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

NAME

       LAPACK-3 - solves the real Sylvester matrix equation

SYNOPSIS

       SUBROUTINE STRSYL( TRANA, TRANB, ISGN, M, N, A, LDA, B, LDB, C, LDC, SCALE, INFO )

           CHARACTER      TRANA, TRANB

           INTEGER        INFO, ISGN, LDA, LDB, LDC, M, N

           REAL           SCALE

           REAL           A( LDA, * ), B( LDB, * ), C( LDC, * )

PURPOSE

       STRSYL 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 SHSEQR), 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.

ARGUMENTS

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

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

        A       (input) REAL array, dimension (LDA,M)
                The upper quasi-triangular matrix A, in Schur canonical form.

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

        B       (input) REAL array, dimension (LDB,N)
                The upper quasi-triangular matrix B, in Schur canonical form.

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

        C       (input/output) REAL 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     (input) INTEGER
                The leading dimension of the array C. LDC >= max(1,M)

        SCALE   (output) REAL
                The scale factor, scale, set <= 1 to avoid overflow in X.

        INFO    (output) 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).

 LAPACK routine (version 3.3.1)             April 2011                            STRSYL(3lapack)