# dsygst.f man page

dsygst.f

## Synopsis

### Functions/Subroutines

subroutine dsygst (ITYPE, UPLO, N, A, LDA, B, LDB, INFO)
DSYGST

## Function/Subroutine Documentation

### subroutine dsygst (integer ITYPE, character UPLO, integer N, double precision, dimension( lda, * ) A, integer LDA, double precision, dimension( ldb, * ) B, integer LDB, integer INFO)

DSYGST

Purpose:

``` DSYGST reduces a real symmetric-definite generalized eigenproblem
to standard form.

If ITYPE = 1, the problem is A*x = lambda*B*x,
and A is overwritten by inv(U**T)*A*inv(U) or inv(L)*A*inv(L**T)

If ITYPE = 2 or 3, the problem is A*B*x = lambda*x or
B*A*x = lambda*x, and A is overwritten by U*A*U**T or L**T*A*L.

B must have been previously factorized as U**T*U or L*L**T by DPOTRF.```
Parameters:

ITYPE

```          ITYPE is INTEGER
= 1: compute inv(U**T)*A*inv(U) or inv(L)*A*inv(L**T);
= 2 or 3: compute U*A*U**T or L**T*A*L.```

UPLO

```          UPLO is CHARACTER*1
= 'U':  Upper triangle of A is stored and B is factored as
U**T*U;
= 'L':  Lower triangle of A is stored and B is factored as
L*L**T.```

N

```          N is INTEGER
The order of the matrices A and B.  N >= 0.```

A

```          A is DOUBLE PRECISION array, dimension (LDA,N)
On entry, the symmetric matrix A.  If UPLO = 'U', the leading
N-by-N upper triangular part of A contains the upper
triangular part of the matrix A, and the strictly lower
triangular part of A is not referenced.  If UPLO = 'L', the
leading N-by-N lower triangular part of A contains the lower
triangular part of the matrix A, and the strictly upper
triangular part of A is not referenced.

On exit, if INFO = 0, the transformed matrix, stored in the
same format as A.```

LDA

```          LDA is INTEGER
The leading dimension of the array A.  LDA >= max(1,N).```

B

```          B is DOUBLE PRECISION array, dimension (LDB,N)
The triangular factor from the Cholesky factorization of B,
as returned by DPOTRF.```

LDB

```          LDB is INTEGER
The leading dimension of the array B.  LDB >= max(1,N).```

INFO

```          INFO is INTEGER
= 0:  successful exit
< 0:  if INFO = -i, the i-th argument had an illegal value```
Author:

Univ. of Tennessee

Univ. of California Berkeley

NAG Ltd.

Date:

December 2016

Definition at line 129 of file dsygst.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page dsygst(3) is an alias of dsygst.f(3).

Tue Nov 14 2017 Version 3.8.0 LAPACK