LAGS2 - 5.2 English - 68552

LAGS2 computes 2-by-2 orthogonal matrices U, V, and Q, and applies them

to matrices A and B such that the rows of the transformed A and B are parallel.

Purpose:

 LAGS2 computes 2-by-2 orthogonal matrices U, V and Q, such
 that if (UPPER) then

           U**T *A*Q = U**T *(A1 A2)*Q = (x  0 )
                             (0  A3)     (x  x )
 and
           V**T*B*Q = V**T *(B1 B2)*Q = (x  0 )
                            (0  B3)     (x  x )

 or if (.NOT.UPPER) then

           U**T *A*Q = U**T *(A1 0 )*Q = (x  x )
                             (A2 A3)     (0  x )
 and
           V**T*B*Q = V**T*(B1 0 )*Q = (x  x )
                           (B2 B3)     (0  x )

 The rows of the transformed A and B are parallel, where

   U = ( CSU  SNU), V = ( CSV SNV), Q = ( CSQ   SNQ)
       (-SNU  CSU)      (-SNV CSV)      (-SNQ   CSQ)

 Z**T denotes the transpose of Z.

Parameters:

• UPPER – [in]

  UPPER is LOGICAL

  = .TRUE.: the input matrices A and B are upper triangular.

  = .FALSE.: the input matrices A and B are lower triangular.

• A1 – [in] A1 is REAL

• A2 – [in] A2 is REAL

• A3 – [in]

  A3 is REAL

  On entry, A1, A2 and A3 are elements of the input 2-by-2 upper (lower) triangular matrix A.

• B1 – [in] B1 is REAL

• B2 – [in] B2 is REAL

• B3 – [in]

  B3 is REAL

  On entry, B1, B2 and B3 are elements of the input 2-by-2 upper (lower) triangular matrix B.

• CSU – [out] CSU is REAL

• SNU – [out]

  SNU is REAL

  The desired orthogonal matrix U.

• CSV – [out] CSV is REAL

• SNV – [out]

  SNV is REAL

  The desired orthogonal matrix V.

• CSQ – [out] CSQ is REAL

• SNQ – [out]

  SNQ is REAL

  The desired orthogonal matrix Q.