slags2.f File Reference

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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.

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Function/Subroutine Documentation

subroutine slags2	(	logical	UPPER,
		real	A1,
		real	A2,
		real	A3,
		real	B1,
		real	B2,
		real	B3,
		real	CSU,
		real	SNU,
		real	CSV,
		real	SNV,
		real	CSQ,
		real	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.

Download SLAGS2 + dependencies [TGZ] [ZIP] [TXT]

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:

[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 REAL
[in]	A2	A2 is REAL
[in]	A3	A3 is REAL On entry, A1, A2 and A3 are elements of the input 2-by-2 upper (lower) triangular matrix A.
[in]	B1	B1 is REAL
[in]	B2	B2 is REAL
[in]	B3	B3 is REAL On entry, B1, B2 and B3 are elements of the input 2-by-2 upper (lower) triangular matrix B.
[out]	CSU	CSU is REAL
[out]	SNU	SNU is REAL The desired orthogonal matrix U.
[out]	CSV	CSV is REAL
[out]	SNV	SNV is REAL The desired orthogonal matrix V.
[out]	CSQ	CSQ is REAL
[out]	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.

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