Flux-optistruct frequency response

Hi all,

I am having some problems during the frequency response analysis. I have the model of the Electric motor cylinder and I would like to see the frequency response in the certain frequency range.

My first problem has only one force which is applied in the radial way on the rotor. This analysis works fine and is completed in about one minute, very fast.

For the second case I take the same FEM model, and the same frequency range, only the forces are taken from FLUX (which is and Electro magnetic solver) and imported into Optistruct. I have 

around 10000 forces acting in each node separably. This time the analysis takes 2,5 hours. My model is done by this tutorial:

http://www.cedrat.com/fileadmin/user_upload/cedrat_groupe/News_Events/News/VibroAcousticAnalysisWithFluxAndOptiStruct_FINAL.pdf

I went to look into the .stat file, to see which operation takes so much time. it turnd out that there are two opperations:

   Time spent in section : MDPGRAM;  CPU=   23376.27;  WALL=   5846.09

   Time spent in section : MDPREIG;  CPU=    6364.92;  WALL=   2401.62

As you can see this two operations take almost all of the time of the execution.. In my first model with simple forces this same operations took only a second each, so it is here, where the difference comes form.

Could any of you explain what MDPGRAM and  MDPREIG are and if they can be optimized in any way.