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man pages->IRIX man pages -> complib/TQL1 (3)
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Contents

```
_TQL1(3F)							     _TQL1(3F)

```

NAME[Toc][Back]

```     TQL1, STQL1    -  EISPACK routine.	 This subroutine finds the eigenvalues
of	a SYMMETRIC TRIDIAGONAL	matrix by the QL method.

```

SYNOPSYS[Toc][Back]

```	  subroutine  tql1(n, d, e, ierr)
integer	      n, ierr
double precision d(n), e(n)

subroutine stql1(n, d, e, ierr)
integer	      n, ierr
real	      d(n), e(n)

```

DESCRIPTION[Toc][Back]

```     On	Input

N is the order of the matrix.

D contains	the diagonal elements of the input matrix.

E contains	the subdiagonal	elements of the	input matrix in	its last N-1
positions.	 E(1) is arbitrary.  On	Output

D contains	the eigenvalues	in ascending order.  If	an error exit is made,
the eigenvalues are correct and ordered for indices 1,2,...IERR-1,	but
may not be	the smallest eigenvalues.

E has been	destroyed.

IERR is set to Zero       for normal return, J	     if	the J-th
eigenvalue	has not	been
determined after 30 iterations.	 Calls PYTHAG(A,B) for sqrt(A**2 +
B**2).  Questions and comments should be directed to B. S.	Garbow,
APPLIED MATHEMATICS DIVISION, ARGONNE NATIONAL LABORATORY

PPPPaaaaggggeeee 1111```
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