slags2.f(3)

NAME
slags2.f -

SYNOPSIS

  Functions/Subroutines

subroutine slags2 (UPPER, A1, A2, A3, B1, B2, B3, CSU, SNU, CSV, SNV, CSQ, SNQ)
SLAGS2 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.

Function/Subroutine Documentation

  subroutine slags2 (logicalUPPER, realA1, realA2, realA3, realB1, realB2, realB3, realCSU, realSNU, realCSV, realSNV, realCSQ, realSNQ)

SLAGS2 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:

     SLAGS2 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

              UPPER is LOGICAL
              = .TRUE.: the input matrices A and B are upper triangular.
              = .FALSE.: the input matrices A and B are lower triangular.

    A1

              A1 is REAL

    A2

              A2 is REAL

    A3

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

    B1

              B1 is REAL

    B2

              B2 is REAL

    B3

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

    CSU

              CSU is REAL

    SNU

              SNU is REAL
              The desired orthogonal matrix U.

    CSV

              CSV is REAL

    SNV

              SNV is REAL
              The desired orthogonal matrix V.

    CSQ

              CSQ is REAL

    SNQ

              SNQ is REAL
              The desired orthogonal matrix Q.

Author:
    Univ. of Tennessee

    Univ. of California Berkeley

    Univ. of Colorado Denver

    NAG Ltd.

Date:
    September 2012

Definition at line 152 of file slags2.f.

Author

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