| 843 | | In case of a run using several PEs and the multigrid method for solving the Poisson equation for perturbation pressure (see [#psolver psolver]), the value of this parameter defines on which grid level the data are gathered on PE0 in order to allow for a further coarsening of the grid. The finest grid defines the largest grid level. By default, the gathering level is determined automatically and displayed in file [../iofiles#RUN_CONTROL RUN_CONTROL]. It is only possible to gather data from a level larger than the one determined automatically. A test run may be necessary to determine this level.\\\\ |
| 844 | | Setting of '''mg_switch_to_pe0_level''' = -''1'' prevents that data are collected on PE0 at all, i.e. coarsening of grids is limited by the subdomains. |
| | 843 | In case of a run using several PEs and the multigrid method for solving the Poisson equation for perturbation pressure (see [#psolver psolver]), the value of this parameter defines on which grid level the data are gathered on PE0 in order to allow for a further coarsening of the grid. The finest grid defines the largest grid level. If '''mg_switch_to_pe0_level''' = ''0'', the gathering level is determined automatically and displayed in file [../iofiles#RUN_CONTROL RUN_CONTROL]. It is only possible to gather data from a level larger than the one determined automatically. A test run may be necessary to determine this level.\\\\ |
| | 844 | Default setting is '''mg_switch_to_pe0_level''' = -''1'', which prevents that data are collected on PE0 at all, i.e. coarsening of grids is limited by the subdomains. \\\\ |
| | 845 | '''Remark:''' The default setting is significantly faster compared to automatically determining or explicitly prescribing '''mg_switch_to_pe0_level'''. Even though the divergence reduction of the multigrid solver is slightly smaller with the default setting, gathering on PE0 does not justify the additional cost so far. |
