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