SRC/dtrsyl.f(3)            Library Functions Manual            SRC/dtrsyl.f(3)

NAME
       SRC/dtrsyl.f

SYNOPSIS
   Functions/Subroutines
       subroutine dtrsyl (trana, tranb, isgn, m, n, a, lda, b, ldb, c, ldc,
           scale, info)
           DTRSYL

Function/Subroutine Documentation
   subroutine dtrsyl (character trana, character tranb, integer isgn, integer
       m, integer n, double precision, dimension( lda, * ) a, integer lda,
       double precision, dimension( ldb, * ) b, integer ldb, double precision,
       dimension( ldc, * ) c, integer ldc, double precision scale, integer
       info)
       DTRSYL

       Purpose:


            DTRSYL solves the real Sylvester matrix equation:

               op(A)*X + X*op(B) = scale*C or
               op(A)*X - X*op(B) = scale*C,

            where op(A) = A or A**T, and  A and B are both upper quasi-
            triangular. A is M-by-M and B is N-by-N; the right hand side C and
            the solution X are M-by-N; and scale is an output scale factor, set
            <= 1 to avoid overflow in X.

            A and B must be in Schur canonical form (as returned by DHSEQR), that
            is, block upper triangular with 1-by-1 and 2-by-2 diagonal blocks;
            each 2-by-2 diagonal block has its diagonal elements equal and its
            off-diagonal elements of opposite sign.

       Parameters
           TRANA

                     TRANA is CHARACTER*1
                     Specifies the option op(A):
                     = 'N': op(A) = A    (No transpose)
                     = 'T': op(A) = A**T (Transpose)
                     = 'C': op(A) = A**H (Conjugate transpose = Transpose)

           TRANB

                     TRANB is CHARACTER*1
                     Specifies the option op(B):
                     = 'N': op(B) = B    (No transpose)
                     = 'T': op(B) = B**T (Transpose)
                     = 'C': op(B) = B**H (Conjugate transpose = Transpose)

           ISGN

                     ISGN is INTEGER
                     Specifies the sign in the equation:
                     = +1: solve op(A)*X + X*op(B) = scale*C
                     = -1: solve op(A)*X - X*op(B) = scale*C

           M

                     M is INTEGER
                     The order of the matrix A, and the number of rows in the
                     matrices X and C. M >= 0.

           N

                     N is INTEGER
                     The order of the matrix B, and the number of columns in the
                     matrices X and C. N >= 0.

           A

                     A is DOUBLE PRECISION array, dimension (LDA,M)
                     The upper quasi-triangular matrix A, in Schur canonical form.

           LDA

                     LDA is INTEGER
                     The leading dimension of the array A. LDA >= max(1,M).

           B

                     B is DOUBLE PRECISION array, dimension (LDB,N)
                     The upper quasi-triangular matrix B, in Schur canonical form.

           LDB

                     LDB is INTEGER
                     The leading dimension of the array B. LDB >= max(1,N).

           C

                     C is DOUBLE PRECISION array, dimension (LDC,N)
                     On entry, the M-by-N right hand side matrix C.
                     On exit, C is overwritten by the solution matrix X.

           LDC

                     LDC is INTEGER
                     The leading dimension of the array C. LDC >= max(1,M)

           SCALE

                     SCALE is DOUBLE PRECISION
                     The scale factor, scale, set <= 1 to avoid overflow in X.

           INFO

                     INFO is INTEGER
                     = 0: successful exit
                     < 0: if INFO = -i, the i-th argument had an illegal value
                     = 1: A and B have common or very close eigenvalues; perturbed
                          values were used to solve the equation (but the matrices
                          A and B are unchanged).

       Author
           Univ. of Tennessee

           Univ. of California Berkeley

           Univ. of Colorado Denver

           NAG Ltd.

       Definition at line 162 of file dtrsyl.f.

Author
       Generated automatically by Doxygen for LAPACK from the source code.

LAPACK                          Version 3.12.0                 SRC/dtrsyl.f(3)