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SSPGV(3F)							     SSPGV(3F)


NAME    [Toc]    [Back]

     SSPGV - compute all the eigenvalues and, optionally, the eigenvectors of
     a real generalized	symmetric-definite eigenproblem, of the	form
     A*x=(lambda)*B*x, A*Bx=(lambda)*x,	or B*A*x=(lambda)*x

SYNOPSIS    [Toc]    [Back]

     SUBROUTINE	SSPGV( ITYPE, JOBZ, UPLO, N, AP, BP, W,	Z, LDZ,	WORK, INFO )

	 CHARACTER     JOBZ, UPLO

	 INTEGER       INFO, ITYPE, LDZ, N

	 REAL	       AP( * ),	BP( * ), W( * ), WORK( * ), Z( LDZ, * )

PURPOSE    [Toc]    [Back]

     SSPGV computes all	the eigenvalues	and, optionally, the eigenvectors of a
     real generalized symmetric-definite eigenproblem, of the form
     A*x=(lambda)*B*x,	A*Bx=(lambda)*x,  or B*A*x=(lambda)*x.	Here A and B
     are assumed to be symmetric, stored in packed format, and B is also
     positive definite.

ARGUMENTS    [Toc]    [Back]

     ITYPE   (input) INTEGER
	     Specifies the problem type	to be solved:
	     = 1:  A*x = (lambda)*B*x
	     = 2:  A*B*x = (lambda)*x
	     = 3:  B*A*x = (lambda)*x

     JOBZ    (input) CHARACTER*1
	     = 'N':  Compute eigenvalues only;
	     = 'V':  Compute eigenvalues and eigenvectors.

     UPLO    (input) CHARACTER*1
	     = 'U':  Upper triangles of	A and B	are stored;
	     = 'L':  Lower triangles of	A and B	are stored.

     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 jth
	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)*(2*n-j)/2)	= A(i,j) for j<=i<=n.

	     On	exit, the contents of AP are destroyed.

     BP	     (input/output) REAL array,	dimension (N*(N+1)/2)
	     On	entry, the upper or lower triangle of the symmetric matrix B,
	     packed columnwise in a linear array.  The j-th column of B	is



									Page 1






SSPGV(3F)							     SSPGV(3F)



	     stored in the array BP as follows:	 if UPLO = 'U',	BP(i + (j1)*j/2)
 = B(i,j) for 1<=i<=j; if UPLO = 'L', BP(i + (j-1)*(2*nj)/2)
 = B(i,j) for	j<=i<=n.

	     On	exit, the triangular factor U or L from	the Cholesky
	     factorization B = U**T*U or B = L*L**T, in	the same storage
	     format as B.

     W	     (output) REAL array, dimension (N)
	     If	INFO = 0, the eigenvalues in ascending order.

     Z	     (output) REAL array, dimension (LDZ, N)
	     If	JOBZ = 'V', then if INFO = 0, Z	contains the matrix Z of
	     eigenvectors.  The	eigenvectors are normalized as follows:	 if
	     ITYPE = 1 or 2, Z**T*B*Z =	I; if ITYPE = 3, Z**T*inv(B)*Z = I.
	     If	JOBZ = 'N', then Z is not referenced.

     LDZ     (input) INTEGER
	     The leading dimension of the array	Z.  LDZ	>= 1, and if JOBZ =
	     'V', LDZ >= max(1,N).

     WORK    (workspace) REAL array, dimension (3*N)

     INFO    (output) INTEGER
	     = 0:  successful exit
	     < 0:  if INFO = -i, the i-th argument had an illegal value
	     > 0:  SPPTRF or SSPEV returned an error code:
	     <=	N:  if INFO = i, SSPEV failed to converge; i off-diagonal
	     elements of an intermediate tridiagonal form did not converge to
	     zero.  > N:   if INFO = n + i, for	1 <= i <= n, then the leading
	     minor of order i of B is not positive definite.  The
	     factorization of B	could not be completed and no eigenvalues or
	     eigenvectors were computed.
SSPGV(3F)							     SSPGV(3F)


