dgeqrt.f(3) [debian man page]

dgeqrt.f(3)							      LAPACK							       dgeqrt.f(3)

NAME

       dgeqrt.f -

SYNOPSIS

   Functions/Subroutines
       subroutine dgeqrt (M, N, NB, A, LDA, T, LDT, WORK, INFO)
	   DGEQRT

Function/Subroutine Documentation
   subroutine dgeqrt (integerM, integerN, integerNB, double precision, dimension( lda, * )A, integerLDA, double precision, dimension( ldt, * )T,
       integerLDT, double precision, dimension( * )WORK, integerINFO)
       DGEQRT

       Purpose:

	    DGEQRT computes a blocked QR factorization of a real M-by-N matrix A
	    using the compact WY representation of Q.

       Parameters:
	   M

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

	   N

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

	   NB

		     NB is INTEGER
		     The block size to be used in the blocked QR.  MIN(M,N) >= NB >= 1.

	   A

		     A is DOUBLE PRECISION array, dimension (LDA,N)
		     On entry, the M-by-N matrix A.
		     On exit, the elements on and above the diagonal of the array
		     contain the min(M,N)-by-N upper trapezoidal matrix R (R is
		     upper triangular if M >= N); the elements below the diagonal
		     are the columns of V.

	   LDA

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

	   T

		     T is DOUBLE PRECISION array, dimension (LDT,MIN(M,N))
		     The upper triangular block reflectors stored in compact form
		     as a sequence of upper triangular blocks.	See below
		     for further details.

	   LDT

		     LDT is INTEGER
		     The leading dimension of the array T.  LDT >= NB.

	   WORK

		     WORK is DOUBLE PRECISION array, dimension (NB*N)

	   INFO

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

       Author:
	   Univ. of Tennessee

	   Univ. of California Berkeley

	   Univ. of Colorado Denver

	   NAG Ltd.

       Date:
	   November 2011

       Further Details:

	     The matrix V stores the elementary reflectors H(i) in the i-th column
	     below the diagonal. For example, if M=5 and N=3, the matrix V is

			  V = (  1	 )
			      ( v1  1	 )
			      ( v1 v2  1 )
			      ( v1 v2 v3 )
			      ( v1 v2 v3 )

	     where the vi's represent the vectors which define H(i), which are returned
	     in the matrix A.  The 1's along the diagonal of V are not stored in A.

	     Let K=MIN(M,N).  The number of blocks is B = ceiling(K/NB), where each
	     block is of order NB except for the last block, which is of order
	     IB = K - (B-1)*NB.  For each of the B blocks, a upper triangular block
	     reflector factor is computed: T1, T2, ..., TB.  The NB-by-NB (and IB-by-IB
	     for the last block) T's are stored in the NB-by-N matrix T as

			  T = (T1 T2 ... TB).

       Definition at line 142 of file dgeqrt.f.

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

Version 3.4.1							  Sun May 26 2013						       dgeqrt.f(3)