| 278 | 278 | ||[=#PA0236 PA0236] ||grid coarsening on subdomain level cannot be performed || The multigrid pressure solver halfs the number of grid points in each direction to get coarser grid levels. This is done for the subdomains on each PE until one of the directions cannot be divided by 2 without rest. If this is the case, the coarsest grid level of each subdomain are gathered on each PE for further coarsening. Before gathering, the coarsening must be done for the subdomain at least one time. You get this error messages for example with the following combination: \\ [../inipar#nx nx ] = 60, [../inipar#ny ny ] = 60, [../inipar#nz nz ] = 60, \\ [../d3par#npex npex ] = 4, [../d3par#npey npey ] = 2. \\ With this combination, the subdomain on each PE has the size: \\ nx = 15, ny = 30, nz = 60. \\ The number of grid points in the x-direction of the subdomain cannot be divided by 2 and no coarsening is possible for the subdomains in this example. \\\\ To avoid this error ensure that the number of grid points in each direction can be divided by 2 without rest on the subdomain of an PE at least one time. Therefor vary the number of grid points for the direction which does not fit by changing [../inipar#nx nx ], [../inipar#ny ny ] or [../inipar#nz nz ] or adjust the number of processors by modifying the parameters [../d3par#npex npex ] or [../d3par#npey npey ] in order to get other subdomain sizes. \\ In the example given above, you can avoid the error by changing nx or npex. For example setting [../inipar#nx nx ] = 64 leads to a subdomain of \\ nx = 16, ny = 30, nz = 60. \\ All numbers are now divisible by 2 without rest and the first coarser grid on the subdomain is then: \\ nx = 8, ny = 15, nz = 30. || |
