Developer Reference for Intel® oneAPI Math Kernel Library for Fortran

ID 766686
Date 12/16/2022
Public

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?orcsd2by1/?uncsd2by1

Computes the CS decomposition of a block-partitioned orthogonal/unitary matrix.

Syntax

call sorcsd2by1( jobu1, jobu2, jobv1t, m, p, q, x11, ldx11, x21, ldx21, theta, u1, ldu1, u2, ldu2, v1t, ldv1t, work, lwork, iwork, info )

call dorcsd2by1( jobu1, jobu2, jobv1t, m, p, q, x11, ldx11, x21, ldx21, theta, u1, ldu1, u2, ldu2, v1t, ldv1t, work, lwork, iwork, info )

call cuncsd2by1( jobu1, jobu2, jobv1t, m, p, q, x11, ldx11, x21, ldx21, theta, u1, ldu1, u2, ldu2, v1t, ldv1t, work, lwork, rwork, lrwork, iwork, info )

call zuncsd2by1( jobu1, jobu2, jobv1t, m, p, q, x11, ldx11, x21, ldx21, theta, u1, ldu1, u2, ldu2, v1t, ldv1t, work, lwork, rwork, lrwork, iwork, info )

call orcsd2by1( x11,x21,theta,u1,u2,v1t[,jobu1][,jobu2][,jobv1t][,info] )

call uncsd2by1( x11,x21,theta,u1,u2,v1t[,jobu1][,jobu2][,jobv1t][,info] )

Include Files
  • mkl.fi, lapack.f90
Description

The routines ?orcsd2by1/?uncsd2by1 compute the CS decomposition of an m-by-q matrix X with orthonormal columns that has been partitioned into a 2-by-1 block structure:

Equation

x11 is p-by-q. The orthogonal/unitary matrices u1, u2, v1, and v2 are p-by-p, (m-p)-by-(m-p), q-by-q, (m-q)-by-(m-q), respectively. C and S are r-by-r nonnegative diagonal matrices satisfying C2 + S2 = I, in which r = min(p,m-p,q,m-q).

Input Parameters
jobu1

CHARACTER. If equal to 'Y', then u1 is computed. Otherwise, u1 is not computed.

jobu2

CHARACTER. If equal to 'Y', then u2 is computed. Otherwise, u2 is not computed.

jobv1t

CHARACTER. If equal to 'Y', then v1t is computed. Otherwise, v1t is not computed.

m

INTEGER. The number of rows and columns of the matrix X.

p

INTEGER. The number of rows in x11. 0 pm.

q

INTEGER. The number of columns in x11 . 0 qm.

x11

REAL for sorcsd2by1

DOUBLE PRECISION for dorcsd2by1

COMPLEX for cuncsd2by1

DOUBLE COMPLEX for zuncsd2by1

Array, size (ldx11,q).

On entry, the part of the orthogonal matrix whose CSD is desired.

ldx11

INTEGER. The leading dimension of the array x11. ldx11 max(1,p).

x21

REAL for sorcsd2by1

DOUBLE PRECISION for dorcsd2by1

COMPLEX for cuncsd2by1

DOUBLE COMPLEX for zuncsd2by1

Array, size (ldx21,q).

On entry, the part of the orthogonal matrix whose CSD is desired.

ldx21

INTEGER. The leading dimension of the array X. ldx21 max(1,m - p).

ldu1

INTEGER. The leading dimension of the array u1. If jobu1 = 'Y', ldu1 max(1,p).

ldu2

INTEGER. The leading dimension of the array u2. If jobu2 = 'Y', ldu2 max(1,m-p).

ldv1t

INTEGER. The leading dimension of the array v1t. If jobv1t = 'Y', ldv1t max(1,q).

work

REAL for sorcsd2by1

DOUBLE PRECISION for dorcsd2by1

COMPLEX for cuncsd2by1

DOUBLE COMPLEX for zuncsd2by1

Workspace array, size (max(1,lwork)).

lwork

INTEGER. The size of the work array. Constraints:

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

REAL for cuncsd2by1

DOUBLE PRECISION for zuncsd2by1

Workspace array, size (max(1,lrwork)).

lrwork

INTEGER. The size of the rwork array. Constraints:

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 rwork array, and no error message related to lrwork is issued by xerbla.

iwork

INTEGER. Workspace array, dimension m - min(p, m - p, q, m - q).

Output Parameters
theta

REAL for sorcsd2by1

DOUBLE PRECISION for dorcsd2by1

COMPLEX for cuncsd2by1

DOUBLE COMPLEX for zuncsd2by1

Array, size (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

REAL for sorcsd2by1

DOUBLE PRECISION for dorcsd2by1

COMPLEX for cuncsd2by1

DOUBLE COMPLEX for zuncsd2by1

Array, size (ldu1,p) .

If jobu1 = 'Y', u1 contains the p-by-p orthogonal/unitary matrix u1.

u2

REAL for sorcsd2by1

DOUBLE PRECISION for dorcsd2by1

COMPLEX for cuncsd2by1

DOUBLE COMPLEX for zuncsd2by1

Array, size (ldu2,m - p) .

If jobu2 = 'Y', u2 contains the (m-p)-by-(m-p) orthogonal/unitary matrix u2.

v1t

REAL for sorcsd2by1

DOUBLE PRECISION for dorcsd2by1

COMPLEX for cuncsd2by1

DOUBLE COMPLEX for zuncsd2by1

Array, size (ldv1t,q) .

If jobv1t = 'Y', v1t contains the q-by-q orthogonal matrix v1T or unitary matrix v1H.

work

On exit,

If info = 0,
work(1) returns the optimal lwork.
If info > 0,
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.
rwork

On exit,

If info = 0,
rwork(1) returns the optimal lrwork.
If info > 0,
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.
info

INTEGER.

= 0: successful exit

< 0: if info = -i, the i-th argument has an illegal value

> 0: ?orcsd2by1/?uncsd2by1 did not converge. See the description of work above for details.

Fortran 95 Interface Notes

Routines in Fortran 95 interface have fewer arguments in the calling sequence than their FORTRAN 77 counterparts. For general conventions applied to skip redundant or reconstructible arguments, see Fortran 95 Interface Conventions.

Specific details for the routine ?orcsd2by1/?orcsd2by1 interface are as follows:

x11

Holds the block of matrix X11 of size (p, q).

x21

Holds the block of matrix X21 of size (m-p, q).

theta

Holds the vector of length r = min(p,m-p,q,m-q).

u1

Holds the matrix u1 of size (p,p).

u2

Holds the matrix u2 of size (m-p,m-p).

v1t

Holds the matrix v1T or v1H of size (q,q).

jobu1

Indicates whether u1 is computed. Must be 'Y' or 'O'.

jobu2

Indicates whether u2 is computed. Must be 'Y' or 'O'.

jobv1t

Indicates whether v1t is computed. Must be 'Y' or 'O'.

See Also