dlasy2 (l)  Linux Man Pages
dlasy2: solves for the N1 by N2 matrix X, 1 <= N1,N2 <= 2, in op(TL)*X + ISGN*X*op(TR) = SCALE*B,
Command to display dlasy2
manual in Linux: $ man l dlasy2
NAME
DLASY2  solves for the N1 by N2 matrix X, 1 <= N1,N2 <= 2, in op(TL)*X + ISGN*X*op(TR) = SCALE*B,
SYNOPSIS
 SUBROUTINE DLASY2(

LTRANL, LTRANR, ISGN, N1, N2, TL, LDTL, TR,
LDTR, B, LDB, SCALE, X, LDX, XNORM, INFO )

LOGICAL
LTRANL, LTRANR

INTEGER
INFO, ISGN, LDB, LDTL, LDTR, LDX, N1, N2

DOUBLE
PRECISION SCALE, XNORM

DOUBLE
PRECISION B( LDB, * ), TL( LDTL, * ), TR( LDTR, * ),
X( LDX, * )
PURPOSE
DLASY2 solves for the N1 by N2 matrix X, 1 <= N1,N2 <= 2, in
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 Taq, where Taq denotes the transpose of T.
ARGUMENTS
 LTRANL (input) LOGICAL

On entry, LTRANL specifies the op(TL):
= .FALSE., op(TL) = TL,
= .TRUE., op(TL) = TLaq.
 LTRANR (input) LOGICAL

On entry, LTRANR specifies the op(TR):
= .FALSE., op(TR) = TR,
= .TRUE., op(TR) = TRaq.
 ISGN (input) INTEGER

On entry, ISGN specifies the sign of the equation
as described before. ISGN may only be 1 or 1.
 N1 (input) INTEGER

On entry, N1 specifies the order of matrix TL.
N1 may only be 0, 1 or 2.
 N2 (input) INTEGER

On entry, N2 specifies the order of matrix TR.
N2 may only be 0, 1 or 2.
 TL (input) DOUBLE PRECISION array, dimension (LDTL,2)

On entry, TL contains an N1 by N1 matrix.
 LDTL (input) INTEGER

The leading dimension of the matrix TL. LDTL >= max(1,N1).
 TR (input) DOUBLE PRECISION array, dimension (LDTR,2)

On entry, TR contains an N2 by N2 matrix.
 LDTR (input) INTEGER

The leading dimension of the matrix TR. LDTR >= max(1,N2).
 B (input) DOUBLE PRECISION array, dimension (LDB,2)

On entry, the N1 by N2 matrix B contains the righthand
side of the equation.
 LDB (input) INTEGER

The leading dimension of the matrix B. LDB >= max(1,N1).
 SCALE (output) DOUBLE PRECISION

On exit, SCALE contains the scale factor. SCALE is chosen
less than or equal to 1 to prevent the solution overflowing.
 X (output) DOUBLE PRECISION array, dimension (LDX,2)

On exit, X contains the N1 by N2 solution.
 LDX (input) INTEGER

The leading dimension of the matrix X. LDX >= max(1,N1).
 XNORM (output) DOUBLE PRECISION

On exit, XNORM is the infinitynorm of the solution.
 INFO (output) 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.
Pages related to dlasy2
 dlasy2 (3)
 dlasyf (l)  computes a partial factorization of a real symmetric matrix A using the BunchKaufman diagonal pivoting method
 dlas2 (l)  computes the singular values of the 2by2 matrix [ F G ] [ 0 H ]
 dlascl (l)  multiplies the M by N real matrix A by the real scalar CTO/CFROM
 dlascl2 (l)  performs a diagonal scaling on a vector
 dlasd0 (l)  a divide and conquer approach, DLASD0 computes the singular value decomposition (SVD) of a real upper bidiagonal NbyM matrix B with diagonal D and offdiagonal E, where M = N + SQRE
 dlasd1 (l)  computes the SVD of an upper bidiagonal NbyM matrix B,
 dlasd2 (l)  merges the two sets of singular values together into a single sorted set
 dlasd3 (l)  finds all the square roots of the roots of the secular equation, as defined by the values in D and Z
 dlasd4 (l)  subroutine compute the square root of the Ith updated eigenvalue of a positive symmetric rankone modification to a positive diagonal matrix whose entries are given as the squares of the corresponding entries in the array d, and that 0 <= D(i) < D(j) for i < j and that RHO > 0