179 lines
5.4 KiB
Fortran
179 lines
5.4 KiB
Fortran
c\BeginDoc
|
|
c
|
|
c\Name: cngets
|
|
c
|
|
c\Description:
|
|
c Given the eigenvalues of the upper Hessenberg matrix H,
|
|
c computes the NP shifts AMU that are zeros of the polynomial of
|
|
c degree NP which filters out components of the unwanted eigenvectors
|
|
c corresponding to the AMU's based on some given criteria.
|
|
c
|
|
c NOTE: call this even in the case of user specified shifts in order
|
|
c to sort the eigenvalues, and error bounds of H for later use.
|
|
c
|
|
c\Usage:
|
|
c call cngets
|
|
c ( ISHIFT, WHICH, KEV, NP, RITZ, BOUNDS )
|
|
c
|
|
c\Arguments
|
|
c ISHIFT Integer. (INPUT)
|
|
c Method for selecting the implicit shifts at each iteration.
|
|
c ISHIFT = 0: user specified shifts
|
|
c ISHIFT = 1: exact shift with respect to the matrix H.
|
|
c
|
|
c WHICH Character*2. (INPUT)
|
|
c Shift selection criteria.
|
|
c 'LM' -> want the KEV eigenvalues of largest magnitude.
|
|
c 'SM' -> want the KEV eigenvalues of smallest magnitude.
|
|
c 'LR' -> want the KEV eigenvalues of largest REAL part.
|
|
c 'SR' -> want the KEV eigenvalues of smallest REAL part.
|
|
c 'LI' -> want the KEV eigenvalues of largest imaginary part.
|
|
c 'SI' -> want the KEV eigenvalues of smallest imaginary part.
|
|
c
|
|
c KEV Integer. (INPUT)
|
|
c The number of desired eigenvalues.
|
|
c
|
|
c NP Integer. (INPUT)
|
|
c The number of shifts to compute.
|
|
c
|
|
c RITZ Complex array of length KEV+NP. (INPUT/OUTPUT)
|
|
c On INPUT, RITZ contains the the eigenvalues of H.
|
|
c On OUTPUT, RITZ are sorted so that the unwanted
|
|
c eigenvalues are in the first NP locations and the wanted
|
|
c portion is in the last KEV locations. When exact shifts are
|
|
c selected, the unwanted part corresponds to the shifts to
|
|
c be applied. Also, if ISHIFT .eq. 1, the unwanted eigenvalues
|
|
c are further sorted so that the ones with largest Ritz values
|
|
c are first.
|
|
c
|
|
c BOUNDS Complex array of length KEV+NP. (INPUT/OUTPUT)
|
|
c Error bounds corresponding to the ordering in RITZ.
|
|
c
|
|
c
|
|
c
|
|
c\EndDoc
|
|
c
|
|
c-----------------------------------------------------------------------
|
|
c
|
|
c\BeginLib
|
|
c
|
|
c\Local variables:
|
|
c xxxxxx Complex
|
|
c
|
|
c\Routines called:
|
|
c csortc ARPACK sorting routine.
|
|
c ivout ARPACK utility routine that prints integers.
|
|
c second ARPACK utility routine for timing.
|
|
c cvout ARPACK utility routine that prints vectors.
|
|
c
|
|
c\Author
|
|
c Danny Sorensen Phuong Vu
|
|
c Richard Lehoucq CRPC / Rice University
|
|
c Dept. of Computational & Houston, Texas
|
|
c Applied Mathematics
|
|
c Rice University
|
|
c Houston, Texas
|
|
c
|
|
c\SCCS Information: @(#)
|
|
c FILE: ngets.F SID: 2.2 DATE OF SID: 4/20/96 RELEASE: 2
|
|
c
|
|
c\Remarks
|
|
c 1. This routine does not keep complex conjugate pairs of
|
|
c eigenvalues together.
|
|
c
|
|
c\EndLib
|
|
c
|
|
c-----------------------------------------------------------------------
|
|
c
|
|
subroutine cngets ( ishift, which, kev, np, ritz, bounds)
|
|
c
|
|
c %----------------------------------------------------%
|
|
c | Include files for debugging and timing information |
|
|
c %----------------------------------------------------%
|
|
c
|
|
include 'debug.h'
|
|
include 'stat.h'
|
|
c
|
|
c %------------------%
|
|
c | Scalar Arguments |
|
|
c %------------------%
|
|
c
|
|
character*2 which
|
|
integer ishift, kev, np
|
|
c
|
|
c %-----------------%
|
|
c | Array Arguments |
|
|
c %-----------------%
|
|
c
|
|
Complex
|
|
& bounds(kev+np), ritz(kev+np)
|
|
c
|
|
c %------------%
|
|
c | Parameters |
|
|
c %------------%
|
|
c
|
|
Complex
|
|
& one, zero
|
|
parameter (one = (1.0E+0, 0.0E+0), zero = (0.0E+0, 0.0E+0))
|
|
c
|
|
c %---------------%
|
|
c | Local Scalars |
|
|
c %---------------%
|
|
c
|
|
integer msglvl
|
|
c
|
|
c %----------------------%
|
|
c | External Subroutines |
|
|
c %----------------------%
|
|
c
|
|
external cvout, csortc, second
|
|
c
|
|
c %-----------------------%
|
|
c | Executable Statements |
|
|
c %-----------------------%
|
|
c
|
|
c %-------------------------------%
|
|
c | Initialize timing statistics |
|
|
c | & message level for debugging |
|
|
c %-------------------------------%
|
|
c
|
|
call second (t0)
|
|
msglvl = mcgets
|
|
c
|
|
call csortc (which, .true., kev+np, ritz, bounds)
|
|
c
|
|
if ( ishift .eq. 1 ) then
|
|
c
|
|
c %-------------------------------------------------------%
|
|
c | Sort the unwanted Ritz values used as shifts so that |
|
|
c | the ones with largest Ritz estimates are first |
|
|
c | This will tend to minimize the effects of the |
|
|
c | forward instability of the iteration when the shifts |
|
|
c | are applied in subroutine cnapps. |
|
|
c | Be careful and use 'SM' since we want to sort BOUNDS! |
|
|
c %-------------------------------------------------------%
|
|
c
|
|
call csortc ( 'SM', .true., np, bounds, ritz )
|
|
c
|
|
end if
|
|
c
|
|
call second (t1)
|
|
tcgets = tcgets + (t1 - t0)
|
|
c
|
|
if (msglvl .gt. 0) then
|
|
call ivout (logfil, 1, kev, ndigit, '_ngets: KEV is')
|
|
call ivout (logfil, 1, np, ndigit, '_ngets: NP is')
|
|
call cvout (logfil, kev+np, ritz, ndigit,
|
|
& '_ngets: Eigenvalues of current H matrix ')
|
|
call cvout (logfil, kev+np, bounds, ndigit,
|
|
& '_ngets: Ritz estimates of the current KEV+NP Ritz values')
|
|
end if
|
|
c
|
|
return
|
|
c
|
|
c %---------------%
|
|
c | End of cngets |
|
|
c %---------------%
|
|
c
|
|
end
|