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man pages->IRIX man pages -> complib/TRED1 (3)
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### Contents

```
_TRED1(3F)							    _TRED1(3F)

```

### NAME[Toc][Back]

```     TRED1, STRED1   -	EISPACK	routine.  This subroutine reduces a REAL
SYMMETRIC matrix to a symmetric tridiagonal matrix	using orthogonal
similarity	transformations.

```

### SYNOPSYS[Toc][Back]

```	  subroutine  tred1(nm,	n, a, d, e, e2)
integer	   nm, n
double precision a(nm,n), d(n), e(n),	e2(n)

subroutine  sred1(nm,	n, a, d, e, e2)
integer	   nm, n
real		   a(nm,n), d(n), e(n),	e2(n)

```

### DESCRIPTION[Toc][Back]

```     On	Input

NM	must be	set to the row dimension of two-dimensional array parameters
as	declared in the	calling	program	dimension statement.

N is the order of the matrix.

A contains	the real symmetric input matrix.  Only the lower triangle of
the matrix	need be	supplied.  On Output

A contains	information about the orthogonal trans-	formations used	in the
reduction in its strict lower triangle.  The full upper triangle of A is
unaltered.

D contains	the diagonal elements of the tridiagonal matrix.

E contains	the subdiagonal	elements of the	tridiagonal matrix in its last
N-1 positions.  E(1) is set to zero.

E2	contains the squares of	the corresponding elements of E. E2 may
coincide with E if	the squares are	not needed.  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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