Estimating Run Time And File  Sizes For ANSYS Solutions

For “small to moderately sized” ANSYS models with little added analysis complexity, most users will simply initiate the solution. However, for larger models, or for analyses with complicated nonlinear options, you may feel more comfortable knowing what to expect before initiating solution. For example, how long will your analysis take to solve and how much disk space will you need before you run it? How much memory will your analysis need? While there is no exact method of predicting these quantities, the ANSYS program can estimate them in its RUNSTAT module. The RUNSTAT module is a processor, or routine, of its own. You can enter it by issuing the /RUNSTAT (Main Menu>Run-Time Stats) command at the Begin level. The RUNSTAT module estimates run times and other statistics based on information in the database. Therefore, you must define the model geometry (nodes, elements, etc.), loads and load options, and analysis options before you enter RUNSTAT. It is best to use RUNSTAT immediately before solving. Estimating Run Time To estimate the run time, the ANSYS program needs your computer’s performance information: MIPS (millions of instructions per second), MFLOPs (millions of floating point operations per second), etc. To obtain this information, use the RSPEED command (Main Menu>Run-Time Stats>System Settings). If you do not know such details about your computer, you can execute the macro SETSPEED, which issues the appropriate RSPEED command for you. For more information about the SETSPEED macro, see Section 3.7 of the ANSYS Operations Guide. The other piece of information needed to estimate the total run time is the number of iterations (or load steps in a linear, static analysis) for the analysis. To get this information, use the RITER command (Main Menu>Run-Time Stats>Iter Setting). To obtain an estimate of run time, use the RTIMST command (Main Menu>Run-Time Stats>Individual Stats). Based on information supplied by the RSPEED and RITER commands and the model information in the database, the RTIMST command gives you a run time estimate. Estimating File Size The RFILSZ command estimates the size of the following files: .ESAV, .EMAT, .EROT, .TRI, .FULL, .RST, .RTH, .RMG, and .RFL. The GUI equivalent for RFILSZ is the same as for RTIMST. The estimate of the results files is based on one set of results (one substep). You will need to multiply it by the estimated number of results written for the actual results file sizes. Estimating Memory Requirements The RWFRNT command (Main Menu>Run-Time Stats>Individual Stats) gives wavefront estimates and memory requirements for solution. You can then request that amount of memory using the ANSYS launcher. The RWFRNT command automatically reorders the elements if no reordering has previously been done. If an iterative solver is selected for solution, memory estimates will be based on the selected solver. Other RUNSTAT commands are RSTAT, which gives model statistics (node and element information); RMEMRY, which gives memory statistics; and RALL (Main Menu>Run-Time Stats>All Statistics), which is a convenience command that executes the RSTAT, RWFRNT, RTIMST, and RMEMRY commands. The GUI equivalent for all these commands except for RALL is Main Menu>Run-Time Stats>Individual Stats.

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