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CentOS 7.0 - man page for dgesvd.f (centos section 3)

dgesvd.f(3)				      LAPACK				      dgesvd.f(3)

NAME
       dgesvd.f -

SYNOPSIS
   Functions/Subroutines
       subroutine dgesvd (JOBU, JOBVT, M, N, A, LDA, S, U, LDU, VT, LDVT, WORK, LWORK, INFO)
	    DGESVD computes the singular value decomposition (SVD) for GE matrices

Function/Subroutine Documentation
   subroutine dgesvd (characterJOBU, characterJOBVT, integerM, integerN, double precision,
       dimension( lda, * )A, integerLDA, double precision, dimension( * )S, double precision,
       dimension( ldu, * )U, integerLDU, double precision, dimension( ldvt, * )VT, integerLDVT,
       double precision, dimension( * )WORK, integerLWORK, integerINFO)
	DGESVD computes the singular value decomposition (SVD) for GE matrices

       Purpose:

	    DGESVD computes the singular value decomposition (SVD) of a real
	    M-by-N matrix A, optionally computing the left and/or right singular
	    vectors. The SVD is written

		 A = U * SIGMA * transpose(V)

	    where SIGMA is an M-by-N matrix which is zero except for its
	    min(m,n) diagonal elements, U is an M-by-M orthogonal matrix, and
	    V is an N-by-N orthogonal matrix.  The diagonal elements of SIGMA
	    are the singular values of A; they are real and non-negative, and
	    are returned in descending order.  The first min(m,n) columns of
	    U and V are the left and right singular vectors of A.

	    Note that the routine returns V**T, not V.

       Parameters:
	   JOBU

		     JOBU is CHARACTER*1
		     Specifies options for computing all or part of the matrix U:
		     = 'A':  all M columns of U are returned in array U:
		     = 'S':  the first min(m,n) columns of U (the left singular
			     vectors) are returned in the array U;
		     = 'O':  the first min(m,n) columns of U (the left singular
			     vectors) are overwritten on the array A;
		     = 'N':  no columns of U (no left singular vectors) are
			     computed.

	   JOBVT

		     JOBVT is CHARACTER*1
		     Specifies options for computing all or part of the matrix
		     V**T:
		     = 'A':  all N rows of V**T are returned in the array VT;
		     = 'S':  the first min(m,n) rows of V**T (the right singular
			     vectors) are returned in the array VT;
		     = 'O':  the first min(m,n) rows of V**T (the right singular
			     vectors) are overwritten on the array A;
		     = 'N':  no rows of V**T (no right singular vectors) are
			     computed.

		     JOBVT and JOBU cannot both be 'O'.

	   M

		     M is INTEGER
		     The number of rows of the input matrix A.	M >= 0.

	   N

		     N is INTEGER
		     The number of columns of the input matrix A.  N >= 0.

	   A

		     A is DOUBLE PRECISION array, dimension (LDA,N)
		     On entry, the M-by-N matrix A.
		     On exit,
		     if JOBU = 'O',  A is overwritten with the first min(m,n)
				     columns of U (the left singular vectors,
				     stored columnwise);
		     if JOBVT = 'O', A is overwritten with the first min(m,n)
				     rows of V**T (the right singular vectors,
				     stored rowwise);
		     if JOBU .ne. 'O' and JOBVT .ne. 'O', the contents of A
				     are destroyed.

	   LDA

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

	   S

		     S is DOUBLE PRECISION array, dimension (min(M,N))
		     The singular values of A, sorted so that S(i) >= S(i+1).

	   U

		     U is DOUBLE PRECISION array, dimension (LDU,UCOL)
		     (LDU,M) if JOBU = 'A' or (LDU,min(M,N)) if JOBU = 'S'.
		     If JOBU = 'A', U contains the M-by-M orthogonal matrix U;
		     if JOBU = 'S', U contains the first min(m,n) columns of U
		     (the left singular vectors, stored columnwise);
		     if JOBU = 'N' or 'O', U is not referenced.

	   LDU

		     LDU is INTEGER
		     The leading dimension of the array U.  LDU >= 1; if
		     JOBU = 'S' or 'A', LDU >= M.

	   VT

		     VT is DOUBLE PRECISION array, dimension (LDVT,N)
		     If JOBVT = 'A', VT contains the N-by-N orthogonal matrix
		     V**T;
		     if JOBVT = 'S', VT contains the first min(m,n) rows of
		     V**T (the right singular vectors, stored rowwise);
		     if JOBVT = 'N' or 'O', VT is not referenced.

	   LDVT

		     LDVT is INTEGER
		     The leading dimension of the array VT.  LDVT >= 1; if
		     JOBVT = 'A', LDVT >= N; if JOBVT = 'S', LDVT >= min(M,N).

	   WORK

		     WORK is DOUBLE PRECISION array, dimension (MAX(1,LWORK))
		     On exit, if INFO = 0, WORK(1) returns the optimal LWORK;
		     if INFO > 0, WORK(2:MIN(M,N)) contains the unconverged
		     superdiagonal elements of an upper bidiagonal matrix B
		     whose diagonal is in S (not necessarily sorted). B
		     satisfies A = U * B * VT, so it has the same singular values
		     as A, and singular vectors related by U and VT.

	   LWORK

		     LWORK is INTEGER
		     The dimension of the array WORK.
		     LWORK >= MAX(1,5*MIN(M,N)) for the paths (see comments inside code):
			- PATH 1  (M much larger than N, JOBU='N')
			- PATH 1t (N much larger than M, JOBVT='N')
		     LWORK >= MAX(1,3*MIN(M,N)+MAX(M,N),5*MIN(M,N)) for the other paths
		     For good performance, LWORK should generally be larger.

		     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

		     INFO is INTEGER
		     = 0:  successful exit.
		     < 0:  if INFO = -i, the i-th argument had an illegal value.
		     > 0:  if DBDSQR did not converge, INFO specifies how many
			   superdiagonals of an intermediate bidiagonal form B
			   did not converge to zero. See the description of WORK
			   above for details.

       Author:
	   Univ. of Tennessee

	   Univ. of California Berkeley

	   Univ. of Colorado Denver

	   NAG Ltd.

       Date:
	   April 2012

       Definition at line 211 of file dgesvd.f.

Author
       Generated automatically by Doxygen for LAPACK from the source code.

Version 3.4.2				 Tue Sep 25 2012			      dgesvd.f(3)


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