LAPACK  3.4.2
LAPACK: Linear Algebra PACKage
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cungql.f File Reference

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Functions/Subroutines

subroutine cungql (M, N, K, A, LDA, TAU, WORK, LWORK, INFO)
 CUNGQL

Function/Subroutine Documentation

subroutine cungql ( integer  M,
integer  N,
integer  K,
complex, dimension( lda, * )  A,
integer  LDA,
complex, dimension( * )  TAU,
complex, dimension( * )  WORK,
integer  LWORK,
integer  INFO 
)

CUNGQL

Download CUNGQL + dependencies [TGZ] [ZIP] [TXT]
Purpose: 
 CUNGQL generates an M-by-N complex matrix Q with orthonormal columns,
 which is defined as the last N columns of a product of K elementary
 reflectors of order M

       Q  =  H(k) . . . H(2) H(1)

 as returned by CGEQLF.
Parameters:
[in]M
          M is INTEGER
          The number of rows of the matrix Q. M >= 0.
[in]N
          N is INTEGER
          The number of columns of the matrix Q. M >= N >= 0.
[in]K
          K is INTEGER
          The number of elementary reflectors whose product defines the
          matrix Q. N >= K >= 0.
[in,out]A
          A is COMPLEX array, dimension (LDA,N)
          On entry, the (n-k+i)-th column must contain the vector which
          defines the elementary reflector H(i), for i = 1,2,...,k, as
          returned by CGEQLF in the last k columns of its array
          argument A.
          On exit, the M-by-N matrix Q.
[in]LDA
          LDA is INTEGER
          The first dimension of the array A. LDA >= max(1,M).
[in]TAU
          TAU is COMPLEX array, dimension (K)
          TAU(i) must contain the scalar factor of the elementary
          reflector H(i), as returned by CGEQLF.
[out]WORK
          WORK is COMPLEX array, dimension (MAX(1,LWORK))
          On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
[in]LWORK
          LWORK is INTEGER
          The dimension of the array WORK. LWORK >= max(1,N).
          For optimum performance LWORK >= N*NB, where NB is the
          optimal blocksize.

          If LWORK = -1, then a workspace query is assumed; the routine
          only calculates the optimal size of the WORK array, returns
          this value as the first entry of the WORK array, and no error
          message related to LWORK is issued by XERBLA.
[out]INFO
          INFO is INTEGER
          = 0:  successful exit
          < 0:  if INFO = -i, the i-th argument has an illegal value
Author:
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
November 2011

Definition at line 129 of file cungql.f.

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