1DLASY2(1)           LAPACK auxiliary routine (version 3.2)           DLASY2(1)
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NAME

6       DLASY2  -  solves  for  the  N1  by  N2  matrix  X, 1 <= N1,N2 <= 2, in
7       op(TL)*X + ISGN*X*op(TR) = SCALE*B,
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SYNOPSIS

10       SUBROUTINE DLASY2( LTRANL, LTRANR, ISGN, N1, N2, TL, LDTL, TR, LDTR, B,
11                          LDB, SCALE, X, LDX, XNORM, INFO )
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13           LOGICAL        LTRANL, LTRANR
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15           INTEGER        INFO, ISGN, LDB, LDTL, LDTR, LDX, N1, N2
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17           DOUBLE         PRECISION SCALE, XNORM
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19           DOUBLE         PRECISION B( LDB, * ), TL( LDTL, * ), TR( LDTR, * ),
20                          X( LDX, * )
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PURPOSE

23       DLASY2 solves for the N1 by N2 matrix X, 1 <= N1,N2 <= 2, in  where  TL
24       is  N1 by N1, TR is N2 by N2, B is N1 by N2, and ISGN = 1 or -1.  op(T)
25       = T or T', where T' denotes the transpose of T.
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ARGUMENTS

28       LTRANL  (input) LOGICAL
29               On entry, LTRANL specifies the op(TL): = .FALSE., op(TL) =  TL,
30               = .TRUE., op(TL) = TL'.
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32       LTRANR  (input) LOGICAL
33               On  entry, LTRANR specifies the op(TR): = .FALSE., op(TR) = TR,
34               = .TRUE., op(TR) = TR'.
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36       ISGN    (input) INTEGER
37               On entry, ISGN specifies the sign of the equation as  described
38               before. ISGN may only be 1 or -1.
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40       N1      (input) INTEGER
41               On  entry, N1 specifies the order of matrix TL.  N1 may only be
42               0, 1 or 2.
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44       N2      (input) INTEGER
45               On entry, N2 specifies the order of matrix TR.  N2 may only  be
46               0, 1 or 2.
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48       TL      (input) DOUBLE PRECISION array, dimension (LDTL,2)
49               On entry, TL contains an N1 by N1 matrix.
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51       LDTL    (input) INTEGER
52               The leading dimension of the matrix TL. LDTL >= max(1,N1).
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54       TR      (input) DOUBLE PRECISION array, dimension (LDTR,2)
55               On entry, TR contains an N2 by N2 matrix.
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57       LDTR    (input) INTEGER
58               The leading dimension of the matrix TR. LDTR >= max(1,N2).
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60       B       (input) DOUBLE PRECISION array, dimension (LDB,2)
61               On entry, the N1 by N2 matrix B contains the right-hand side of
62               the equation.
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64       LDB     (input) INTEGER
65               The leading dimension of the matrix B. LDB >= max(1,N1).
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67       SCALE   (output) DOUBLE PRECISION
68               On exit, SCALE contains the scale factor. SCALE is chosen  less
69               than or equal to 1 to prevent the solution overflowing.
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71       X       (output) DOUBLE PRECISION array, dimension (LDX,2)
72               On exit, X contains the N1 by N2 solution.
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74       LDX     (input) INTEGER
75               The leading dimension of the matrix X. LDX >= max(1,N1).
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77       XNORM   (output) DOUBLE PRECISION
78               On exit, XNORM is the infinity-norm of the solution.
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80       INFO    (output) INTEGER
81               On exit, INFO is set to 0: successful exit.
82               1:  TL  and  TR have too close eigenvalues, so TL or TR is per‐
83               turbed to get a nonsingular equation.  NOTE: In  the  interests
84               of speed, this routine does not check the inputs for errors.
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88 LAPACK auxiliary routine (versionNo3v.e2m)ber 2008                       DLASY2(1)