?lasd0

Developer Reference for Intel® oneAPI Math Kernel Library for C

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ID 766684

Date 10/15/2026

Version

Public

?lasd0

Computes the singular values of a real upper bidiagonal n -by- m matrix B with diagonal d and off-diagonal e . Used by ?bdsdc .

Syntax

call slasd0(n, sqre, d, e, u, ldu, vt, ldvt, smlsiz, iwork, work, info)
call dlasd0(n, sqre, d, e, u, ldu, vt, ldvt, smlsiz, iwork, work, info)

void slasd0(lapack_int *n, lapack_int *sqre, float *d, float *e, float *u,
            lapack_int *ldu, float *vt, lapack_int *ldvt, lapack_int *smlsiz,
            lapack_int *iwork, float *work, lapack_int *info);

void dlasd0(lapack_int *n, lapack_int *sqre, double *d, double *e, double *u,
            lapack_int *ldu, double *vt, lapack_int *ldvt, lapack_int *smlsiz,
            lapack_int *iwork, double *work, lapack_int *info);

Include Files

mkl.h

Description

Using a divide and conquer approach, the routine ?lasd0 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 .

The related subroutine ?lasda (Computes the singular value decomposition (SVD) of a real upper bidiagonal matrix with diagonal d and off-diagonal e. Used by ?bdsdc.) computes only the singular values, and optionally, the singular vectors in compact form.

Input Parameters

n

On entry, the row dimension of the upper bidiagonal matrix. This is also the dimension of the main diagonal array d .

sqre

Specifies the column dimension of the bidiagonal matrix.

If sqre = 0 : the bidiagonal matrix has column dimension m = n . If sqre = 1 : the bidiagonal matrix has column dimension m = n+1 .

d: REAL for slasd0 DOUBLE PRECISION for dlasd0 Array, DIMENSION ( n ). On entry, d contains the main diagonal of the bidiagonal matrix.
e: REAL for slasd0 DOUBLE PRECISION for dlasd0 Array, DIMENSION ( m -1). Contains the subdiagonal entries of the bidiagonal matrix. On exit, e is destroyed.

ldu

On entry, leading dimension of the output array u .

ldvt

On entry, leading dimension of the output array vt .

smlsiz

On entry, maximum size of the subproblems at the bottom of the computation tree.

iwork: INTEGER . Workspace array, dimension must be at least (8n) .
work: REAL for slasd0 DOUBLE PRECISION for dlasd0 Workspace array, dimension must be at least (3m^{2}+2m) .

Output Parameters

d: On exit d , If info = 0 , contains singular values of the bidiagonal matrix.
u: REAL for slasd0 DOUBLE PRECISION for dlasd0 Array, DIMENSION at least ( ldq , n ). On exit, u contains the left singular vectors.
vt: REAL for slasd0 DOUBLE PRECISION for dlasd0 Array, DIMENSION at least ( ldvt , m ). On exit, vt^T contains the right singular vectors.

info

INTEGER .

If info = 0 : successful exit.
If info = -i < 0 , the i -th argument had an illegal value.
If info = 1 , a singular value did not converge.

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Developer Reference for Intel® oneAPI Math Kernel Library for C

?lasd0

Syntax

Include Files

Description

Input Parameters

Output Parameters