SLASY2 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.

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 REAL 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 REAL 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 REAL 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 REAL


          On exit, SCALE contains the scale factor. SCALE is chosen


          less than or equal to 1 to prevent the solution overflowing.

X

          X is REAL 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 REAL


          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.

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

September 2012