DSPGST 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 DPPTRF.

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.

AP

          AP is DOUBLE PRECISION 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

          BP is DOUBLE PRECISION 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 DPPTRF.

INFO

          INFO is INTEGER


          = 0:  successful exit


          < 0:  if INFO = -i, the i-th argument had an illegal value

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

December 2016