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115 lines
4.0 KiB
115 lines
4.0 KiB
.\"
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.\" $Id: random_range.3,v 1.1 2000/07/27 16:59:03 alaffin Exp $
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.\"
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.\" Copyright (c) 2000 Silicon Graphics, Inc. All Rights Reserved.
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.\"
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.\" This program is free software; you can redistribute it and/or modify it
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.\" under the terms of version 2 of the GNU General Public License as
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.\" published by the Free Software Foundation.
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.\"
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.\" This program is distributed in the hope that it would be useful, but
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.\" WITHOUT ANY WARRANTY; without even the implied warranty of
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.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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.\"
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.\" Further, this software is distributed without any warranty that it is
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.\" free of the rightful claim of any third person regarding infringement
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.\" or the like. Any license provided herein, whether implied or
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.\" otherwise, applies only to this software file. Patent licenses, if
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.\" any, provided herein do not apply to combinations of this program with
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.\" other software, or any other product whatsoever.
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.\"
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.\" You should have received a copy of the GNU General Public License along
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.\" with this program; if not, write the Free Software Foundation, Inc.,
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.\" 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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.\"
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.\" Contact information: Silicon Graphics, Inc., 1600 Amphitheatre Pkwy,
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.\" Mountain View, CA 94043, or:
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.\"
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.\" http://www.sgi.com
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.\"
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.\" For further information regarding this notice, see:
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.\" http://oss.sgi.com/projects/GenInfo/NoticeExplan/
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.\"
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.TH random_range 3 07/25/2000 "Linux Test Project"
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.SH NAME
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random_range \- a set of routines for dealing with integer ranges, and random numbers in a range
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.SH SYNOPSIS
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.nf
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void random_range_seed(int seed)
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long random_range(int min, int max, int mult, char **errp)
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long random_rangel(long min, long max, long mult, char **errp)
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long long random_rangell(long long min, long long max,
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long long mult, char **errp)
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long random_bit(long mask)
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.fi
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.SH DESCRIPTION
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This is a set of routines for parsing numeric ranges, and choosing random
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numbers from a range.
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random_range() chooses a random number in the range min-max (inclusive) which
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is a multiple of mult. min and max may be any integer, but mult must be
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a positive integer greater than 0. errp is a char ** which is used to detect
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error conditions. If errp is not NULL, *errp will be set to point to an
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error message. If errp is NULL, error conditions cannot be detected by the
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caller. If mult is 1 (the most common case), there are no possible error
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conditions, and the return value is guaranteed to be valid.
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random_range_seed() sets the random number generator seed to the specified
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value.
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random_bit() will return a randomly selected single bit bitmask from the bits
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set in mask. The bit is randomly chosen using random_range().
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If mask is zero, zero is returned.
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random_range() functions uses lrand48() internally. If the range is bigger
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than will fit in a 32 bit long (2G), lrand48() with a
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a internal recursive algorithm to produce a random number.
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.SH EXAMPLES
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\fC
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.ta .25i +.25i +.25i +.25i
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.nf
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#include <stdio.h>
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main(argc, argv)
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int argc;
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char **argv;
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{
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int r;
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char *errp;
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extern void random_range_seed();
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extern long random_range();
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random_range_seed(getpid());
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r = random_range(atoi(argv[1]), atoi(argv[2]), atoi(argv[3]), &errp);
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if (errp == NULL) {
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fprintf(stderr, "random_range failed: %s\n", errp);
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exit(1);
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} else {
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printf("%d\n", r);
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}
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exit(0);
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}
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\fP
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.fi
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.SH "SEE ALSO"
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lrand48(3c)
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.SH DIAGNOSTICS
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If random_range() fails, errp will point to NULL, and the return value will be
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undefined. If mult is 1, there are no possible error conditions, so the return
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value is always valid in this case.
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.SH BUGS
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On CRAY systems, random_range(), random_rangel(), random_rangell()
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all have the 64 bit limit since int, long and long long are always 64 bits.
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On IRIX systems, random_range() can only produce a 32 number.
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random_rangel() when compiled as a 32 bit object is still limited to 32 bit
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number. random_rangell() can be used to return a value bigger than 32 bits
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even when compiled as a 32 bit object.
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