Developer Reference for Intel® oneAPI Math Kernel Library for C
?bbcsd
Computes the CS decomposition of an orthogonal/unitary matrix in bidiagonal-block form.
Syntax
lapack_int LAPACKE_sbbcsd(int matrix_layout, char jobu1, char jobu2, char jobv1t,
char jobv2t, char trans, lapack_int m, lapack_int p,
lapack_int q, float *theta, float *phi, float *u1,
lapack_int ldu1, float *u2, lapack_int ldu2, float *v1t,
lapack_int ldv1t, float *v2t, lapack_int ldv2t, float *b11d,
float *b11e, float *b12d, float *b12e, float *b21d, float *b21e,
float *b22d, float *b22e);
lapack_int LAPACKE_dbbcsd(int matrix_layout, char jobu1, char jobu2, char jobv1t,
char jobv2t, char trans, lapack_int m, lapack_int p,
lapack_int q, double *theta, double *phi, double *u1,
lapack_int ldu1, double *u2, lapack_int ldu2, double *v1t,
lapack_int ldv1t, double *v2t, lapack_int ldv2t, double *b11d,
double *b11e, double *b12d, double *b12e, double *b21d,
double *b21e, double *b22d, double *b22e);
lapack_int LAPACKE_cbbcsd(int matrix_layout, char jobu1, char jobu2, char jobv1t,
char jobv2t, char trans, lapack_int m, lapack_int p,
lapack_int q, float *theta, float *phi,
lapack_complex_float *u1, lapack_int ldu1,
lapack_complex_float *u2, lapack_int ldu2,
lapack_complex_float *v1t, lapack_int ldv1t,
lapack_complex_float *v2t, lapack_int ldv2t, float *b11d,
float *b11e, float *b12d, float *b12e, float *b21d, float *b21e,
float *b22d, float *b22e);
lapack_int LAPACKE_zbbcsd(int matrix_layout, char jobu1, char jobu2, char jobv1t,
char jobv2t, char trans, lapack_int m, lapack_int p,
lapack_int q, double *theta, double *phi,
lapack_complex_double *u1, lapack_int ldu1,
lapack_complex_double *u2, lapack_int ldu2,
lapack_complex_double *v1t, lapack_int ldv1t,
lapack_complex_double *v2t, lapack_int ldv2t, double *b11d,
double *b11e, double *b12d, double *b12e, double *b21d,
double *b21e, double *b22d, double *b22e);Include Files
mkl.h
Description
mkl_lapack.fi The routine ?bbcsd computes the CS decomposition of an orthogonal or unitary matrix in bidiagonal-block form:
or
respectively.
x is m -by- m with the top-left block p -by- q . Note that q must not be larger than p , m - p , or m - q . If q is not the smallest index, x must be transposed and/or permuted in constant time using the trans option. See ?orcsd/?uncsd for details.
The bidiagonal matrices b11 , b12 , b21 , and b22 are represented implicitly by angles theta(1:q) and phi(1:q-1) .
The orthogonal/unitary matrices u1 , u2 , v1t , and v2t are input/output. The input matrices are pre- or post-multiplied by the appropriate singular vector matrices.
Input Parameters
- matrix_layout
-
Specifies whether matrix storage layout is row major ( LAPACK_ROW_MAJOR ) or column major ( LAPACK_COL_MAJOR ).
jobu1
If equals Y , then u1 is updated. Otherwise, u1 is not updated.
jobu2
If equals Y , then u2 is updated. Otherwise, u2 is not updated.
jobv1t
If equals Y , then v1t is updated. Otherwise, v1t is not updated.
jobv2t
If equals Y , then v2t is updated. Otherwise, v2t is not updated.
- trans
-
CHARACTER
m
The number of rows and columns of the orthogonal/unitary matrix X in bidiagonal-block form.
p
The number of rows in the top-left block of x . 0 ≤p≤m .
q
The number of columns in the top-left block of x . 0 q≤ min(p,m-p,m-q) .
- theta
-
REAL for sbbcsd DOUBLE PRECISION for dbbcsd COMPLEX for cbbcsd DOUBLE COMPLEX for zbbcsd
Array, size q .
On entry, the angles theta(1)[0] , …, theta(q)[q - 1] that, along with phi(1)[0] , …, phi(q-1)[q - 2] , define the matrix in bidiagonal-block form as returned by GUID-B830AE7B-F650-497E-B4F8-BB7E116650AE.xml .
- phi
-
REAL for sbbcsd DOUBLE PRECISION for dbbcsd COMPLEX for cbbcsd DOUBLE COMPLEX for zbbcsd
Array, size q -1 .
The angles phi(1)[0] , …, phi(q-1)[q - 2] that, along with theta(1)[0] , …, theta(q)[q - 1] , define the matrix in bidiagonal-block form as returned by GUID-B830AE7B-F650-497E-B4F8-BB7E116650AE.xml .
- u1
-
REAL for sbbcsd DOUBLE PRECISION for dbbcsd COMPLEX for cbbcsd DOUBLE COMPLEX for zbbcsd
Array, size at least max(1, ldu1 * p ) .
