LAPACK 3.3.1
Linear Algebra PACKage

dlat2s.f

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00001       SUBROUTINE DLAT2S( UPLO, N, A, LDA, SA, LDSA, INFO )
00002 *
00003 *  -- LAPACK PROTOTYPE auxiliary routine (version 3.3.1) --
00004 *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
00005 *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
00006 *  -- April 2011                                                      --
00007 *
00008 *     .. Scalar Arguments ..
00009       CHARACTER          UPLO
00010       INTEGER            INFO, LDA, LDSA, N
00011 *     ..
00012 *     .. Array Arguments ..
00013       REAL               SA( LDSA, * )
00014       DOUBLE PRECISION   A( LDA, * )
00015 *     ..
00016 *
00017 *  Purpose
00018 *  =======
00019 *
00020 *  DLAT2S converts a DOUBLE PRECISION triangular matrix, SA, to a SINGLE
00021 *  PRECISION triangular matrix, A.
00022 *
00023 *  RMAX is the overflow for the SINGLE PRECISION arithmetic
00024 *  DLAS2S checks that all the entries of A are between -RMAX and
00025 *  RMAX. If not the convertion is aborted and a flag is raised.
00026 *
00027 *  This is an auxiliary routine so there is no argument checking.
00028 *
00029 *  Arguments
00030 *  =========
00031 *
00032 *  UPLO    (input) CHARACTER*1
00033 *          = 'U':  A is upper triangular;
00034 *          = 'L':  A is lower triangular.
00035 *
00036 *  N       (input) INTEGER
00037 *          The number of rows and columns of the matrix A.  N >= 0.
00038 *
00039 *  A       (input) DOUBLE PRECISION array, dimension (LDA,N)
00040 *          On entry, the N-by-N triangular coefficient matrix A.
00041 *
00042 *  LDA     (input) INTEGER
00043 *          The leading dimension of the array A.  LDA >= max(1,N).
00044 *
00045 *  SA      (output) REAL array, dimension (LDSA,N)
00046 *          Only the UPLO part of SA is referenced.  On exit, if INFO=0,
00047 *          the N-by-N coefficient matrix SA; if INFO>0, the content of
00048 *          the UPLO part of SA is unspecified.
00049 *
00050 *  LDSA    (input) INTEGER
00051 *          The leading dimension of the array SA.  LDSA >= max(1,M).
00052 *
00053 *  INFO    (output) INTEGER
00054 *          = 0:  successful exit.
00055 *          = 1:  an entry of the matrix A is greater than the SINGLE
00056 *                PRECISION overflow threshold, in this case, the content
00057 *                of the UPLO part of SA in exit is unspecified.
00058 *
00059 *  =====================================================================
00060 *
00061 *     .. Local Scalars ..
00062       INTEGER            I, J
00063       DOUBLE PRECISION   RMAX
00064       LOGICAL            UPPER
00065 *     ..
00066 *     .. External Functions ..
00067       REAL               SLAMCH
00068       LOGICAL            LSAME
00069       EXTERNAL           SLAMCH, LSAME
00070 *     ..
00071 *     .. Executable Statements ..
00072 *
00073       RMAX = SLAMCH( 'O' )
00074       UPPER = LSAME( UPLO, 'U' )
00075       IF( UPPER ) THEN
00076          DO 20 J = 1, N
00077             DO 10 I = 1, J
00078                IF( ( A( I, J ).LT.-RMAX ) .OR. ( A( I, J ).GT.RMAX ) )
00079      $             THEN
00080                   INFO = 1
00081                   GO TO 50
00082                END IF
00083                SA( I, J ) = A( I, J )
00084    10       CONTINUE
00085    20    CONTINUE
00086       ELSE
00087          DO 40 J = 1, N
00088             DO 30 I = J, N
00089                IF( ( A( I, J ).LT.-RMAX ) .OR. ( A( I, J ).GT.RMAX ) )
00090      $             THEN
00091                   INFO = 1
00092                   GO TO 50
00093                END IF
00094                SA( I, J ) = A( I, J )
00095    30       CONTINUE
00096    40    CONTINUE
00097       END IF
00098    50 CONTINUE
00099 *
00100       RETURN
00101 *
00102 *     End of DLAT2S
00103 *
00104       END
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