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Modify the Problem Dependent Variables

  To set up the proper storage and to arrange for effective use of the IRLM 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 a eigenvalue cluster. The only restriction is that nev must be less than ncv. The recommended initial 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.3.
 
Table A.3: The eigenvalues of interest for symmetric eigenvalue problems.
   
which EIGENVALUES
   
'LA' Largest (algebraic) eigenvalues.
'SA' Smallest (algebraic) eigenvalues.
'LM' Largest eigenvalues in magnitude.
'SM' Smallest eigenvalues in magnitude.
'BE' Eigenvalue at both ends. When nev
  is odd, compute one more from the
  high end than from the low end.

When a spectral transformation is employed, only the selections 'BE', 'LA' or 'SA' should be used.

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 + 1 ncv
are satisfied.



 
next up previous contents index
Next: Other Variables Up: Symmetric Drivers Previous: Driver dsdrv6
Chao Yang
11/7/1997