Discussion Groups

Simulation Mechanical and Multiphysics

Reply
Valued Contributor
tfjield
Posts: 98
Registered: ‎06-19-2012

Non positive diagonal entry detected.

238 Views, 2 Replies
10-15-2012 05:19 PM

Anybody know what this means???

 

Non positive diagonal entry detected in ILU method
switch to SSOR Preconditioner.

 

The simulation just stops with no errors or warnings, other than this statement and

 

Error:  Failed in invoking the process: C:\PROGRA~1\Autodesk\SIMULA~1\FRUN03.EXE

 

Model checks report no errors or warnings.  The simulation just ends, with no notifications.

 

Current version of Mechanical & Multiphysics: 2013 SP2 (2013.02.00.0010 2-Oct-2012)
Please use plain text.
Valued Mentor
AstroJohnPE
Posts: 505
Registered: ‎08-30-2012

Re: Non positive diagonal entry detected.

10-17-2012 08:18 AM in reply to: tfjield

Hi Todd,

 

Is this a steady fluid flow or another simulation type?

 

Does the simulation perform some iterations (and maybe even converge?) before you get the message about the SSOR Preconditioner message?

 

And does the message about failing to run FRUN03 occur in the log file immediately after the preconditioner message, or are their other lines of text in between the two?

 

I think the preconditioner is a way to guess at the solution to seed the iterative solver. So switching from one to the other is not a concern.

 

I believe FRUN03 is the fluid flow processor, which I presume was running to get to the preconditioner message. I'm not sure whether it restarts after the preconditioner message and may have some type of timing issue or if it is something else. So please try

  1. You can change the type of solver from iterative to sparse somewhere under the "Setup > Model Setup > Parameters". That would avoid the preconditioner message -- just in case it is somehow involved.
  2. On rare ocassions, the processor will generate a message that does not get put into the log file. The only way to see these messages is to run the analysis from a command prompt (a.k.a. DOS window).  The following instructions are for Win 7 where it is relatively easy to start a command window from the proper location -- which is the folder where the model is located.

a) Start My Computer/Windows Explorer

b) Browse to the folder containing the model (the location of the .FEM file).

c) browse into the model-name.ds_data folder. This is where you will find the the folders for the design scenarios.

d) Hold the shift key and right-click on the design scenario folder for the fluid model, and choose "open command window here".

e) In the command window, type

         C:\PROGRA~1\Autodesk\SIMULA~1\FRUN03.EXE DS -run

where

  • the first part is the path to the executable file FRUN03. Instead of using the DOS 8-character shortcut names, you can also type the complete path and use quotes, such as "C:\Program Files\Autodesk\Simulation 2013\FRUN03.EXE"
  • FRUN03.EXE is the program to run
  • DS is the name of the model that the processor analyzes
  • -run is an option that tells it to run.

Assuming it fails just like before, scroll through the command window to look for any additional messages.

 

John Holtz, PE
Mechanical Engineer
Pittsburgh, PA

16 years experience with Simulation Mechanical
Please use plain text.
Valued Contributor
tfjield
Posts: 98
Registered: ‎06-19-2012

Re: Non positive diagonal entry detected.

10-17-2012 09:32 AM in reply to: AstroJohnPE

Hi John,

 

Thank you for the reply.  I'm running a coupled thermal/fluid flow steady state analysis.

 

The log files typical of what I receive are documented in a previous thread:

 

http://forums.autodesk.com/t5/Autodesk-Simulation-Mechanical/Another-Unexplained-Problem-FRUN03-EXE/...

 

I've tried running the simulations uncoupled, which would be fine for my application, but I don't trust the results.  Please see this thread for an example of the strange results:

 

http://forums.autodesk.com/t5/Autodesk-Simulation-Mechanical/Failed-in-invoking-process-SRUN10-EXE/t...

 

I was able to get the simulation to run without giving me the non-positive diagonal entry error by switching the preconditioner from ILU to SSOR (I think!).  However, this wasn't straightforward.  In the Thermal Analysis settings, it's straightforward to set the preconditioner to SSOR as shown in the following image:

 

Thermal.png

 

If you might remember from a previous thread, for some reason Simulation wants to use the Sparse solver instead of the Iterative.  If I don't change it manually, it will give me an "AlgSolve.exe is not a valid application" error, as we discussed here:

 

http://forums.autodesk.com/t5/Autodesk-Simulation-Mechanical/AlgSolve-exe-is-not-a-valid-application...

