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

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

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 


Download CUNGTR + dependencies [TGZ] [ZIP] [TXT]
 CUNGTR generates a complex unitary matrix Q which is defined as the
 product of n-1 elementary reflectors of order N, as returned by

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

 if UPLO = 'L', Q = H(1) H(2) . . . H(n-1).
          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 is INTEGER
          The order of the matrix Q. N >= 0.
          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 is INTEGER
          The leading dimension of the array A. LDA >= N.
          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 is COMPLEX array, dimension (MAX(1,LWORK))
          On exit, if INFO = 0, WORK(1) returns the optimal 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 is INTEGER
          = 0:  successful exit
          < 0:  if INFO = -i, the i-th argument had an illegal value
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
November 2011

Definition at line 124 of file cungtr.f.

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