dsygv man page on Scientific

Man page or keyword search:  
man Server   26626 pages
apropos Keyword Search (all sections)
Output format
Scientific logo
[printable version]

DSYGV(1)	      LAPACK driver routine (version 3.2)	      DSYGV(1)

NAME
       DSYGV  - 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

SYNOPSIS
       SUBROUTINE DSYGV( ITYPE, JOBZ, UPLO, N, A, LDA, B, LDB, W, WORK, LWORK,
			 INFO )

	   CHARACTER	 JOBZ, UPLO

	   INTEGER	 INFO, ITYPE, LDA, LDB, LWORK, N

	   DOUBLE	 PRECISION A( LDA, * ), B( LDB, * ), W( * ), WORK( * )

PURPOSE
       DSYGV 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 and B is also
       positive definite.

ARGUMENTS
       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.

       A       (input/output) DOUBLE PRECISION array, dimension (LDA, N)
	       On  entry,  the symmetric matrix A.  If UPLO = 'U', the leading
	       N-by-N upper triangular part of A contains the upper triangular
	       part  of the matrix A.  If UPLO = 'L', the leading N-by-N lower
	       triangular part of A contains the lower triangular part of  the
	       matrix A.  On exit, if JOBZ = 'V', then if INFO = 0, A 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 on exit the upper  tri‐
	       angle  (if  UPLO='U') or the lower triangle (if UPLO='L') of A,
	       including the diagonal, is destroyed.

       LDA     (input) INTEGER
	       The leading dimension of the array A.  LDA >= max(1,N).

       B       (input/output) DOUBLE PRECISION array, dimension (LDB, N)
	       On entry, the symmetric positive definite matrix B.  If UPLO  =
	       'U', the leading N-by-N upper triangular part of B contains the
	       upper triangular part of the matrix B.	If  UPLO  =  'L',  the
	       leading	N-by-N	lower  triangular part of B contains the lower
	       triangular part of the matrix B.	 On exit, if INFO  <=  N,  the
	       part  of B containing the matrix is overwritten by the triangu‐
	       lar factor U or L from the Cholesky factorization B = U**T*U or
	       B = L*L**T.

       LDB     (input) INTEGER
	       The leading dimension of the array B.  LDB >= max(1,N).

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

       WORK	  (workspace/output)   DOUBLE	PRECISION   array,   dimension
       (MAX(1,LWORK))
	       On exit, if INFO = 0, WORK(1) returns the optimal LWORK.

       LWORK   (input) INTEGER
	       The length of the array	WORK.	LWORK  >=  max(1,3*N-1).   For
	       optimal	efficiency,  LWORK >= (NB+2)*N, where NB is the block‐
	       size for DSYTRD returned by ILAENV.  If	LWORK  =  -1,  then  a
	       workspace  query	 is  assumed;  the routine only calculates the
	       optimal size of the WORK array, returns this value as the first
	       entry  of the WORK array, and no error message related to LWORK
	       is issued by XERBLA.

       INFO    (output) INTEGER
	       = 0:  successful exit
	       < 0:  if INFO = -i, the i-th argument had an illegal value
	       > 0:  DPOTRF or DSYEV returned an error code:
	       <= N:  if INFO = i, DSYEV 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.

 LAPACK driver routine (version 3November 2008			      DSYGV(1)
[top]

List of man pages available for Scientific

Copyright (c) for man pages and the logo by the respective OS vendor.

For those who want to learn more, the polarhome community provides shell access and support.

[legal] [privacy] [GNU] [policy] [cookies] [netiquette] [sponsors] [FAQ]
Tweet
Polarhome, production since 1999.
Member of Polarhome portal.
Based on Fawad Halim's script.
....................................................................
Vote for polarhome
Free Shell Accounts :: the biggest list on the net