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dorcsd2by1.f(3) LAPACK dorcsd2by1.f(3)

NAME

dorcsd2by1.f -

SYNOPSIS

Functions/Subroutines


subroutine dorcsd2by1 (JOBU1, JOBU2, JOBV1T, M, P, Q, X11, LDX11, X21, LDX21, THETA, U1, LDU1, U2, LDU2, V1T, LDV1T, WORK, LWORK, IWORK, INFO)
 
DORCSD2BY1

Function/Subroutine Documentation

subroutine dorcsd2by1 (characterJOBU1, characterJOBU2, characterJOBV1T, integerM, integerP, integerQ, double precision, dimension(ldx11,*)X11, integerLDX11, double precision, dimension(ldx21,*)X21, integerLDX21, double precision, dimension(*)THETA, double precision, dimension(ldu1,*)U1, integerLDU1, double precision, dimension(ldu2,*)U2, integerLDU2, double precision, dimension(ldv1t,*)V1T, integerLDV1T, double precision, dimension(*)WORK, integerLWORK, integer, dimension(*)IWORK, integerINFO)

DORCSD2BY1

Purpose: 

 Purpose:
 ========


 DORCSD2BY1 computes the CS decomposition of an M-by-Q matrix X with
 orthonormal columns that has been partitioned into a 2-by-1 block
 structure:


                                [  I  0  0 ]
                                [  0  C  0 ]
          [ X11 ]   [ U1 |    ] [  0  0  0 ]
      X = [-----] = [---------] [----------] V1**T .
          [ X21 ]   [    | U2 ] [  0  0  0 ]
                                [  0  S  0 ]
                                [  0  0  I ]
 
 X11 is P-by-Q. The orthogonal matrices U1, U2, V1, and V2 are P-by-P,
 (M-P)-by-(M-P), Q-by-Q, and (M-Q)-by-(M-Q), respectively. C and S are
 R-by-R nonnegative diagonal matrices satisfying C^2 + S^2 = I, in
 which R = MIN(P,M-P,Q,M-Q)..fi

 

Parameters:

JOBU1 

          JOBU1 is CHARACTER
           = 'Y':      U1 is computed;
           otherwise:  U1 is not computed.
JOBU2 
          JOBU2 is CHARACTER
           = 'Y':      U2 is computed;
           otherwise:  U2 is not computed.
JOBV1T 
          JOBV1T is CHARACTER
           = 'Y':      V1T is computed;
           otherwise:  V1T is not computed.
M 
          M is INTEGER
           The number of rows and columns in X.
P 
          P is INTEGER
           The number of rows in X11 and X12. 0 <= P <= M.
Q 
          Q is INTEGER
           The number of columns in X11 and X21. 0 <= Q <= M.
X11 
          X11 is DOUBLE PRECISION array, dimension (LDX11,Q)
           On entry, part of the orthogonal matrix whose CSD is
           desired.
LDX11 
          LDX11 is INTEGER
           The leading dimension of X11. LDX11 >= MAX(1,P).
X21 
          X21 is DOUBLE PRECISION array, dimension (LDX21,Q)
           On entry, part of the orthogonal matrix whose CSD is
           desired.
LDX21 
          LDX21 is INTEGER
           The leading dimension of X21. LDX21 >= MAX(1,M-P).
THETA 
          THETA is DOUBLE PRECISION array, dimension (R), in which R =
           MIN(P,M-P,Q,M-Q).
           C = DIAG( COS(THETA(1)), ... , COS(THETA(R)) ) and
           S = DIAG( SIN(THETA(1)), ... , SIN(THETA(R)) ).
U1 
          U1 is DOUBLE PRECISION array, dimension (P)
           If JOBU1 = 'Y', U1 contains the P-by-P orthogonal matrix U1.
LDU1 
          LDU1 is INTEGER
           The leading dimension of U1. If JOBU1 = 'Y', LDU1 >=
           MAX(1,P).
U2 
          U2 is DOUBLE PRECISION array, dimension (M-P)
           If JOBU2 = 'Y', U2 contains the (M-P)-by-(M-P) orthogonal
           matrix U2.
LDU2 
          LDU2 is INTEGER
           The leading dimension of U2. If JOBU2 = 'Y', LDU2 >=
           MAX(1,M-P).
V1T 
          V1T is DOUBLE PRECISION array, dimension (Q)
           If JOBV1T = 'Y', V1T contains the Q-by-Q matrix orthogonal
           matrix V1**T.
LDV1T 
          LDV1T is INTEGER
           The leading dimension of V1T. If JOBV1T = 'Y', LDV1T >=
           MAX(1,Q).
WORK 
          WORK is DOUBLE PRECISION array, dimension (MAX(1,LWORK))
           On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
           If INFO > 0 on exit, WORK(2:R) contains the values PHI(1),
           ..., PHI(R-1) that, together with THETA(1), ..., THETA(R),
           define the matrix in intermediate bidiagonal-block form
           remaining after nonconvergence. INFO specifies the number
           of nonzero PHI's.
LWORK 
          LWORK is INTEGER
           The dimension of the array WORK.

      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.
IWORK 
          IWORK is INTEGER array, dimension (M-MIN(P,M-P,Q,M-Q))
INFO 
          INFO is INTEGER
           = 0:  successful exit.
           < 0:  if INFO = -i, the i-th argument had an illegal value.
           > 0:  DBBCSD did not converge. See the description of WORK
                above for details.
Author:
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
July 2012
References:
[1] Brian D. Sutton. Computing the complete CS decomposition. Numer. Algorithms, 50(1):33-65, 2009.
Definition at line 236 of file dorcsd2by1.f.

Author

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