Changes between Version 64 and Version 65 of doc/app/initialization_parameters

Timestamp:

Sep 14, 2010 11:45:18 AM (14 years ago)

Author:

kanani

Comment:

--

doc/app/initialization_parameters

@@ -562 +562 @@
 By default, the optimization method depends on the host on which PALM is running. On machines with vector-type CPUs, single 3d-loops are used to calculate each tendency term of each prognostic equation, while on all other machines, all prognostic equations are solved within one big loop over the two horizontal indices {{{i}}} and {{{j}}} (giving a good cache uitilization).\\\\
 The default behaviour can be changed by setting either '''loop_optimization''' = '' 'vector' '' or '''loop_optimization''' = '' 'cache'.''
+}}}
+|----------------
+{{{#!td style="vertical-align:top"
+[=#mg_cycles '''mg_cycles''']
+}}}
+{{{#!td style="vertical-align:top"
+I
+}}}
+{{{#!td style="vertical-align:top"
+-1
+}}}
+{{{#!td
+Number of cycles to be used with the multi-grid scheme.\\\\
+This parameter determines the number of cycles to be carried out in the multi-grid method used for solving the Poisson equation for perturbation pressure (see [#psolver psolver]). The type of the cycles can be set with [#cycle_mg cycle_mg].\\\\
+By default ('''mg_cyles''' = -''1''), the number of cycles depends on the requested accuracy of the scheme (see [#residual_limit residual_limit]) and may vary from time step to time step. In this case, the CPU time for a run will be difficult to estimate, since it heavily depends on the total number of the cycles to be carried out.\\\\
+By assigning '''mg_cycles''' a value (>= ''1''), the number of cycles can be fixed so that the CPU time can be clearly estimated.\\\\
+'''Note:'''\\ 
+When using a fixed number of cycles, the user must examine the local file [../iofiles#RUN_CONTROL RUN_CONTROL] regularly to check whether the divergence of the velocity field is sufficiently reduced by the pressure solver. It should be reduced at least by two orders of magnitude. For cyclic boundary conditions along both horizontal directions (see [#bc_lr bc_lr] and [#bc_ns bc_ns]) '''mg_cycles''' = ''2'' is typically a good choice, for non-cyclic lateral boundary conditions '''mg_cycles''' = ''4'' may be sufficient.
+}}}
+|----------------
+{{{#!td style="vertical-align:top"
+[=#mg_switch_to_pe0_level '''mg_switch_to_pe0_level''']
+}}}
+{{{#!td style="vertical-align:top"
+I
+}}}
+{{{#!td style="vertical-align:top"
+
+}}}
+{{{#!td
+Grid level at which data shall be gathered on PE0.\\\\
+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 neccessary to determine this level.\\\\
+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.
+}}}
+|----------------
+{{{#!td style="vertical-align:top"
+[=#<insert_parameter_name> '''<insert_parameter_name>''']
+}}}
+{{{#!td style="vertical-align:top"
+<insert type>
+}}}
+{{{#!td style="vertical-align:top"
+<insert value>
+}}}
+{{{#!td
+<insert explanation>
+}}}
+|----------------
+{{{#!td style="vertical-align:top"
+[=#<insert_parameter_name> '''<insert_parameter_name>''']
+}}}
+{{{#!td style="vertical-align:top"
+<insert type>
+}}}
+{{{#!td style="vertical-align:top"
+<insert value>
+}}}
+{{{#!td
+<insert explanation>
+}}}
+|----------------
+{{{#!td style="vertical-align:top"
+[=#<insert_parameter_name> '''<insert_parameter_name>''']
+}}}
+{{{#!td style="vertical-align:top"
+<insert type>
+}}}
+{{{#!td style="vertical-align:top"
+<insert value>
+}}}
+{{{#!td
+<insert explanation>
 }}}
 |----------------