Select the Mesh decomposition and optimization menu item.

  Mesh decomposition and optimization

Define the decomposition:

1. If both decomposition methods are available, select the one you want to use by choosing the appropriate menu item:

     Select Metis decomposer

   or

     Select Chaco decomposer

   To disable decomposition, select the Disable decomposition into sub-parts menu item. To reenable it, you can choose Enable decomposition into sub-parts.

   Disabling decomposition is not recommended for large 3D meshes. For simple 2D meshes, however, decomposition will not result in significant performance improvements, so you can disable it; you should, however, still optimize the element numbering, which significantly affects the solver performance, even in 2D.

2. Modify the number of sub-parts, if you want to change from the default of 16 sub-parts.

     Modify the number of sub-parts

   Typically, optimal performance is obtained when the number of elements in each sub-part is between 250 and 500. For example, on a mesh with 20,000 elements, the fastest solution is obtained with 16 or 32 sub-parts. Note that the optimal number of sub-parts does not depend on the number of variables being solved in each element. While switching from a generalized Newtonian flow problem to a viscoelastic flow problem increases the number of solution variables significantly, the optimal number of sub-parts will remain the same.

Define the optimization:

1. If both optimization methods are available, select the one you want to use by choosing the appropriate menu item:

     Select Cuthill McKee optimiser

   or

     Select Chaco optimiser

   If you are using the Chaco decomposition method, the Chaco optimization method is recommended.

   To disable optimization altogether, select the Disable numbering optimization menu item. To reenable it, you can choose Enable numbering optimization. Disabling the numbering optimization is not recommended.

2. Indicate whether the average or the maximum frontal width should be optimized by selecting the appropriate menu item:

     Optimize the maximum frontal width (memory size)

   or

     Optimize the average frontal width (CPU time)

   Optimizing the average wavefront minimizes the CPU time, and optimizing the maximum wavefront reduces the memory requirements. In most cases, however, optimizing for one criterion will result in optimization for the other as well.

3. If you are using the Chaco optimization method, modify the optimization algorithm parameters, if necessary. In most cases, there will be no need to change these parameters.

     Options for optimization

   (This menu item is not available when the Cuthill-McKee algorithm is used.)

   •   Modify the tolerance factor sets the tolerance parameter that the Chaco algorithm uses for optimizing the numbering.

   •   Modify the weight on elements controls the relative importance of variables located within sub-parts with respect to variables located at the interface between sub-parts. The default value reduces the length of the interfaces as much as possible.

   •   Modify the weight on Schur variables controls the relative importance of variables located at the interface between sub-parts with respect to variables within sub-parts. The default value reduces the length of the interfaces as much as possible.

Specify the cost evaluation parameters.

  Options for cost evaluation

The cost evaluation is a qualitative evaluation of the relative acceleration a given mesh decomposition is likely to yield, based on an operations count for a single linear scalar variable. The comparison of the value obtained by not taking decomposition into account to the value obtained with decomposition is an order of magnitude representation of the estimated acceleration.

By default, Ansys Polydata will evaluate and report the cost of the new mesh numbering, taking into account the decomposition into sub-parts. To report the cost evaluation based on the nondecomposed mesh, select Do not take sub-domains decomposition into account. To report the cost evaluation for the original mesh numbering, select Do not take numbering optimization into account.

You can turn off the cost evaluation report by selecting the Disable cost evaluation menu item instead of the Options for cost evaluation menu item. The cost evaluation will still be performed, but the results will not be reported.

Specify the name of the original mesh file.

  Enter the filename of the initial mesh

Specify the name of the file where the optimized and/or decomposed mesh should be saved.

  Enter the filename of the new mesh

You can overwrite the original mesh file by specifying the same name, but it may be safer to save the new mesh to a different file.

Check the settings listed at the top of the Mesh decomposition and optimization menu to be sure that they are correct, and repeat the appropriate step(s) above to make any corrections.

Perform the decomposition and/or optimization.

  Run computation...