SLAGS2 (3) Linux Manual Page

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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