SSPGST - reduce 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
= '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 sym
metric 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.
The triangular factor from the Cholesky factoriza
tion 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 ille
gal value
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