On entry, a p -by- p matrix.
ldu1
The leading dimension of the array u1 , ldu1 ≤ max(1, p ).
- u2
-
REAL for sbbcsd DOUBLE PRECISION for dbbcsd COMPLEX for cbbcsd DOUBLE COMPLEX for zbbcsd
Array, size max(1, ldu2 *( m - p )) .
On entry, an ( m - p )-by-( m - p ) matrix.
ldu2
The leading dimension of the array u2 , ldu2 ≤ max(1, m - p ).
- v1t
-
REAL for sbbcsd DOUBLE PRECISION for dbbcsd COMPLEX for cbbcsd DOUBLE COMPLEX for zbbcsd
Array, size max(1, ldv1t * q ) .
On entry, a q -by- q matrix.
ldv1t
The leading dimension of the array v1t , ldv1t ≤ max(1, q ).
- v2t
-
REAL for sbbcsd DOUBLE PRECISION for dbbcsd COMPLEX for cbbcsd DOUBLE COMPLEX for zbbcsd
Array, size .
On entry, an ( m - q )-by-( m - q ) matrix.
ldv2t
The leading dimension of the array v2t , ldv2t ≤ max(1, m - q ).
- work
-
REAL for sbbcsd DOUBLE PRECISION for dbbcsd COMPLEX for cbbcsd DOUBLE COMPLEX for zbbcsd Workspace array, size ( max(1,lwork) ).
lwork
The size of the work array. lwork? max(1,8*q)
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 .
Output Parameters
- theta
-
REAL for sbbcsd DOUBLE PRECISION for dbbcsd COMPLEX for cbbcsd DOUBLE COMPLEX for zbbcsd On exit, the angles whose cosines and sines define the diagonal blocks in the CS decomposition.
- u1
-
REAL for sbbcsd DOUBLE PRECISION for dbbcsd COMPLEX for cbbcsd DOUBLE COMPLEX for zbbcsd On exit, u1 is postmultiplied by the left singular vector matrix common to [ b11 ; 0 ] and [ b12 0 0 ; 0 -I 0 ] .
- u2
-
REAL for sbbcsd DOUBLE PRECISION for dbbcsd COMPLEX for cbbcsd DOUBLE COMPLEX for zbbcsd On exit, u2 is postmultiplied by the left singular vector matrix common to [ b21 ; 0 ] and [ b22 0 0 ; 0 0 I ] .
- v1t
-
REAL for sbbcsd DOUBLE PRECISION for dbbcsd COMPLEX for cbbcsd DOUBLE COMPLEX for zbbcsd
Array, size q .
On exit, v1t is premultiplied by the transpose of the right singular vector matrix common to [ b11 ; 0 ] and [ b21 ; 0 ] .
- v2t
-
REAL for sbbcsd DOUBLE PRECISION for dbbcsd COMPLEX for cbbcsd DOUBLE COMPLEX for zbbcsd On exit, v2t is premultiplied by the transpose of the right singular vector matrix common to [ b12 0 0 ; 0 -I 0 ] and [ b22 0 0 ; 0 0 I ] .
- b11d
-
REAL for sbbcsd DOUBLE PRECISION for dbbcsd COMPLEX for cbbcsd DOUBLE COMPLEX for zbbcsd
Array, size q .
When ?bbcsd converges, b11d contains the cosines of theta(1)[0] , …, theta(q)[q - 1] . If ?bbcsd fails to converge, b11d contains the diagonal of the partially reduced top left block.
- b11e
-
REAL for sbbcsd DOUBLE PRECISION for dbbcsd COMPLEX for cbbcsd DOUBLE COMPLEX for zbbcsd
Array, size q -1 .
When ?bbcsd converges, b11e contains zeros. If ?bbcsd fails to converge, b11e contains the superdiagonal of the partially reduced top left block.
- b12d
-
REAL for sbbcsd DOUBLE PRECISION for dbbcsd COMPLEX for cbbcsd DOUBLE COMPLEX for zbbcsd
Array, size q .
When ?bbcsd converges, b12d contains the negative sines of theta(1)[0] , …, theta(q)[q - 1] . If ?bbcsd fails to converge, b12d contains the diagonal of the partially reduced top right block.
- b12e
-
REAL for sbbcsd DOUBLE PRECISION for dbbcsd COMPLEX for cbbcsd DOUBLE COMPLEX for zbbcsd
Array, size q -1 .
When ?bbcsd converges, b12e contains zeros. If ?bbcsd fails to converge, b11e contains the superdiagonal of the partially reduced top right block.
Return Values
This function returns a value info .
If info=0 , the execution is successful.
If info = -i , the i -th parameter had an illegal value.
If info > 0 and if ?bbcsd did not converge, info specifies the number of nonzero entries in phi , and b11d , b11e , etc. contain the partially reduced matrix.
Fortran 95 Interface Notes
There exist FORTRAN 77 and FORTRAN 95 interfaces for this routine. See the Intel® oneMKL Fortran Developer Reference for details.