NAME

       dlasy2.f -

SYNOPSIS

   Functions/Subroutines
       subroutine 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 (logicalLTRANL, logicalLTRANR, integerISGN, integerN1, integerN2, double
       precision, dimension( ldtl, * )TL, integerLDTL, double precision, dimension( ldtr, * )TR,
       integerLDTR, double precision, dimension( ldb, * )B, integerLDB, double precisionSCALE,
       double precision, dimension( ldx, * )X, integerLDX, double precisionXNORM, integerINFO)
       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:
           September 2012

       Definition at line 174 of file dlasy2.f.

Author

       Generated automatically by Doxygen for LAPACK from the source code.