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

       dgeqrt.f -

       subroutine dgeqrt (M, N, NB, A, LDA, T, LDT, WORK, INFO)

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


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


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


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


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


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


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


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

	   Univ. of Tennessee

	   Univ. of California Berkeley

	   Univ. of Colorado Denver

	   NAG Ltd.

	   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.

       Generated automatically by Doxygen for LAPACK from the source code.

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