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man pages->IRIX man pages -> complib/REDUC2 (3)
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### Contents

```
_REDUC2(3F)							   _REDUC2(3F)

```

### NAME[Toc][Back]

```     REDUC2, SREDUC2  -	 EISPACK routine.  This	subroutine reduces the
generalized SYMMETRIC eigenproblems ABx=(LAMBDA)x OR BAy=(LAMBDA)y, where
B is POSITIVE DEFINITE, to	the standard symmetric eigenproblem using the
Cholesky factorization of B.

```

### SYNOPSYS[Toc][Back]

```	  subroutine  reduc2(nm, n, a, b, dl, ierr)
integer	   nm, n, ierr
double precision a(nm,n), b(nm,n), dl(n)

subroutine sreduc2(nm, n, a, b, dl, ierr)
integer	   nm, n, ierr
real		   a(nm,n), b(nm,n), dl(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 matrices A and B.  If the Cholesky factor L of B is
already available,	N should be prefixed with a minus sign.

A AND B contain the real symmetric	input matrices.	 Only the full upper
triangles of the matrices need be supplied.  If N is negative, the	strict
lower triangle of B contains, instead, the	strict lower triangle of its
Cholesky factor L.

DL	contains, if N is negative, the	diagonal elements of L.	On Output

A contains	in its full lower triangle the full lower triangle of the
symmetric matrix derived from the reduction to the	standard form.	The
strict upper triangle of A	is unaltered.

B contains	in its strict lower triangle the strict	lower triangle of its
Cholesky factor L.	 The full upper	triangle of B is unaltered.

DL	contains the diagonal elements of L.

IERR is set to Zero       for normal return, 7*N+1	     if	B is not
positive definite.	 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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