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cuncsd.f(3)				      LAPACK				      cuncsd.f(3)

NAME
       cuncsd.f -

SYNOPSIS
   Functions/Subroutines
       recursive subroutine cuncsd (JOBU1, JOBU2, JOBV1T, JOBV2T, TRANS, SIGNS, M, P, Q, X11,
	   LDX11, X12, LDX12, X21, LDX21, X22, LDX22, THETA, U1, LDU1, U2, LDU2, V1T, LDV1T, V2T,
	   LDV2T, WORK, LWORK, RWORK, LRWORK, IWORK, INFO)
	   CUNCSD

Function/Subroutine Documentation
   recursive subroutine cuncsd (characterJOBU1, characterJOBU2, characterJOBV1T, characterJOBV2T,
       characterTRANS, characterSIGNS, integerM, integerP, integerQ, complex, dimension( ldx11, *
       )X11, integerLDX11, complex, dimension( ldx12, * )X12, integerLDX12, complex, dimension(
       ldx21, * )X21, integerLDX21, complex, dimension( ldx22,			       * )X22,
       integerLDX22, real, dimension( * )THETA, complex, dimension( ldu1, * )U1, integerLDU1,
       complex, dimension( ldu2, * )U2, integerLDU2, complex, dimension( ldv1t, * )V1T,
       integerLDV1T, complex, dimension( ldv2t, * )V2T, integerLDV2T, complex, dimension( *
       )WORK, integerLWORK, real, dimension( * )RWORK, integerLRWORK, integer, dimension( *
       )IWORK, integerINFO)
       CUNCSD

       Purpose:

	    CUNCSD computes the CS decomposition of an M-by-M partitioned
	    unitary matrix X:

					    [  I  0  0 |  0  0	0 ]
					    [  0  C  0 |  0 -S	0 ]
		[ X11 | X12 ]	[ U1 |	  ] [  0  0  0 |  0  0 -I ] [ V1 |    ]**H
	    X = [-----------] = [---------] [---------------------] [---------]   .
		[ X21 | X22 ]	[    | U2 ] [  0  0  0 |  I  0	0 ] [	 | V2 ]
					    [  0  S  0 |  0  C	0 ]
					    [  0  0  I |  0  0	0 ]

	    X11 is P-by-Q. The unitary 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).

       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.

	   JOBV2T

		     JOBV2T is CHARACTER
		     = 'Y':	 V2T is computed;
		     otherwise:  V2T is not computed.

	   TRANS

		     TRANS is CHARACTER
		     = 'T':	 X, U1, U2, V1T, and V2T are stored in row-major
				 order;
		     otherwise:  X, U1, U2, V1T, and V2T are stored in column-
				 major order.

	   SIGNS

		     SIGNS is CHARACTER
		     = 'O':	 The lower-left block is made nonpositive (the
				 "other" convention);
		     otherwise:  The upper-right block is made nonpositive (the
				 "default" convention).

	   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 COMPLEX array, dimension (LDX11,Q)
		     On entry, part of the unitary matrix whose CSD is desired.

	   LDX11

		     LDX11 is INTEGER
		     The leading dimension of X11. LDX11 >= MAX(1,P).

	   X12

		     X12 is COMPLEX array, dimension (LDX12,M-Q)
		     On entry, part of the unitary matrix whose CSD is desired.

	   LDX12

		     LDX12 is INTEGER
		     The leading dimension of X12. LDX12 >= MAX(1,P).

	   X21

		     X21 is COMPLEX array, dimension (LDX21,Q)
		     On entry, part of the unitary matrix whose CSD is desired.

	   LDX21

		     LDX21 is INTEGER
		     The leading dimension of X11. LDX21 >= MAX(1,M-P).

	   X22

		     X22 is COMPLEX array, dimension (LDX22,M-Q)
		     On entry, part of the unitary matrix whose CSD is desired.

	   LDX22

		     LDX22 is INTEGER
		     The leading dimension of X11. LDX22 >= MAX(1,M-P).

	   THETA

		     THETA is REAL 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 COMPLEX array, dimension (P)
		     If JOBU1 = 'Y', U1 contains the P-by-P unitary matrix U1.

	   LDU1

		     LDU1 is INTEGER
		     The leading dimension of U1. If JOBU1 = 'Y', LDU1 >=
		     MAX(1,P).

	   U2

		     U2 is COMPLEX array, dimension (M-P)
		     If JOBU2 = 'Y', U2 contains the (M-P)-by-(M-P) unitary
		     matrix U2.

	   LDU2

		     LDU2 is INTEGER
		     The leading dimension of U2. If JOBU2 = 'Y', LDU2 >=
		     MAX(1,M-P).

	   V1T

		     V1T is COMPLEX array, dimension (Q)
		     If JOBV1T = 'Y', V1T contains the Q-by-Q matrix unitary
		     matrix V1**H.

	   LDV1T

		     LDV1T is INTEGER
		     The leading dimension of V1T. If JOBV1T = 'Y', LDV1T >=
		     MAX(1,Q).

	   V2T

		     V2T is COMPLEX array, dimension (M-Q)
		     If JOBV2T = 'Y', V2T contains the (M-Q)-by-(M-Q) unitary
		     matrix V2**H.

	   LDV2T

		     LDV2T is INTEGER
		     The leading dimension of V2T. If JOBV2T = 'Y', LDV2T >=
		     MAX(1,M-Q).

	   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.

		     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.

	   RWORK

		     RWORK is REAL array, dimension MAX(1,LRWORK)
		     On exit, if INFO = 0, RWORK(1) returns the optimal LRWORK.
		     If INFO > 0 on exit, RWORK(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.

	   LRWORK

		     LRWORK is INTEGER
		     The dimension of the array RWORK.

		     If LRWORK = -1, then a workspace query is assumed; the routine
		     only calculates the optimal size of the RWORK array, returns
		     this value as the first entry of the work array, and no error
		     message related to LRWORK 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:  CBBCSD did not converge. See the description of RWORK
			   above for details.

       References:
	   [1] Brian D. Sutton. Computing the complete CS decomposition. Numer. Algorithms,
	   50(1):33-65, 2009.

       Author:
	   Univ. of Tennessee

	   Univ. of California Berkeley

	   Univ. of Colorado Denver

	   NAG Ltd.

       Date:
	   November 2011

       Definition at line 316 of file cuncsd.f.

Author
       Generated automatically by Doxygen for LAPACK from the source code.

Version 3.4.2				 Tue Sep 25 2012			      cuncsd.f(3)
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