 

In the Fluid Analysis paramters I also changed both the Velocity and Pressure Solver Controls to BCSLIB-EXT, as follows:

 

Fluid 2.png

 

But there was one other step that was a bit more difficult...  When the solver is set to Sparse, the preconditioner option is not available:

 

Fluid.png

 

What I had to do to get the simulation to run was to set the solver to Iterative, then change the preconditioner to SSOR, then change it back to sparse.  (I've been fighting with this for weeks, and right now, I don't remember why I couldn't leave it on iterative.)

 

Like I said, a lot of this has been trial and error, so I'm not 100% sure what finally worked.  (I think it was the final change of preconditioner.  Even when everything was set to sparse, I was still getting the ILU/SSOR error.)

 

So that was a minor success.

 

However, the first few of my load cases ran, and then failed on the 5th load case.  Here's the log file:

 

 Autodesk (R) Simulation Steady Coupled Fluid Flow and Thermal Analyses
 Version 2013.02-WIN 02-Oct-2012
 Copyright (c) 2012, Autodesk, Inc. All rights reserved.
      DATE: October 16, 2012
      TIME: 10:11:24 AM


      INPUT MODELS:
      ...inth attempt\choroidal absorption.ds_data\1\ds 

 ****
 **** Iteration starts for velocity and temperature updates 
 ****
 

 For Buoyancy Force ::   LC No. =    2          Total No. of Intvs =    1 
 ------------------------------------------------------------------------ 
 Current      No.        Load  Turbulent  Max. No.  Convergence Tolerance
 Intv No.  Steps   Multiplier      Model    Iters      (Temp.)     (Vel.) 
       1       8    1.00e+000        off      500    1.00e-003  1.00e-003
 ------------------------------------------------------------------------ 

 Intv No.  Step No.  Iter. No.  Euc. Norm (Vel.)   Euc. Norm (Temp.) 
       1         1          1     Rlx =  0.200        Rlx =  0.200  
       1         1          2       3.338e-002          4.687e+000 
       1         1          3       7.336e-003          3.752e+000 
       1         1          4       5.781e-003          3.003e+000 
       1         1          5       4.585e-003          2.403e+000 
       1         1          6       3.666e-003          1.923e+000 
       1         1          7       2.961e-003          1.539e+000 
       1         1          8       2.422e-003          1.231e+000 
       1         1          9       2.009e-003          9.850e-001 
       1         1         10       1.692e-003          7.882e-001 
       1         1         11       1.448e-003          6.306e-001 
       1         1         12       1.258e-003          5.046e-001 
       1         1         13       1.109e-003          4.037e-001 
       1         1         14       9.903e-004          3.230e-001 
       1         1         15       8.936e-004          2.584e-001 
       1         1         16       8.134e-004          2.067e-001 
       1         1         17       7.456e-004          1.654e-001 
       1         1         18       6.871e-004          1.323e-001 
       1         1         19       6.360e-004          1.059e-001 
       1         1         20       5.906e-004          8.470e-002 
       1         1         21       5.499e-004          6.777e-002 
       1         1         22       5.130e-004          5.422e-002 
       1         1         23       4.794e-004          4.337e-002 
       1         1         24       4.487e-004          3.470e-002 
       1         1         25       4.204e-004          2.776e-002 
       1         1         26       3.942e-004          2.221e-002 
       1         1         27       3.700e-004          1.777e-002 
       1         1         28       3.476e-004          1.421e-002 
       1         1         29       3.267e-004          1.137e-002 
       1         1         30       3.072e-004          9.097e-003 
       1         1         31       2.891e-004          7.278e-003 
       1         1         32       2.722e-004          5.822e-003 
       1         1         33       2.563e-004          4.658e-003 
       1         1         34       2.415e-004          3.726e-003 
       1         1         35       2.276e-004          2.981e-003 
       1         1         36       2.146e-004          2.385e-003 
       1         1         37       2.025e-004          1.908e-003 
       1         1         38       1.910e-004          1.526e-003 
       1         1         39       1.803e-004          1.221e-003 
       1         1         40       1.702e-004          9.765e-004 

 >> Current elapsed time =     218.333 minutes 
 

 For Buoyancy Force ::   LC No. =    2          Total No. of Intvs =    1 
 ------------------------------------------------------------------------ 
 Current      No.        Load  Turbulent  Max. No.  Convergence Tolerance
 Intv No.  Steps   Multiplier      Model    Iters      (Temp.)     (Vel.) 
       1       8    1.00e+000        off      500    1.00e-003  1.00e-003
 ------------------------------------------------------------------------ 

