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Tips for Working with Large Models

What is perceived to be a 'large model' will vary between Modeller and Solver and the operations being performed, and also between one PC and another.  Large models here are simply defined as those which:

  • Are reaching or exceeding the limits of the available resources on the PC (disk space, memory, speed or graphics)
  • Experience long times for certain pre-processing, meshing, solving or post-processing tasks
  • Create large model files (*.mdl) or results files (*.mys)
  • On 32bit LUSAS on a 64bit PC, require close to or more than the 4GB limit for a 32bit application on a 64bit machine

Some tips for working with large models are as follows:

  1. Ensure that the model is saved locally on the PC and not on a network drive.

  2. Ensure that the local drive where the model is saved has plenty of free space and that the drive is sufficiently defragmented.  For a linear analysis run for example, the minimum amount of free space suggested is 12GB or 10 times the size of the results file that would be created, whichever is the larger amount. The more free space the better as it can reduce the time taken to write large files like the results file and output files during the Solver run.

  3. Start simple with a coarse mesh – It is recommended to start with a simple model and build in complexities one at a time. Reasonable idealisations of the structure to be modelled should always be considered, reducing modelling, solving and post-processing time for efficient analysis to suit the requirements. Starting with a simple model and coarse mesh will allow quick checking of behaviour of the model and help to identify any problems/mistakes in the modelling. The modelling and mesh can then be refined when the model is to give a suitable and stable solution before perform longer and more accurate solution runs before actually obtaining and assessing the results.

  4. Solve a static linear elastic analysis with the Frontal Solver – This serves as a general check of the model. The standard Frontal solver will also check the model more thoroughly, reporting errors in the Solver Output file "*.out" file, which can be opened using a text editor such as Notepad by right-clicking on the analysis name in the Analyses tab of the Treeview and then by choosing “View Solver Output File. . . ”. Find (Ctrl+F on your keyboard) can be used to search for "***", this will jump to any errors, warnings and other messages in the file. Problem areas can then be investigated using Advanced Selection (Edit menu) in Modeller to select nodes and elements referenced in the error. To use the Frontal solver; go to File menu > Model Properties... then the Solution tab and Solver Options... then set the type to "Frontal". This solver does take a bit longer to run as it performs checks on the model and reports messages. See the user area page for common errors and warnings.

  5. Running “In memory” - Ensure that the PC has sufficient RAM so that Modeller and Solver can run "in memory" - this will allow them to run much faster. Please see the page regarding hardware considerations for more information. 

  6. Close any other applications that are running on the PC, and LUSAS Modeller. Then start Modeller again and open your model. This will help to ensure Modeller is able to use the RAM on your PC.

  7. Dedicated Graphics card - If you are likely to be working with large models frequently it is recommended to invest in a good graphics card, optimised for OpenGL with a large amount of its own memory. 

  8. Graphics settings - If the PC already has a separately installed graphics card, choose the "Hardware OpenGL drivers" graphics option for LUSAS (via Start>All Programs>LUSAS V1x.x>Tools>Configuration Utility>Graphics tab) and also ensure that Hardware Acceleration is being used for the display (available via the Control Panel in the Advanced Settings for the Display) to get the most out of the graphics card. For an integrated display card, or if OpenGL errors are encountered regarding memory, LUSAS recommend using the "Advanced software OpenGL drivers" graphics option instead. 

  9. Use the Manual Refresh option (Window menu > Manual Refresh) to freeze redraws when several changes to the display or to the model are to be made, without refreshing the display after each one. Use F5 to refresh the display when ready.

  10. Backup the model regularly - Save the model regularly and particularly after making significant changes, perhaps incrementing the name of the file each time ("Model_001.mdl", "Model_002.mdl", etc) so that it is easy to return to a particular stage of model development should the need arise. There is also an "Auto backup" facility which keeps backups of the last two saved copies of the model by default. Settings for changing the number of backups kept, or to additionally save a further backup to a network location as well are available via File menu > Model Properties > Backup tab.

  11. Lock the mesh whilst making several changes to the geometry to prevent remeshing after each change. The mesh can locked via Utilities menu > Mesh > Mesh Lock).  Unlock the mesh when the changes have been all been made to force a remesh. Whilst making changes to the geometry it is also worth removing the Mesh Layer. When you are ready to mesh the model, reset the mesh first (Utilities menu > Mesh > Mesh Reset) and then unlock the mesh (Utilities menu > Mesh > Mesh Lock).

