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zgeqrt.f(3) LAPACK zgeqrt.f(3)

zgeqrt.f -


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

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.
Date:
November 2013
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 zgeqrt.f.

Generated automatically by Doxygen for LAPACK from the source code.
Sat Nov 16 2013 Version 3.4.2

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