NAME    [Toc]    [Back]

     SSPGV - compute all the eigenvalues and, optionally, the eigenvectors of
     a real generalized	symmetric-definite eigenproblem, of the	form
     A*x=(lambda)*B*x, A*Bx=(lambda)*x,	or B*A*x=(lambda)*x

SYNOPSIS    [Toc]    [Back]

     SUBROUTINE	SSPGV( ITYPE, JOBZ, UPLO, N, AP, BP, W,	Z, LDZ,	WORK, INFO )

	 CHARACTER     JOBZ, UPLO

	 INTEGER       INFO, ITYPE, LDZ, N

	 REAL	       AP( * ),	BP( * ), W( * ), WORK( * ), Z( LDZ, * )

PURPOSE    [Toc]    [Back]

     SSPGV computes all	the eigenvalues	and, optionally, the eigenvectors of a
     real generalized symmetric-definite eigenproblem, of the form
     A*x=(lambda)*B*x,	A*Bx=(lambda)*x,  or B*A*x=(lambda)*x.	Here A and B
     are assumed to be symmetric, stored in packed format, and B is also
     positive definite.

ARGUMENTS    [Toc]    [Back]

     ITYPE   (input) INTEGER
	     Specifies the problem type	to be solved:
	     = 1:  A*x = (lambda)*B*x
	     = 2:  A*B*x = (lambda)*x
	     = 3:  B*A*x = (lambda)*x

     JOBZ    (input) CHARACTER*1
	     = 'N':  Compute eigenvalues only;
	     = 'V':  Compute eigenvalues and eigenvectors.

     UPLO    (input) CHARACTER*1
	     = 'U':  Upper triangles of	A and B	are stored;
	     = 'L':  Lower triangles of	A and B	are stored.

     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 jth
	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)*(2*n-j)/2)	= A(i,j) for j<=i<=n.

	     On	exit, the contents of AP are destroyed.

     BP	     (input/output) REAL array,	dimension (N*(N+1)/2)
	     On	entry, the upper or lower triangle of the symmetric matrix B,
	     packed columnwise in a linear array.  The j-th column of B	is



									Page 1






SSPGV(3F)							     SSPGV(3F)



	     stored in the array BP as follows:	 if UPLO = 'U',	BP(i + (j1)*j/2)
 = B(i,j) for 1<=i<=j; if UPLO = 'L', BP(i + (j-1)*(2*nj)/2)
 = B(i,j) for	j<=i<=n.

	     On	exit, the triangular factor U or L from	the Cholesky
	     factorization B = U**T*U or B = L*L**T, in	the same storage
	     format as B.

     W	     (output) REAL array, dimension (N)
	     If	INFO = 0, the eigenvalues in ascending order.

     Z	     (output) REAL array, dimension (LDZ, N)
	     If	JOBZ = 'V', then if INFO = 0, Z	contains the matrix Z of
	     eigenvectors.  The	eigenvectors are normalized as follows:	 if
	     ITYPE = 1 or 2, Z**T*B*Z =	I; if ITYPE = 3, Z**T*inv(B)*Z = I.
	     If	JOBZ = 'N', then Z is not referenced.

     LDZ     (input) INTEGER
	     The leading dimension of the array	Z.  LDZ	>= 1, and if JOBZ =
	     'V', LDZ >= max(1,N).

     WORK    (workspace) REAL array, dimension (3*N)

     INFO    (output) INTEGER
	     = 0:  successful exit
	     < 0:  if INFO = -i, the i-th argument had an illegal value
	     > 0:  SPPTRF or SSPEV returned an error code:
	     <=	N:  if INFO = i, SSPEV failed to converge; i off-diagonal
	     elements of an intermediate tridiagonal form did not converge to
	     zero.  > N:   if INFO = n + i, for	1 <= i <= n, then the leading
	     minor of order i of B is not positive definite.  The
	     factorization of B	could not be completed and no eigenvalues or
	     eigenvectors were computed.


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