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template<typename T>
void lasd0(integer *n, integer *sqre, T *d, T *e, T *u, integer *ldu, T *vt, integer *ldvt, integer *smlsiz, integer *iwork, T *work, integer *info)# LASD0 computes the singular values of a real upper bidiagonal n-by-m
matrix B with diagonal d and off-diagonal e. Used by sbdsdc.
Purpose:
Using a divide and conquer approach, SLASD0 computes the singular value decomposition (SVD) of a real upper bidiagonal N-by-M matrix B with diagonal D and offdiagonal E, where M = N + SQRE. The algorithm computes orthogonal matrices U and VT such that B = U * S * VT. The singular values S are overwritten on D. A related subroutine, SLASDA, computes only the singular values, and optionally, the singular vectors in compact form.
- Parameters:
N – [in]
N is INTEGER
On entry, the row dimension of the upper bidiagonal matrix. This is also the dimension of the main diagonal array D.
SQRE – [in]
SQRE is INTEGER
Specifies the column dimension of the bidiagonal matrix.
= 0: The bidiagonal matrix has column dimension M = N;
= 1: The bidiagonal matrix has column dimension M = N+1;
D – [inout]
D is REAL array, dimension (N)
On entry D contains the main diagonal of the bidiagonal matrix.
On exit D, if INFO = 0, contains its singular values.E – [inout]
E is REAL array, dimension (M-1)
Contains the subdiagonal entries of the bidiagonal matrix. On exit, E has been destroyed.
U – [out]
U is REAL array, dimension (LDU, N)
On exit, U contains the left singular vectors.
LDU – [in]
LDU is INTEGER
On entry, leading dimension of U.
VT – [out]
VT is REAL array, dimension (LDVT, M)
On exit, VT**T contains the right singular vectors.
LDVT – [in]
LDVT is INTEGER
On entry, leading dimension of VT.
SMLSIZ – [in]
SMLSIZ is INTEGER
On entry, maximum size of the subproblems at the bottom of the computation tree.
IWORK – [out] IWORK is INTEGER array, dimension (8*N)
WORK – [out] WORK is REAL array, dimension (3*M**2+2*M)
INFO – [out]
INFO is INTEGER
= 0: successful exit.
< 0: if INFO = -i, the i-th argument had an illegal value.
> 0: if INFO = 1, a singular value did not converge