dspgst (l)  Linux Manuals
dspgst: reduces a real symmetricdefinite generalized eigenproblem to standard form, using packed storage
NAME
DSPGST  reduces a real symmetricdefinite generalized eigenproblem to standard form, using packed storageSYNOPSIS
 SUBROUTINE DSPGST(
 ITYPE, UPLO, N, AP, BP, INFO )
 CHARACTER UPLO
 INTEGER INFO, ITYPE, N
 DOUBLE PRECISION AP( * ), BP( * )
PURPOSE
DSPGST reduces a real symmetricdefinite 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.
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

= aqUaq: Upper triangle of A is stored and B is factored as U**T*U; = aqLaq: 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) 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 jth column of A is stored in the array AP as follows: if UPLO = aqUaq, AP(i + (j1)*j/2) = A(i,j) for 1<=i<=j; if UPLO = aqLaq, AP(i + (j1)*(2nj)/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) 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 (output) INTEGER

= 0: successful exit
< 0: if INFO = i, the ith argument had an illegal value