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subroutine rs(nm,n,a,w,matz,z,fv1,fv2,ierr)
c
integer n,nm,ierr,matz
double precision a(nm,n),w(n),z(nm,n),fv1(n),fv2(n)
c
c this subroutine calls the recommended sequence of
c subroutines from the eigensystem subroutine package (eispack)
c to find the eigenvalues and eigenvectors (if desired)
c of a real symmetric matrix.
c
c on input
c
c nm must be set to the row dimension of the two-dimensional
c array parameters as declared in the calling program
c dimension statement.
c
c n is the order of the matrix a.
c
c a contains the real symmetric matrix.
c
c matz is an integer variable set equal to zero if
c only eigenvalues are desired. otherwise it is set to
c any non-zero integer for both eigenvalues and eigenvectors.
c
c on output
c
c w contains the eigenvalues in ascending order.
c
c z contains the eigenvectors if matz is not zero.
c
c ierr is an integer output variable set equal to an error
c completion code described in the documentation for tqlrat
c and tql2. the normal completion code is zero.
c
c fv1 and fv2 are temporary storage arrays.
c
c questions and comments should be directed to burton s. garbow,
c mathematics and computer science div, argonne national laboratory
c
c this version dated august 1983.
c
c ------------------------------------------------------------------
c
if (n .le. nm) go to 10
ierr = 10 * n
go to 50
c
10 if (matz .ne. 0) go to 20
c .......... find eigenvalues only ..........
call tred1(nm,n,a,w,fv1,fv2)
* tqlrat encounters catastrophic underflow on the Vax
* call tqlrat(n,w,fv2,ierr)
call tql1(n,w,fv1,ierr)
go to 50
c .......... find both eigenvalues and eigenvectors ..........
20 call tred2(nm,n,a,w,fv1,z)
call tql2(nm,n,w,fv1,z,ierr)
50 return
end
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