dtrsyl.f man page

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 (characterTRANA, characterTRANB, integerISGN, integerM, integerN, double precision, dimension( lda, * )A, integerLDA, double precision, dimension( ldb, * )B, integerLDB, double precision, dimension( ldc, * )C, integerLDC, double precisionSCALE, integerINFO)

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.

Date:

November 2011

Definition at line 164 of file dtrsyl.f.

Author

Generated automatically by Doxygen for LAPACK from the source code.

Referenced By

dtrsyl(3) is an alias of dtrsyl.f(3).

Sat Nov 16 2013 Version 3.4.2 LAPACK