dlasy2.f - Online Linux Manual Page
Section : 3
Updated : Tue Nov 14 2017
Source : Version 3.8.0
Note : LAPACK
NAMEdlasy2.f
SYNOPSIS
Functions/Subroutinessubroutine dlasy2 (LTRANL, LTRANR, ISGN, N1, N2, TL, LDTL, TR, LDTR, B, LDB, SCALE, X, LDX, XNORM, INFO)
DLASY2 solves the Sylvester matrix equation where the matrices are of order 1 or 2.
Function/Subroutine Documentation
subroutine dlasy2 (logical LTRANL, logical LTRANR, integer ISGN, integer N1, integer N2, double precision, dimension( ldtl, * ) TL, integer LDTL, double precision, dimension( ldtr, * ) TR, integer LDTR, double precision, dimension( ldb, * ) B, integer LDB, double precision SCALE, double precision, dimension( ldx, * ) X, integer LDX, double precision XNORM, integer INFO)DLASY2 solves the Sylvester matrix equation where the matrices are of order 1 or 2. Purpose: DLASY2 solves for the N1 by N2 matrix X, 1 <= N1,N2 <= 2, in
op(TL)*X + ISGN*X*op(TR) = SCALE*B,
where TL is N1 by N1, TR is N2 by N2, B is N1 by N2, and ISGN = 1 or
-1. op(T) = T or T**T, where T**T denotes the transpose of T.Parameters: LTRANL LTRANL is LOGICAL
On entry, LTRANL specifies the op(TL):
= .FALSE., op(TL) = TL,
= .TRUE., op(TL) = TL**T.
LTRANR LTRANR is LOGICAL
On entry, LTRANR specifies the op(TR):
= .FALSE., op(TR) = TR,
= .TRUE., op(TR) = TR**T.
ISGN ISGN is INTEGER
On entry, ISGN specifies the sign of the equation
as described before. ISGN may only be 1 or -1.
N1 N1 is INTEGER
On entry, N1 specifies the order of matrix TL.
N1 may only be 0, 1 or 2.
N2 N2 is INTEGER
On entry, N2 specifies the order of matrix TR.
N2 may only be 0, 1 or 2.
TL TL is DOUBLE PRECISION array, dimension (LDTL,2)
On entry, TL contains an N1 by N1 matrix.
LDTL LDTL is INTEGER
The leading dimension of the matrix TL. LDTL >= max(1,N1).
TR TR is DOUBLE PRECISION array, dimension (LDTR,2)
On entry, TR contains an N2 by N2 matrix.
LDTR LDTR is INTEGER
The leading dimension of the matrix TR. LDTR >= max(1,N2).
B B is DOUBLE PRECISION array, dimension (LDB,2)
On entry, the N1 by N2 matrix B contains the right-hand
side of the equation.
LDB LDB is INTEGER
The leading dimension of the matrix B. LDB >= max(1,N1).
SCALE SCALE is DOUBLE PRECISION
On exit, SCALE contains the scale factor. SCALE is chosen
less than or equal to 1 to prevent the solution overflowing.
X X is DOUBLE PRECISION array, dimension (LDX,2)
On exit, X contains the N1 by N2 solution.
LDX LDX is INTEGER
The leading dimension of the matrix X. LDX >= max(1,N1).
XNORM XNORM is DOUBLE PRECISION
On exit, XNORM is the infinity-norm of the solution.
INFO INFO is INTEGER
On exit, INFO is set to
0: successful exit.
1: TL and TR have too close eigenvalues, so TL or
TR is perturbed to get a nonsingular equation.
NOTE: In the interests of speed, this routine does not
check the inputs for errors.Author: Univ. of Tennessee Univ. of California Berkeley Univ. of Colorado Denver NAG Ltd. Date: June 2016 Definition at line 176 of file dlasy2.f.
AuthorGenerated automatically by Doxygen for LAPACK from the source code. 0
Johanes Gumabo
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