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c-----------------------------------------------------------------------
c\BeginDoc
c
c\Name: snconv
c
c\Description:
c Convergence testing for the nonsymmetric Arnoldi eigenvalue routine.
c
c\Usage:
c call snconv
c ( N, RITZR, RITZI, BOUNDS, TOL, NCONV )
c
c\Arguments
c N Integer. (INPUT)
c Number of Ritz values to check for convergence.
c
c RITZR, Real arrays of length N. (INPUT)
c RITZI Real and imaginary parts of the Ritz values to be checked
c for convergence.
c BOUNDS Real array of length N. (INPUT)
c Ritz estimates for the Ritz values in RITZR and RITZI.
c
c TOL Real scalar. (INPUT)
c Desired backward error for a Ritz value to be considered
c "converged".
c
c NCONV Integer scalar. (OUTPUT)
c Number of "converged" Ritz values.
c
c\EndDoc
c
c-----------------------------------------------------------------------
c
c\BeginLib
c
c\Local variables:
c xxxxxx real
c
c\Routines called:
c arscnd ARPACK utility routine for timing.
c wslamch LAPACK routine that determines machine constants.
c wslapy2 LAPACK routine to compute sqrt(x**2+y**2) carefully.
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\Revision history:
c xx/xx/92: Version ' 2.1'
c
c\SCCS Information: @(#)
c FILE: nconv.F SID: 2.3 DATE OF SID: 4/20/96 RELEASE: 2
c
c\Remarks
c 1. xxxx
c
c\EndLib
c
c-----------------------------------------------------------------------
c
subroutine snconv (n, ritzr, ritzi, bounds, tol, nconv)
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
integer n, nconv
Real
& tol
c
c %-----------------%
c | Array Arguments |
c %-----------------%
Real
& ritzr(n), ritzi(n), bounds(n)
c
c %---------------%
c | Local Scalars |
c %---------------%
c
integer i
Real
& temp, eps23
c
c %--------------------%
c | External Functions |
c %--------------------%
c
Real
& wslapy2, wslamch
external wslapy2, wslamch
c %-----------------------%
c | Executable Statements |
c %-----------------------%
c
c %-------------------------------------------------------------%
c | Convergence test: unlike in the symmetric code, I am not |
c | using things like refined error bounds and gap condition |
c | because I don't know the exact equivalent concept. |
c | |
c | Instead the i-th Ritz value is considered "converged" when: |
c | |
c | bounds(i) .le. ( TOL * | ritz | ) |
c | |
c | for some appropriate choice of norm. |
c %-------------------------------------------------------------%
c
call arscnd (t0)
c
c %---------------------------------%
c | Get machine dependent constant. |
c %---------------------------------%
c
eps23 = wslamch('Epsilon-Machine')
eps23 = eps23**(2.0E+0 / 3.0E+0)
c
nconv = 0
do 20 i = 1, n
temp = max( eps23, wslapy2( ritzr(i), ritzi(i) ) )
if (bounds(i) .le. tol*temp) nconv = nconv + 1
20 continue
c
call arscnd (t1)
tnconv = tnconv + (t1 - t0)
c
return
c
c %---------------%
c | End of snconv |
c %---------------%
c
end
|
