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Modify the Problem Dependent Variables

  To set up the proper storage and to arrange for effective use of the IRAM various parameters will have to be set. These variables include: The variable nev may be set to be a value larger than the number of eigenvalues desired to avoid splitting an eigenvalue cluster. The only restriction is that nev must be less than ncv. The recommended choice of ncv is to set ncv = 2 nev. The user is encouraged to experiment with both nev and ncv. The possible choices for the input variable which are listed in Table A.6.
 
Table A.6: The eigenvalues of interest for non-symmetric eigenvalue problems.
   
which EIGENVALUES
   
'LM' Largest magnitude
'SM' Smallest magnitude
'LR' Largest real parts
'SR' Smallest real parts
'LI' Largest imaginary parts
'SI' Smallest imaginary parts

When using a spectral transformation, the selection of which = 'SM' should be avoided.

Once the above variables are modified, the storage declarations

      integer          maxn, maxnev, maxncv, ldv
      parameter       (maxn=256, maxnev=10, maxncv=25, ldv=maxn )
should be adjusted so that the conditions
n maxn,
nev maxnev,
ncv maxncv,
nev+2 ncv
are satisfied. The last condition on nev is needed to assure that complex conjugate pairs of eigenvalues are kept together.



 
next up previous contents index
Next: Other Variables Up: Real Nonsymmetric Drivers Previous: Driver dndrv6
Chao Yang
11/7/1997