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#include <sla_config.h>
REAL FUNCTION sla_RANDOM (SEED)
*+
* - - - - - - -
* R A N D O M
* - - - - - - -
*
* Generate pseudo-random real number in the range 0 <= X < 1.
* (single precision)
*
*
* Given:
* SEED real an arbitrary real number
*
* Notes:
*
* 1) The result is a pseudo-random REAL number in the range
* 0 <= sla_RANDOM < 1.
*
* 2) SEED is used first time through only.
*
* Called: RAN or RAND (a REAL function returning a random variate --
* the precise function which is called depends on which functions
* are available when the library is built). If neither of these
* is available, we use the local substitute RANDOM defined
* in rtl_random.c
*
* P.T.Wallace Starlink 14 October 1991
*
* License:
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program (see SLA_CONDITIONS); if not, write to the
* Free Software Foundation, Inc., 59 Temple Place, Suite 330,
* Boston, MA 02111-1307 USA
*-
IMPLICIT NONE
REAL SEED
#if HAVE_RAND
REAL RAND
#elif HAVE_RANDOM
REAL RANDOM
#else
error "Can't find random-number function"
#endif
REAL AS
INTEGER ISEED
LOGICAL FIRST
SAVE FIRST
DATA FIRST /.TRUE./
* If first time, turn SEED into a large, odd integer
IF (FIRST) THEN
AS=ABS(SEED)+1.0
ISEED=NINT(AS/10.0**(NINT(ALOG10(AS))-6))
IF (MOD(ISEED,2).EQ.0) ISEED=ISEED+1
FIRST=.FALSE.
#if HAVE_RAND
AS = RAND(ISEED)
#endif
ELSE
ISEED=0
END IF
* Next pseudo-random number
#if HAVE_RAND
sla_RANDOM=RAND(0)
#elif HAVE_RANDOM
sla_RANDOM=RANDOM(ISEED)
#endif
END