NAME

       zunbdb5.f -

SYNOPSIS

   Functions/Subroutines
       subroutine zunbdb5 (M1, M2, N, X1, INCX1, X2, INCX2, Q1, LDQ1, Q2, LDQ2, WORK, LWORK,
           INFO)
           ZUNBDB5

Function/Subroutine Documentation

   subroutine zunbdb5 (integer M1, integer M2, integer N, complex*16, dimension(*) X1, integer
       INCX1, complex*16, dimension(*) X2, integer INCX2, complex*16, dimension(ldq1,*) Q1,
       integer LDQ1, complex*16, dimension(ldq2,*) Q2, integer LDQ2, complex*16, dimension(*)
       WORK, integer LWORK, integer INFO)
       ZUNBDB5

Purpose:

        ZUNBDB5 orthogonalizes the column vector
             X = [ X1 ]
                 [ X2 ]
        with respect to the columns of
             Q = [ Q1 ] .
                 [ Q2 ]
        The columns of Q must be orthonormal.

        If the projection is zero according to Kahan's "twice is enough"
        criterion, then some other vector from the orthogonal complement
        is returned. This vector is chosen in an arbitrary but deterministic
        way..fi

       Parameters:
           M1

                     M1 is INTEGER
                      The dimension of X1 and the number of rows in Q1. 0 <= M1.

           M2

                     M2 is INTEGER
                      The dimension of X2 and the number of rows in Q2. 0 <= M2.

           N

                     N is INTEGER
                      The number of columns in Q1 and Q2. 0 <= N.

           X1

                     X1 is COMPLEX*16 array, dimension (M1)
                      On entry, the top part of the vector to be orthogonalized.
                      On exit, the top part of the projected vector.

           INCX1

                     INCX1 is INTEGER
                      Increment for entries of X1.

           X2

                     X2 is COMPLEX*16 array, dimension (M2)
                      On entry, the bottom part of the vector to be
                      orthogonalized. On exit, the bottom part of the projected
                      vector.

           INCX2

                     INCX2 is INTEGER
                      Increment for entries of X2.

           Q1

                     Q1 is COMPLEX*16 array, dimension (LDQ1, N)
                      The top part of the orthonormal basis matrix.

           LDQ1

                     LDQ1 is INTEGER
                      The leading dimension of Q1. LDQ1 >= M1.

           Q2

                     Q2 is COMPLEX*16 array, dimension (LDQ2, N)
                      The bottom part of the orthonormal basis matrix.

           LDQ2

                     LDQ2 is INTEGER
                      The leading dimension of Q2. LDQ2 >= M2.

           WORK

                     WORK is COMPLEX*16 array, dimension (LWORK)

           LWORK

                     LWORK is INTEGER
                      The dimension of the array WORK. LWORK >= 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:
           July 2012

Author

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