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clags2.f(3) | LAPACK | clags2.f(3) |
NAME¶
clags2.f -SYNOPSIS¶
Functions/Subroutines¶
subroutine clags2 (UPPER, A1, A2, A3, B1, B2, B3, CSU, SNU, CSV, SNV, CSQ, SNQ)
Function/Subroutine Documentation¶
subroutine clags2 (logicalUPPER, realA1, complexA2, realA3, realB1, complexB2, realB3, realCSU, complexSNU, realCSV, complexSNV, realCSQ, complexSNQ)¶
CLAGS2 Purpose:CLAGS2 computes 2-by-2 unitary matrices U, V and Q, such that if ( UPPER ) then U**H *A*Q = U**H *( A1 A2 )*Q = ( x 0 ) ( 0 A3 ) ( x x ) and V**H*B*Q = V**H *( B1 B2 )*Q = ( x 0 ) ( 0 B3 ) ( x x ) or if ( .NOT.UPPER ) then U**H *A*Q = U**H *( A1 0 )*Q = ( x x ) ( A2 A3 ) ( 0 x ) and V**H *B*Q = V**H *( B1 0 )*Q = ( x x ) ( B2 B3 ) ( 0 x ) where U = ( CSU SNU ), V = ( CSV SNV ), ( -SNU**H CSU ) ( -SNV**H CSV ) Q = ( CSQ SNQ ) ( -SNQ**H CSQ ) The rows of the transformed A and B are parallel. Moreover, if the input 2-by-2 matrix A is not zero, then the transformed (1,1) entry of A is not zero. If the input matrices A and B are both not zero, then the transformed (2,2) element of B is not zero, except when the first rows of input A and B are parallel and the second rows are zero.
UPPER
Author:
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 REALA2
A2 is COMPLEXA3
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 REALB2
B2 is COMPLEXB3
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 REALSNU
SNU is COMPLEX The desired unitary matrix U.CSV
CSV is REALSNV
SNV is COMPLEX The desired unitary matrix V.CSQ
CSQ is REALSNQ
SNQ is COMPLEX The desired unitary matrix Q.
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
November 2011
Definition at line 158 of file clags2.f.
Author¶
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