LAPACK 3.11.0
LAPACK: Linear Algebra PACKage

◆ dorbdb5()

subroutine dorbdb5 ( integer  M1,
integer  M2,
integer  N,
double precision, dimension(*)  X1,
integer  INCX1,
double precision, dimension(*)  X2,
integer  INCX2,
double precision, dimension(ldq1,*)  Q1,
integer  LDQ1,
double precision, dimension(ldq2,*)  Q2,
integer  LDQ2,
double precision, dimension(*)  WORK,
integer  LWORK,
integer  INFO 
)

DORBDB5

Download DORBDB5 + dependencies [TGZ] [ZIP] [TXT]

Purpose:
 DORBDB5 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.
Parameters
[in]M1
          M1 is INTEGER
           The dimension of X1 and the number of rows in Q1. 0 <= M1.
[in]M2
          M2 is INTEGER
           The dimension of X2 and the number of rows in Q2. 0 <= M2.
[in]N
          N is INTEGER
           The number of columns in Q1 and Q2. 0 <= N.
[in,out]X1
          X1 is DOUBLE PRECISION array, dimension (M1)
           On entry, the top part of the vector to be orthogonalized.
           On exit, the top part of the projected vector.
[in]INCX1
          INCX1 is INTEGER
           Increment for entries of X1.
[in,out]X2
          X2 is DOUBLE PRECISION array, dimension (M2)
           On entry, the bottom part of the vector to be
           orthogonalized. On exit, the bottom part of the projected
           vector.
[in]INCX2
          INCX2 is INTEGER
           Increment for entries of X2.
[in]Q1
          Q1 is DOUBLE PRECISION array, dimension (LDQ1, N)
           The top part of the orthonormal basis matrix.
[in]LDQ1
          LDQ1 is INTEGER
           The leading dimension of Q1. LDQ1 >= M1.
[in]Q2
          Q2 is DOUBLE PRECISION array, dimension (LDQ2, N)
           The bottom part of the orthonormal basis matrix.
[in]LDQ2
          LDQ2 is INTEGER
           The leading dimension of Q2. LDQ2 >= M2.
[out]WORK
          WORK is DOUBLE PRECISION array, dimension (LWORK)
[in]LWORK
          LWORK is INTEGER
           The dimension of the array WORK. LWORK >= N.
[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.