Ansoft Designer Bug:Iterative can't solve more 16500 unkws!!
i use 12h/day Ansoft Designer 1.1 & 2.0, and i discovered that there is a bug in the engine.
Designer cannot solve projects with more than 17000 unknowns using Direct and Iterative solver.
It's really useless setting the values in the solver section for the Direct,Iterative and SVD Decomposition solver methods.
If, for example, you set a project using these criteria for the solver limits:
Limit of 3000 unknowns for Direct Solver and
20000 unknowns for Iterative solver (over 20000 Designer will use the SVD Method but it is really inaccurate, so you have to forget that!!), you will discover that if you plan to solve a problem with 16000 unknowns or more, Designer will display a message "The Planar EM Engine has run out of memory"!!
That's is a serious problem because it drastically reduce the capabilities of the program expecially for large antennas or RF structures.
I think that adding a couple of dwords in the Windows Registry could fix the problem but i'm without experience about.
Please try to solve this very serious problem.
Sincerely
Sirac
TO me, 16500 unknown is already quite impressive. How much time does it take to solve the problem?
I think you can't solve the problem by simply changing some registry entry. All currently available "fast solvers" (FMM or "SVD fast.." etc.) have limits. You just can't expect it to work on problem of any size.
Thanks for the answer...
16500Unknowns is a small project....because if you are realizing an array antenna of 2x2 elements which will work @ 15GHz you really easy will reach problems over 20000 unknowns.
So you can't simulate this problem well!!!
How can i think to simulate an antenna array @ 20GHz???!!
So, if the Designer has this limitations on the solver methods, you can understand that it's perfectly useless to set a solver limit of 20000 about the iterative threshold, if the Iterative Engine cannot solve more than 16500 unknowns.
If i accept to wait very long times to get the solution of a very important project, i can't accept that the program is unavailable to work with 20000 unknowns in a correct way. The SVD Method is not suitable if you want accuracy on simulation data.
PS.And in conclusion, Ansoft's Designer 2.0 license costs 2500$ so i appreciate if a program too expensive can instruct the final user on these absurd limitations!!
Sincerely Sirac
Electrical Engineering University
For MoM 16k unknowns is a very large problem. Remember MoM requires a dense matrix, storing a 16k x 16k complex matrix requires 512 MB of RAM. So if you want to larger problems you will need a more memory.
This is what the SVD fast solve is for. I have solved patch arrays with 80k unknowns and the accuracy is quite good. I am not sure what kind of accuracy you expect, but for us this solver has predicted our measurements.
Although what bothers me most is that a 2x2 element array requires over 16k unknowns. Assuming each element is less than one wavelength in length, it should require less than 225 unknowns per element (15 elements per wavelength). Multiply by four and include the feed network. This should be less than 1.6k unknowns. I would check the mesh, for this size problem, it sounds like you have 10 times to many unknowns. (I say this without having seen you geometry, so this is pure speculation.)
-Wiley
Hi folks,
I am now running Ansoft Designer 2.1.
I would be happy to have a look on the project you are having problem
with.
Some days ago I was running an array with 8 patches
without problem, may be your problem is more related to your model that a general issue.
Gatto
I have talked with ansoft guru...they said it should work as they have given me an example of 100 x 100 array.....
How much memory installed do you have on your PC ?
How much does the solver take ? (see the Windows Task Manager)
Itai
I have an AMD Barton 2500+ FSB 333MHz with 1.3Gb of Ram DDR and at the best (working with 16k of unknowns) the solver can allocate 1Gb of ram memory and 1-1.2Gb of Virtual Memory....That's the maximum for the iterative solver!!
Thanks