  12. Run Solver without Modeller - When solving the model, you can run Solver without Modeller or any other application running. This will free up physical memory available as Modeller grabs a large amount of memory whilst it is open. To do this:

    1. When you are ready to solve your model, go to File menu >Export Solver Datafile… 

    2. Use the default Datafile name and browse to the location of the model and then to the folder \Associated Model Data\<Model filename>.

    3. Click "Save". This will create a Datafile (.dat) in the default location for results associated with your model.

    4. Now save the model and close Modeller and any other applications.

    5. If required, the Datafile can be opened in a text editor such as Notepad at this stage..

    6. The Datafile can then saved and be run in Solver without Modeller open by going to Start > All Programs > LUSAS1x.x > LUSAS Solver and a black cmd prompt window will appear

    7. Drag and drop the Datafile for into the cmd prompt window that appears and press Return/Enter on the keyboard. This will then start Solver solving your model.

The results file generated can then be opened on top of your model in Modeller. From V15 onwards, if you have a model with the same name as the results and the results are saved in the \Associated Data\<Model filename>, go to File menu > Open Available Results Files to open the results on top of the model.

  1. Use 64bit Solver and 64bit Modeller for post-processing – Any 32bit application is limited to 4GB of memory (2^32), but 64bit applications will be able to use as much memory as is available on the PC and this will mean larger models can be created and solved, but also there may be a gain in speed if the model is moderately large but not exceeding 32bit limits. A model can be created in 32bit Modeller, solved in 64bit Solver and then post-processed in 32bit Modeller, or 64bit Modeller. It can also be setup such that the 64bit Solver is always used when clicking the green equals button in 32bit Modeller (see the Installation Guide for further details). There are no restrictions on the compatibility (in terms of translation) of results files and Datafiles between 32bit and 64bit.

  2. Fast Solvers - In general for solvign large models, it is strongly suggested to purchase our fast solvers, which can reduce the solving time, by a factor of 5 to 10.

  3. Limit the parts of the model visible – This will help generally with the responsiveness of Modeller, but also to perform post-processing more quickly for smaller groups of features/mesh by setting these groups to “Set as only visible”. This particularly applies where a variety of different element types have been used, as in this model. Group element types separately. For example, only have volume mesh visible when creating a contour plot for SE for Solids.

  4. Un-tick "Show visibility feedback in treeview" – This is a tick box at the bottom of the Groups tab of the Treeview. When it is on, groups in the Treeview are colour coded to show where that group is currently fully or partially visible or whether it is invisible. Turning this of means Modeller does not colour code the groups in the Treeview.

  5. Deselect View menu> Show Datatips – Datatips are information windows that appear when hovering over an item in the graphics window. Turning this off (at least when not needed) should make Modeller a little more responsive.

  6. Minimise the information displayed - Some ways this can be done are as follows:

    1. Turn off the display of layers that are not wanted on.

    2. Hide the display of loading, or supports if not required. For example, the visualisation of a body force or distributed loading assigned to large volumes or surfaces will show a loading arrow at each node in the model. The visualisation of loads and supports can be turned on/off using the appropriate toolbar buttons, for more control over their display the Properties of the Attributes layer can be adjusted.

    3. Opt not to display “Hidden parts” for the Mesh and Geometry layers

    4. Show mesh as “Outline Only”

    5. Show Values/Labels of selection only rather than all nodes, elements and features at once.

    See also the page regarding reducing recalculation in LUSAS Modeller.

  7. Hard drives

    • If you have two local hard drives, then save your model on the one that does not have LUSAS installed on it. 

    • If you have three local drives have LUSAS installed on one, the model saved on another, and your temporary file locations set on the third.

    A solid state drive (SSD) will generally be a lot faster than a normal hard disk drive and this can shorten the Solver run time by speeding up the reading and writing of files.  Further guidance regarding pc specification.

  8. Reduce the size of the model to send to support - To reduce the size of the model to send to support for further guidance, save a copy of the model without the mesh:

    1. Save your model (File menu > Save) first

    2. Save a copy of the model to send to support by going to File menu > Save As

    3. Go to Utilities menu > Mesh > Mesh Lock

    4. Then Utilities menu > Mesh > Mesh Reset to remove the mesh.

    5. Save the copy now without mesh (File menu > Save) and email the model to Support@lusas.com.

Warning! - Make sure that the mesh is saved with the main copy of the model that is to continue to be worked with, otherwise it will remesh each time the model is opened. Also, if the model has been solved already, the results cannot be opened on top of the model if the model has been meshed again since solving.

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