 Intv No.  Step No.  Iter. No.  Euc. Norm (Vel.)   Euc. Norm (Temp.) 
       1         2          1     Rlx =  0.200        Rlx =  0.200  
       1         2          2       1.282e-002          6.715e-003 
       1         2          3       1.015e-002          1.126e-002 
       1         2          4       8.034e-003          1.391e-002 
       1         2          5       6.363e-003          1.517e-002 
       1         2          6       5.041e-003          1.545e-002 
       1         2          7       3.994e-003          1.507e-002 
       1         2          8       3.166e-003          1.427e-002 
       1         2          9       2.511e-003          1.321e-002 
       1         2         10       1.991e-003          1.203e-002 
       1         2         11       1.580e-003          1.080e-002 
       1         2         12       1.255e-003          9.589e-003 
       1         2         13       9.971e-004          8.439e-003 
       1         2         14       7.929e-004          7.369e-003 
       1         2         15       6.313e-004          6.392e-003 
       1         2         16       5.032e-004          5.514e-003 
       1         2         17       4.018e-004          4.732e-003 
       1         2         18       3.216e-004          4.044e-003 
       1         2         19       2.581e-004          3.442e-003 
       1         2         20       2.079e-004          2.920e-003 
       1         2         21       1.683e-004          2.469e-003 
       1         2         22       1.369e-004          2.082e-003 
       1         2         23       1.122e-004          1.751e-003 
       1         2         24       9.265e-005          1.470e-003 
       1         2         25       7.722e-005          1.231e-003 
       1         2         26       6.503e-005          1.028e-003 
       1         2         27       5.536e-005          8.580e-004 

 >> Current elapsed time =     367.250 minutes 
 

 For Buoyancy Force ::   LC No. =    2          Total No. of Intvs =    1 
 ------------------------------------------------------------------------ 
 Current      No.        Load  Turbulent  Max. No.  Convergence Tolerance
 Intv No.  Steps   Multiplier      Model    Iters      (Temp.)     (Vel.) 
       1       8    1.00e+000        off      500    1.00e-003  1.00e-003
 ------------------------------------------------------------------------ 

 Intv No.  Step No.  Iter. No.  Euc. Norm (Vel.)   Euc. Norm (Temp.) 
       1         3          1     Rlx =  0.200        Rlx =  0.200  
       1         3          2       1.502e-002          9.643e-003 
       1         3          3       1.189e-002          1.533e-002 
       1         3          4       9.419e-003          1.862e-002 
       1         3          5       7.463e-003          2.015e-002 
       1         3          6       5.915e-003          2.045e-002 
       1         3          7       4.690e-003          1.991e-002 
       1         3          8       3.721e-003          1.883e-002 
       1         3          9       2.954e-003          1.742e-002 
       1         3         10       2.347e-003          1.585e-002 
       1         3         11       1.866e-003          1.424e-002 
       1         3         12       1.486e-003          1.264e-002 
       1         3         13       1.185e-003          1.113e-002 
       1         3         14       9.477e-004          9.718e-003 
       1         3         15       7.598e-004          8.432e-003 
       1         3         16       6.116e-004          7.274e-003 
       1         3         17       4.946e-004          6.245e-003 
       1         3         18       4.026e-004          5.337e-003 
       1         3         19       3.302e-004          4.544e-003 
       1         3         20       2.734e-004          3.855e-003 
       1         3         21       2.288e-004          3.261e-003 
       1         3         22       1.939e-004          2.750e-003 
       1         3         23       1.665e-004          2.313e-003 
       1         3         24       1.449e-004          1.942e-003 
       1         3         25       1.277e-004          1.626e-003 
       1         3         26       1.139e-004          1.359e-003 
       1         3         27       1.027e-004          1.134e-003 
       1         3         28       9.341e-005          9.446e-004 

 >> Current elapsed time =     524.333 minutes 
 

 For Buoyancy Force ::   LC No. =    2          Total No. of Intvs =    1 
 ------------------------------------------------------------------------ 
 Current      No.        Load  Turbulent  Max. No.  Convergence Tolerance
 Intv No.  Steps   Multiplier      Model    Iters      (Temp.)     (Vel.) 
       1       8    1.00e+000        off      500    1.00e-003  1.00e-003
 ------------------------------------------------------------------------ 

