LASV2 - 5.2 English - 68552

AOCL API Guide (68552)

Document ID
68552
Release Date
2025-12-29
Version
5.2 English
template<typename T>
void lasv2(T *f, T *g, T *h, T *ssmin, T *ssmax, T *snr, T *csr, T *snl, T *csl)#

LASV2 computes the singular value decomposition of a 2-by-2 triangular matrix.

Purpose:

 LASV2 computes the singular value decomposition of a 2-by-2
 triangular matrix
    [  F   G  ]
    [  0   H  ].
 On   return, abs(SSMAX) is the larger singular value, abs(SSMIN) is the
 smaller singular value, and (CSL,SNL) and (CSR,SNR) are the left and
 right singular vectors for abs(SSMAX), giving the decomposition

    [ CSL  SNL ] [  F   G  ] [ CSR -SNR ]  =  [ SSMAX   0   ]
    [-SNL  CSL ] [  0   H  ] [ SNR  CSR ]     [  0    SSMIN ].
Parameters:
  • F[in]

    F is REAL

    The (1,1) element of the 2-by-2 matrix.

  • G[in]

    G is REAL

    The (1,2) element of the 2-by-2 matrix.

  • H[in]

    H is REAL

    The (2,2) element of the 2-by-2 matrix.

  • SSMIN[out]

    SSMIN is REAL

    abs(SSMIN) is the smaller singular value.

  • SSMAX[out]

    SSMAX is REAL

    abs(SSMAX) is the larger singular value.

  • SNL[out] SNL is REAL

  • CSL[out]

    CSL is REAL

    The vector (CSL, SNL) is a unit left singular vector for the singular value abs(SSMAX).

  • SNR[out] SNR is REAL

  • CSR[out]

    CSR is REAL

    The vector (CSR, SNR) is a unit right singular vector for the singular value abs(SSMAX).