Provided by: liblapack-doc_3.3.1-1_all NAME

LAPACK-3  -  solves  for  the  N1  by  N2  matrix  X,  1  <=  N1,N2  <= 2, in   op(TL)*X +
ISGN*X*op(TR) = SCALE*B,

SYNOPSIS

SUBROUTINE DLASY2( LTRANL, LTRANR, ISGN, N1, N2, TL, LDTL, TR, LDTR,  B,  LDB,  SCALE,  X,
LDX, XNORM, INFO )

LOGICAL        LTRANL, LTRANR

INTEGER        INFO, ISGN, LDB, LDTL, LDTR, LDX, N1, N2

DOUBLE         PRECISION SCALE, XNORM

DOUBLE         PRECISION B( LDB, * ), TL( LDTL, * ), TR( LDTR, * ), X( LDX, * )

PURPOSE

DLASY2 solves for the N1 by N2 matrix X, 1 <= N1,N2 <= 2, in
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.

LAPACK auxiliary routine (version 3.2)     April 2011                            DLASY2(3lapack)