da/da0/drshft_8f_source.html

00001       SUBROUTINE DRSHFT( M, N, OFFSET, A, LDA )
00002 *
00003 *  -- PBLAS auxiliary routine (version 2.0) --
00004 *     University of Tennessee, Knoxville, Oak Ridge National Laboratory,
00005 *     and University of California, Berkeley.
00006 *     April 1, 1998
00007 *
00008 *     .. Scalar Arguments ..
00009       INTEGER            LDA, M, N, OFFSET
00010 *     ..
00011 *     .. Array Arguments ..
00012       DOUBLE PRECISION   A( LDA, * )
00013 *     ..
00014 *
00015 *  Purpose
00016 *  =======
00017 *
00018 *  DRSHFT shifts rows of an m by n array A by OFFSET.
00019 *
00020 *  Arguments
00021 *  =========
00022 *
00023 *  M       (local input) INTEGER
00024 *          On entry, M  specifies the number of rows of A to be shifted.
00025 *          M must be at least zero.
00026 *
00027 *  N       (local input) INTEGER
00028 *          On entry,  N  specifies the number of columns of A. N must be
00029 *          at least zero.
00030 *
00031 *  OFFSET  (local input) INTEGER
00032 *          On entry, OFFSET  specifies  the  offset by which the rows of
00033 *          A should be shifted. OFFSET  can be positive or negative (see
00034 *          below for further details). When OFFSET is positive, the rows
00035 *          are shifted to the  bottom. When OFFSET is negative, the rows
00036 *          of A are shifted to the top.
00037 *
00038 *  A       (local input/local output) DOUBLE PRECISION array
00039 *          On entry,  A  is an array of dimension ( LDA, N ). On exit, A
00040 *          contains the shifted array.
00041 *
00042 *  LDA     (local input) INTEGER
00043 *          On entry, LDA specifies the leading dimension of the array A.
00044 *          LDA must be at least max( 1, M+ABS(OFFSET) ).
00045 *
00046 *  Further Details
00047 *  ===============
00048 *
00049 *            N                 N                   N                 N
00050 *           ---               ---                 ---               ---
00051 *          | 1 |             | 1 |               | 1 |             | 7 |
00052 *          | 2 |    M = 3    | 2 |               | 2 |    M = 3    | 8 |
00053 *          | 3 |             | 3 |               | 3 |             | 9 |
00054 *          | 4 |             | 4 |               | 4 |             | 4 |
00055 *          | 5 |   becomes   | 5 |               | 5 |   becomes   | 5 |
00056 *          | 6 |             | 6 |               | 6 |             | 6 |
00057 *          | 7 |             | 1 |               | 7 |             | 7 |
00058 *          | 8 | OFFSET =  6 | 2 |               | 8 | OFFSET = -6 | 8 |
00059 *          | 9 |             | 3 |               | 9 |             | 9 |
00060 *           ---               ---                 ---               ---
00061 *                OFFSET >= 0                           OFFSET <= 0
00062 *
00063 *  -- Written on April 1, 1998 by
00064 *     Antoine Petitet, University  of  Tennessee, Knoxville 37996, USA.
00065 *
00066 *  =====================================================================
00067 *
00068 *     .. Local Scalars ..
00069       INTEGER            I, J
00070 *     ..
00071 *     .. Executable Statements ..
00072 *
00073       IF( ( OFFSET.EQ.0 ).OR.( M.LE.0 ).OR.( N.LE.0 ) )
00074      $   RETURN
00075 *
00076       IF( OFFSET.GT.0 ) THEN
00077          DO 20 J = 1, N
00078             DO 10 I = M, 1, -1
00079                A( I+OFFSET, J ) = A( I, J )
00080    10       CONTINUE
00081    20    CONTINUE
00082       ELSE
00083          DO 40 J = 1, N
00084             DO 30 I = 1, M
00085                A( I, J ) = A( I-OFFSET, J )
00086    30       CONTINUE
00087    40    CONTINUE
00088       END IF
00089 *
00090       RETURN
00091 *
00092 *     End of DRSHFT
00093 *
00094       END