cungtr.f man page

cungtr.f

Synopsis

Functions/Subroutines

subroutine cungtr (UPLO, N, A, LDA, TAU, WORK, LWORK, INFO)
CUNGTR

Function/Subroutine Documentation

subroutine cungtr (character UPLO, integer N, complex, dimension( lda, * ) A, integer LDA, complex, dimension( * ) TAU, complex, dimension( * ) WORK, integer LWORK, integer INFO)

CUNGTR  

Purpose:

 CUNGTR generates a complex unitary matrix Q which is defined as the
 product of n-1 elementary reflectors of order N, as returned by
 CHETRD:

 if UPLO = 'U', Q = H(n-1) . . . H(2) H(1),

 if UPLO = 'L', Q = H(1) H(2) . . . H(n-1).
Parameters:

UPLO

          UPLO is CHARACTER*1
          = 'U': Upper triangle of A contains elementary reflectors
                 from CHETRD;
          = 'L': Lower triangle of A contains elementary reflectors
                 from CHETRD.

N

          N is INTEGER
          The order of the matrix Q. N >= 0.

A

          A is COMPLEX array, dimension (LDA,N)
          On entry, the vectors which define the elementary reflectors,
          as returned by CHETRD.
          On exit, the N-by-N unitary matrix Q.

LDA

          LDA is INTEGER
          The leading dimension of the array A. LDA >= N.

TAU

          TAU is COMPLEX array, dimension (N-1)
          TAU(i) must contain the scalar factor of the elementary
          reflector H(i), as returned by CHETRD.

WORK

          WORK is COMPLEX array, dimension (MAX(1,LWORK))
          On exit, if INFO = 0, WORK(1) returns the optimal LWORK.

LWORK

          LWORK is INTEGER
          The dimension of the array WORK. LWORK >= N-1.
          For optimum performance LWORK >= (N-1)*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.

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:

December 2016

Definition at line 125 of file cungtr.f.

Author

Generated automatically by Doxygen for LAPACK from the source code.

Referenced By

The man page cungtr(3) is an alias of cungtr.f(3).

Tue Nov 14 2017 Version 3.8.0 LAPACK