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slags2.f(3) LAPACK 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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