Generating random number within a specific range (0.5-1.5) Post: 302303915

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Top Forums Shell Programming and Scripting Generating random number within a specific range (0.5-1.5) Post 302303915 by drl on Friday 3rd of April 2009 11:42:25 PM

04-04-2009

Registered User

Hi.

Here is one method:

Code:

#!/usr/bin/env bash

# @(#) s1       Demonstrate obtaining vector of truly random values.

echo
set +o nounset
LC_ALL=C ; LANG=C ; export LC_ALL LANG
echo "Environment: LC_ALL = $LC_ALL, LANG = $LANG"
echo "(Versions displayed with local utility \"version\")"
version >/dev/null 2>&1 && version "=o" $(_eat $0 $1) awk qrandom
set -o nounset

echo
echo " Results, 0-1:"
qrandom 10

echo
echo " Results, 0.5 - 1.5:"
qrandom 10 |
awk '
{ t = $0 + 0.5 ; printf("%.2f\n",t) }
'

exit 0

Producing a sequence (0,1) and (.5,1.5):

Code:

% ./s1

Environment: LC_ALL = C, LANG = C
(Versions displayed with local utility "version")
OS, ker|rel, machine: Linux, 2.6.11-x1, i686
Distribution        : Xandros Desktop 3.0.3 Business
GNU bash 2.05b.0
GNU Awk 3.1.4
qrandom (local) 1.0

 Results, 0-1:
0.4673012
0.7736701
0.9535608
0.1947628
0.8967344
0.4138898
0.9485450
0.6075562
0.9707173
0.2477338

 Results, 0.5 - 1.5:
1.27
0.57
1.00
1.01
1.26
1.47
0.63
0.84
0.92
0.91

The random number vector is obtained from an Internet service:

Quote:

We use 'Quantum Random Bit Generator' (QRBG121), which is a fast non-deterministic random bit (number) generator whose randomness relies on intrinsic randomness of the quantum physical process of photonic emission in semiconductors and subsequent detection by photoelectric effect.

More at: Quantum Random Bit Generator Service

Best wishes ... cheers, drl

drl

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LEARN ABOUT OPENSOLARIS

srand

rand(3UCB)					     SunOS/BSD Compatibility Library Functions						rand(3UCB)

NAME

       rand, srand - simple random number generator

SYNOPSIS

       /usr/ucb/cc [ flag ... ] file ...

       int rand();

       int srand(seed)
       unsigned seed;

DESCRIPTION

       rand()  uses a multiplicative congruential random number generator with period 2^32 to return successive pseudo-random numbers in the range
       from 0 to 2^31 -1.

       srand() can be called at any time to reset the random-number generator to a random starting point. The generator is initially seeded with a
       value of 1.

SEE ALSO

       cc(1B), drand48(3C), rand(3C), random(3C)

NOTES

       Use of these interfaces should be restricted to only applications written on BSD platforms.  Use of these interfaces with any of the system
       libraries or in multi-thread applications is unsupported.

       The spectral properties of rand() leave a great deal to be desired. drand48(3C) and random(3C) provide much better, though more	elaborate,
       random-number generators.

       The low bits of the numbers generated are not very random; use the middle bits. In particular the lowest bit alternates between 0 and 1.

SunOS 5.11							    30 Oct 2007 							rand(3UCB)

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