# CentOS 7.0 - man page for dlasy2 (centos section 3)

dlasy2.f(3) LAPACK dlasy2.f(3)dlasy2.fNAME-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.SYNOPSISFunction/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 orop(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.-1.AuthorGenerated automatically by Doxygen for LAPACK from the source code.Version 3.4.2Tue Sep 25 2012 dlasy2.f(3)