Eigenvalue analysis exceeds workspace/array storage

divamva · Post by **divamva** » Thu Jul 14, 2005 8:03 pm

I have a moderately large 3D frame, 5 stories X 5bays X 5 bays

When trying to do eigenvalue analysis, I seem to hit some array allocation problem, the Opensees response being:
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BandArpackSolver::Error with _saupd info = -9999
Could not build an Arnoldi factorization. IPARAM(5) returns the size of the current Arnoldi factorization. The user is advised to check that enough workspace and array storage has been allocated.
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I believe nothing is wrong with my structure since if I remove the last story, everything is just fine!

Any ideas on how to get over this?

silvia · Post by **silvia** » Sat Jul 16, 2005 10:50 pm

it is some quirky thing with the eigensolver, you need more dof's than you want.
add a 10e-9 mass at another free dof.
let me know if this helps.

divamva · Post by **divamva** » Sun Jul 17, 2005 6:40 pm

Yes you are right, there do exist minor modifications that make this go away. In my case I modified some of the support conditions (for reasons unrelated to this particular problem) thus decreasing the dofs by about 3 and the error went away!

I haven't tried the mass trick that you suggested though.