LAPACK
3.4.2
LAPACK: Linear Algebra PACKage

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Functions/Subroutines  
subroutine  dlags2 (UPPER, A1, A2, A3, B1, B2, B3, CSU, SNU, CSV, SNV, CSQ, SNQ) 
DLAGS2 computes 2by2 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. 
subroutine dlags2  (  logical  UPPER, 
double precision  A1,  
double precision  A2,  
double precision  A3,  
double precision  B1,  
double precision  B2,  
double precision  B3,  
double precision  CSU,  
double precision  SNU,  
double precision  CSV,  
double precision  SNV,  
double precision  CSQ,  
double precision  SNQ  
) 
DLAGS2 computes 2by2 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.
Download DLAGS2 + dependencies [TGZ] [ZIP] [TXT]DLAGS2 computes 2by2 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.
[in]  UPPER  UPPER is LOGICAL = .TRUE.: the input matrices A and B are upper triangular. = .FALSE.: the input matrices A and B are lower triangular. 
[in]  A1  A1 is DOUBLE PRECISION 
[in]  A2  A2 is DOUBLE PRECISION 
[in]  A3  A3 is DOUBLE PRECISION On entry, A1, A2 and A3 are elements of the input 2by2 upper (lower) triangular matrix A. 
[in]  B1  B1 is DOUBLE PRECISION 
[in]  B2  B2 is DOUBLE PRECISION 
[in]  B3  B3 is DOUBLE PRECISION On entry, B1, B2 and B3 are elements of the input 2by2 upper (lower) triangular matrix B. 
[out]  CSU  CSU is DOUBLE PRECISION 
[out]  SNU  SNU is DOUBLE PRECISION The desired orthogonal matrix U. 
[out]  CSV  CSV is DOUBLE PRECISION 
[out]  SNV  SNV is DOUBLE PRECISION The desired orthogonal matrix V. 
[out]  CSQ  CSQ is DOUBLE PRECISION 
[out]  SNQ  SNQ is DOUBLE PRECISION The desired orthogonal matrix Q. 
Definition at line 152 of file dlags2.f.