DLASY2
November 2006
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.
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.
Arguments
| LTRANL |
(input) LOGICAL
On entry, LTRANL specifies the op(TL):
= .FALSE., op(TL) = TL, = .TRUE., op(TL) = TL**T. |
| LTRANR |
(input) LOGICAL
On entry, LTRANR specifies the op(TR):
= .FALSE., op(TR) = TR, = .TRUE., op(TR) = TR**T. |
| ISGN |
(input) INTEGER
On entry, ISGN specifies the sign of the equation
as described before. ISGN may only be 1 or -1. |
| N1 |
(input) INTEGER
On entry, N1 specifies the order of matrix TL.
N1 may only be 0, 1 or 2. |
| N2 |
(input) INTEGER
On entry, N2 specifies the order of matrix TR.
N2 may only be 0, 1 or 2. |
| TL |
(input) DOUBLE PRECISION array, dimension (LDTL,2)
On entry, TL contains an N1 by N1 matrix.
|
| LDTL |
(input) INTEGER
The leading dimension of the matrix TL. LDTL >= max(1,N1).
|
| TR |
(input) DOUBLE PRECISION array, dimension (LDTR,2)
On entry, TR contains an N2 by N2 matrix.
|
| LDTR |
(input) INTEGER
The leading dimension of the matrix TR. LDTR >= max(1,N2).
|
| B |
(input) DOUBLE PRECISION array, dimension (LDB,2)
On entry, the N1 by N2 matrix B contains the right-hand
side of the equation. |
| LDB |
(input) INTEGER
The leading dimension of the matrix B. LDB >= max(1,N1).
|
| SCALE |
(output) DOUBLE PRECISION
On exit, SCALE contains the scale factor. SCALE is chosen
less than or equal to 1 to prevent the solution overflowing. |
| X |
(output) DOUBLE PRECISION array, dimension (LDX,2)
On exit, X contains the N1 by N2 solution.
|
| LDX |
(input) INTEGER
The leading dimension of the matrix X. LDX >= max(1,N1).
|
| XNORM |
(output) DOUBLE PRECISION
On exit, XNORM is the infinity-norm of the solution.
|
| INFO |
(output) 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. |