LAPACK 3.12.0
LAPACK: Linear Algebra PACKage
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◆ zgemqr()

subroutine zgemqr ( character  side,
character  trans,
integer  m,
integer  n,
integer  k,
complex*16, dimension( lda, * )  a,
integer  lda,
complex*16, dimension( * )  t,
integer  tsize,
complex*16, dimension( ldc, * )  c,
integer  ldc,
complex*16, dimension( * )  work,
integer  lwork,
integer  info 
)

ZGEMQR

Purpose:
 ZGEMQR overwrites the general real M-by-N matrix C with

                      SIDE = 'L'     SIDE = 'R'
      TRANS = 'N':      Q * C          C * Q
      TRANS = 'T':      Q**H * C       C * Q**H

 where Q is a complex unitary matrix defined as the product
 of blocked elementary reflectors computed by tall skinny
 QR factorization (ZGEQR)
Parameters
[in]SIDE
          SIDE is CHARACTER*1
          = 'L': apply Q or Q**H from the Left;
          = 'R': apply Q or Q**H from the Right.
[in]TRANS
          TRANS is CHARACTER*1
          = 'N':  No transpose, apply Q;
          = 'C':  Conjugate transpose, apply Q**H.
[in]M
          M is INTEGER
          The number of rows of the matrix A.  M >=0.
[in]N
          N is INTEGER
          The number of columns of the matrix C. N >= 0.
[in]K
          K is INTEGER
          The number of elementary reflectors whose product defines
          the matrix Q.
          If SIDE = 'L', M >= K >= 0;
          if SIDE = 'R', N >= K >= 0.
[in]A
          A is COMPLEX*16 array, dimension (LDA,K)
          Part of the data structure to represent Q as returned by ZGEQR.
[in]LDA
          LDA is INTEGER
          The leading dimension of the array A.
          If SIDE = 'L', LDA >= max(1,M);
          if SIDE = 'R', LDA >= max(1,N).
[in]T
          T is COMPLEX*16 array, dimension (MAX(5,TSIZE)).
          Part of the data structure to represent Q as returned by ZGEQR.
[in]TSIZE
          TSIZE is INTEGER
          The dimension of the array T. TSIZE >= 5.
[in,out]C
          C is COMPLEX*16 array, dimension (LDC,N)
          On entry, the M-by-N matrix C.
          On exit, C is overwritten by Q*C or Q**H*C or C*Q**H or C*Q.
[in]LDC
          LDC is INTEGER
          The leading dimension of the array C. LDC >= max(1,M).
[out]WORK
         (workspace) COMPLEX*16 array, dimension (MAX(1,LWORK))
[in]LWORK
          LWORK is INTEGER
          The dimension of the array WORK.
          If LWORK = -1, then a workspace query is assumed. The routine
          only calculates the size of the WORK array, returns this
          value as WORK(1), and no error message related to WORK
          is issued by XERBLA.
[out]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
 These details are particular for this LAPACK implementation. Users should not
 take them for granted. These details may change in the future, and are not likely
 true for another LAPACK implementation. These details are relevant if one wants
 to try to understand the code. They are not part of the interface.

 In this version,

          T(2): row block size (MB)
          T(3): column block size (NB)
          T(6:TSIZE): data structure needed for Q, computed by
                           ZLATSQR or ZGEQRT

  Depending on the matrix dimensions M and N, and row and column
  block sizes MB and NB returned by ILAENV, ZGEQR will use either
  ZLATSQR (if the matrix is tall-and-skinny) or ZGEQRT to compute
  the QR factorization.
  This version of ZGEMQR will use either ZLAMTSQR or ZGEMQRT to
  multiply matrix Q by another matrix.
  Further Details in ZLAMTSQR or ZGEMQRT.