147 lines
3.9 KiB
Fortran
147 lines
3.9 KiB
Fortran
c-----------------------------------------------------------------------
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c\BeginDoc
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c
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c\Name: snconv
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c
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c\Description:
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c Convergence testing for the nonsymmetric Arnoldi eigenvalue routine.
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c
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c\Usage:
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c call snconv
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c ( N, RITZR, RITZI, BOUNDS, TOL, NCONV )
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c
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c\Arguments
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c N Integer. (INPUT)
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c Number of Ritz values to check for convergence.
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c
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c RITZR, Real arrays of length N. (INPUT)
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c RITZI Real and imaginary parts of the Ritz values to be checked
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c for convergence.
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c BOUNDS Real array of length N. (INPUT)
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c Ritz estimates for the Ritz values in RITZR and RITZI.
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c
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c TOL Real scalar. (INPUT)
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c Desired backward error for a Ritz value to be considered
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c "converged".
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c
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c NCONV Integer scalar. (OUTPUT)
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c Number of "converged" Ritz values.
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c
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c\EndDoc
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c
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c-----------------------------------------------------------------------
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c
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c\BeginLib
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c
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c\Local variables:
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c xxxxxx real
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c
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c\Routines called:
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c second ARPACK utility routine for timing.
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c slamch LAPACK routine that determines machine constants.
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c slapy2 LAPACK routine to compute sqrt(x**2+y**2) carefully.
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c
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c\Author
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c Danny Sorensen Phuong Vu
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c Richard Lehoucq CRPC / Rice University
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c Dept. of Computational & Houston, Texas
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c Applied Mathematics
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c Rice University
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c Houston, Texas
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c
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c\Revision history:
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c xx/xx/92: Version ' 2.1'
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c
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c\SCCS Information: @(#)
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c FILE: nconv.F SID: 2.3 DATE OF SID: 4/20/96 RELEASE: 2
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c
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c\Remarks
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c 1. xxxx
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c
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c\EndLib
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c
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c-----------------------------------------------------------------------
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c
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subroutine snconv (n, ritzr, ritzi, bounds, tol, nconv)
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c
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c %----------------------------------------------------%
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c | Include files for debugging and timing information |
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c %----------------------------------------------------%
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c
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include 'debug.h'
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include 'stat.h'
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c
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c %------------------%
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c | Scalar Arguments |
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c %------------------%
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c
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integer n, nconv
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Real
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& tol
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c
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c %-----------------%
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c | Array Arguments |
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c %-----------------%
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Real
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& ritzr(n), ritzi(n), bounds(n)
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c
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c %---------------%
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c | Local Scalars |
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c %---------------%
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c
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integer i
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Real
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& temp, eps23
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c
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c %--------------------%
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c | External Functions |
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c %--------------------%
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c
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Real
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& slapy2, slamch
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external slapy2, slamch
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c %-----------------------%
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c | Executable Statements |
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c %-----------------------%
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c
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c %-------------------------------------------------------------%
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c | Convergence test: unlike in the symmetric code, I am not |
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c | using things like refined error bounds and gap condition |
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c | because I don't know the exact equivalent concept. |
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c | |
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c | Instead the i-th Ritz value is considered "converged" when: |
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c | |
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c | bounds(i) .le. ( TOL * | ritz | ) |
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c | |
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c | for some appropriate choice of norm. |
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c %-------------------------------------------------------------%
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c
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call second (t0)
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c
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c %---------------------------------%
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c | Get machine dependent constant. |
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c %---------------------------------%
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c
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eps23 = slamch('Epsilon-Machine')
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eps23 = eps23**(2.0E+0 / 3.0E+0)
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c
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nconv = 0
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do 20 i = 1, n
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temp = max( eps23, slapy2( ritzr(i), ritzi(i) ) )
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if (bounds(i) .le. tol*temp) nconv = nconv + 1
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20 continue
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c
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call second (t1)
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tnconv = tnconv + (t1 - t0)
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c
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return
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c
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c %---------------%
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c | End of snconv |
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c %---------------%
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c
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end
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