 Intv No.  Step No.  Iter. No.  Euc. Norm (Vel.)   Euc. Norm (Temp.) 
       1         4          1     Rlx =  0.200        Rlx =  0.200  
       1         4          2       1.807e-002          1.266e-002 
       1         4          3       1.431e-002          2.029e-002 
       1         4          4       1.134e-002          2.474e-002 
       1         4          5       8.986e-003          2.687e-002 
       1         4          6       7.123e-003          2.735e-002 
       1         4          7       5.649e-003          2.669e-002 
       1         4          8       4.483e-003          2.529e-002 
       1         4          9       3.560e-003          2.345e-002 
       1         4         10       2.829e-003          2.137e-002 
       1         4         11       2.251e-003          1.922e-002 
       1         4         12       1.794e-003          1.709e-002 
       1         4         13       1.433e-003          1.506e-002 
       1         4         14       1.147e-003          1.317e-002 
       1         4         15       9.214e-004          1.144e-002 
       1         4         16       7.436e-004          9.879e-003 
       1         4         17       6.035e-004          8.488e-003 
       1         4         18       4.933e-004          7.261e-003 
       1         4         19       4.069e-004          6.186e-003 
       1         4         20       3.392e-004          5.252e-003 
       1         4         21       2.861e-004          4.445e-003 
       1         4         22       2.446e-004          3.751e-003 
       1         4         23       2.119e-004          3.157e-003 
       1         4         24       1.861e-004          2.651e-003 
       1         4         25       1.655e-004          2.221e-003 
       1         4         26       1.489e-004          1.857e-003 
       1         4         27       1.353e-004          1.550e-003 
       1         4         28       1.239e-004          1.292e-003 
       1         4         29       1.142e-004          1.075e-003 
       1         4         30       1.058e-004          8.926e-004 

 >> Current elapsed time =     687.317 minutes 
 

 For Buoyancy Force ::   LC No. =    2          Total No. of Intvs =    1 
 ------------------------------------------------------------------------ 
 Current      No.        Load  Turbulent  Max. No.  Convergence Tolerance
 Intv No.  Steps   Multiplier      Model    Iters      (Temp.)     (Vel.) 
       1       8    1.00e+000        off      500    1.00e-003  1.00e-003
 ------------------------------------------------------------------------ 

 Intv No.  Step No.  Iter. No.  Euc. Norm (Vel.)   Euc. Norm (Temp.) 
       1         5          1     Rlx =  0.200        Rlx =  0.200  
       1         5          2       2.269e-002          1.725e-002 
       1         5          3       1.797e-002          2.796e-002 
       1         5          4       1.424e-002          3.430e-002 
       1         5          5       1.128e-002          3.741e-002 
       1         5          6       8.946e-003          3.822e-002 
       1         5          7       7.096e-003          3.742e-002 
       1         5          8       5.631e-003          3.556e-002 
       1         5          9       4.472e-003          3.305e-002 
       1         5         10       3.554e-003          3.020e-002 
       1         5         11       2.828e-003          2.721e-002 
       1         5         12       2.254e-003          2.425e-002 
       1         5         13       1.800e-003          2.141e-002 
       1         5         14       1.441e-003          1.875e-002 
       1         5         15       1.158e-003          1.631e-002 
       1         5         16       9.343e-004          1.410e-002 


 **** Error: Temperature update failed. Quit.

 

This is similar to a problem I previously reported in this thread:

 

http://forums.autodesk.com/t5/Autodesk-Simulation-Mechanical/Failed-in-invoking-process-SRUN10-EXE/t...

 

For whatever reason, it appears that Simulation only likes running a few load cases at a time.  As documented in the previous thread, if I change the order of the load cases, I bet the failure has nothing to do with the load case itself and I'll be able to get results.

 

I don't believe this is a resource problem, as I have a ton of hard disk space, 16 gigs of RAM, and 2 quad-core processors, and I'm running the 64 bit versions of Windows 7 and Simulation Multi-Physics.

 

Thank you, John, for the command line info for FRUN03; that may help me debug in the future.

 

Are the command line inputs for all of the FRUNs documented somewhere?  Also, how about the log files?  The report tab doesn't say which Log is which, so I've hunted through the output files and found them, but I'm not sure which ds.xxx file corresponds to which solver.

 

Thank you!!

Todd

Current version of Mechanical & Multiphysics: 2013 SP2 (2013.02.00.0010 2-Oct-2012)
Please use plain text.