DLAGS2 (3)  Linux Manuals
NAME
dlags2.f 
SYNOPSIS
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.
Function/Subroutine Documentation
subroutine dlags2 (logicalUPPER, double precisionA1, double precisionA2, double precisionA3, double precisionB1, double precisionB2, double precisionB3, double precisionCSU, double precisionSNU, double precisionCSV, double precisionSNV, double precisionCSQ, double precisionSNQ)
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.
Purpose:

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.
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.
A1A1 is DOUBLE PRECISION
A2A2 is DOUBLE PRECISION
A3A3 is DOUBLE PRECISION On entry, A1, A2 and A3 are elements of the input 2by2 upper (lower) triangular matrix A.
B1B1 is DOUBLE PRECISION
B2B2 is DOUBLE PRECISION
B3B3 is DOUBLE PRECISION On entry, B1, B2 and B3 are elements of the input 2by2 upper (lower) triangular matrix B.
CSUCSU is DOUBLE PRECISION
SNUSNU is DOUBLE PRECISION The desired orthogonal matrix U.
CSVCSV is DOUBLE PRECISION
SNVSNV is DOUBLE PRECISION The desired orthogonal matrix V.
CSQCSQ is DOUBLE PRECISION
SNQSNQ is DOUBLE PRECISION 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 dlags2.f.
Author
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