dlasy2.f(3)

NAME
dlasy2.f -

SYNOPSIS

  Functions/Subroutines
subroutine DLASY2 (LTRANL, LTRANR, ISGN, N1, N2, TL, LDTL, TR, LDTR, B, LDB, SCALE, X, LDX, XNORM, INFO)
DLASY2

Function/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

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 or
     -1.  op(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:
    November 2011

Definition at line 174 of file dlasy2.f'.

Author

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