, and for as large a problem as you have the memory and patience +to solve. However, there is a limit: the number of unknowns can not +exceed the largest number that can be stored with an object of type +types::global_dof_index. By default, this is a typedef for unsigned +int, which on most machines today is a 32-bit integer, limiting you to +some 4 billion (in reality, since this program uses PETSc, you will be limited +to half that as PETSc uses signed integers). However, this can be changed +during configuration to use 64-bit integers, see the ReadMe file. This will +give problem sizes you are unlikely to exceed anytime soon.