zuncsd2by1.f - Man Page
SRC/zuncsd2by1.f
Synopsis
Functions/Subroutines
subroutine zuncsd2by1 (jobu1, jobu2, jobv1t, m, p, q, x11, ldx11, x21, ldx21, theta, u1, ldu1, u2, ldu2, v1t, ldv1t, work, lwork, rwork, lrwork, iwork, info)
ZUNCSD2BY1
Function/Subroutine Documentation
subroutine zuncsd2by1 (character jobu1, character jobu2, character jobv1t, integer m, integer p, integer q, complex*16, dimension(ldx11,*) x11, integer ldx11, complex*16, dimension(ldx21,*) x21, integer ldx21, double precision, dimension(*) theta, complex*16, dimension(ldu1,*) u1, integer ldu1, complex*16, dimension(ldu2,*) u2, integer ldu2, complex*16, dimension(ldv1t,*) v1t, integer ldv1t, complex*16, dimension(*) work, integer lwork, double precision, dimension(*) rwork, integer lrwork, integer, dimension(*) iwork, integer info)
ZUNCSD2BY1
Purpose:
ZUNCSD2BY1 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: [ I1 0 0 ] [ 0 C 0 ] [ X11 ] [ U1 | ] [ 0 0 0 ] X = [-----] = [---------] [----------] V1**T . [ X21 ] [ | U2 ] [ 0 0 0 ] [ 0 S 0 ] [ 0 0 I2] X11 is P-by-Q. The unitary matrices U1, U2, and V1 are P-by-P, (M-P)-by-(M-P), and Q-by-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). I1 is a K1-by-K1 identity matrix and I2 is a K2-by-K2 identity matrix, where K1 = MAX(Q+P-M,0), K2 = MAX(Q-P,0).
- 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 in X.
P
P is INTEGER The number of rows in X11. 0 <= P <= M.
Q
Q is INTEGER The number of columns in X11 and X21. 0 <= Q <= M.
X11
X11 is COMPLEX*16 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).
X21
X21 is COMPLEX*16 array, dimension (LDX21,Q) On entry, part of the unitary 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 COMPLEX*16 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*16 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*16 array, dimension (Q) If JOBV1T = 'Y', V1T contains the Q-by-Q matrix unitary matrix V1**T.
LDV1T
LDV1T is INTEGER The leading dimension of V1T. If JOBV1T = 'Y', LDV1T >= MAX(1,Q).
WORK
WORK is COMPLEX*16 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 and RWORK arrays, returns this value as the first entry of the WORK and RWORK array, respectively, and no error message related to LWORK or LRWORK is issued by XERBLA.
RWORK
RWORK is DOUBLE PRECISION 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 WORK and RWORK arrays, returns this value as the first entry of the WORK and RWORK array, respectively, and no error message related to LWORK or 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: ZBBCSD did not converge. See the description of WORK 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.
Definition at line 252 of file zuncsd2by1.f.
Author
Generated automatically by Doxygen for LAPACK from the source code.
Referenced By
The man page zuncsd2by1(3) is an alias of zuncsd2by1.f(3).
Tue Nov 28 2023 12:08:42 Version 3.12.0 LAPACK