SRC/zgeqrt.f(3)            Library Functions Manual            SRC/zgeqrt.f(3)

NAME
       SRC/zgeqrt.f

SYNOPSIS
   Functions/Subroutines
       subroutine zgeqrt (m, n, nb, a, lda, t, ldt, work, info)
           ZGEQRT

Function/Subroutine Documentation
   subroutine zgeqrt (integer m, integer n, integer nb, complex*16, dimension(
       lda, * ) a, integer lda, complex*16, dimension( ldt, * ) t, integer
       ldt, complex*16, dimension( * ) work, integer info)
       ZGEQRT

       Purpose:


           !>
           !> ZGEQRT computes a blocked QR factorization of a complex 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 COMPLEX*16 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 COMPLEX*16 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 COMPLEX*16 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.

       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-K matrix T as
           !>
           !>               T = (T1 T2 ... TB).
           !>

       Definition at line 140 of file zgeqrt.f.

Author
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LAPACK                          Version 3.12.0                 SRC/zgeqrt.f(3)