Provided by: liblapack-doc_3.3.1-1_all #### NAME

```       LAPACK-3  -  reduces  a real symmetric-definite generalized eigenproblem to standard form,
using packed storage

```

#### SYNOPSIS

```       SUBROUTINE SSPGST( ITYPE, UPLO, N, AP, BP, INFO )

CHARACTER      UPLO

INTEGER        INFO, ITYPE, N

REAL           AP( * ), BP( * )

```

#### PURPOSE

```       SSPGST reduces a real symmetric-definite generalized eigenproblem to standard form,  using
packed storage.
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 SPPTRF.

```

#### ARGUMENTS

```        ITYPE   (input) 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    (input) 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       (input) INTEGER
The order of the matrices A and B.  N >= 0.

AP      (input/output) REAL array, dimension (N*(N+1)/2)
On entry, the upper or lower triangle of the symmetric matrix
A, packed columnwise in a linear array.  The j-th column of A
is stored in the array AP as follows:
if UPLO = 'U', AP(i + (j-1)*j/2) = A(i,j) for 1<=i<=j;
if UPLO = 'L', AP(i + (j-1)*(2n-j)/2) = A(i,j) for j<=i<=n.
On exit, if INFO = 0, the transformed matrix, stored in the
same format as A.

BP      (input) REAL array, dimension (N*(N+1)/2)
The triangular factor from the Cholesky factorization of B,
stored in the same format as A, as returned by SPPTRF.

INFO    (output) INTEGER
= 0:  successful exit
< 0:  if INFO = -i, the i-th argument had an illegal value

LAPACK routine (version 3.3.1)             April 2011                            SSPGST(3lapack)
```