set.seed and /dev/random

On 2 May 2009 at 18:53, Saptarshi Guha wrote:
| Hello,
| In ?set.seed I notice that a seed is created from the system time.
| Thus if two machines were (hypothetically) running for the same time
| and R was started simultaneously on both, the would have the same
| seeds (correct?).
|
| I assume reading from /dev/random would be different for both of these
| machines, so my question is why not use an integer read from
| /dev/random to create the seed?

Some folks do. But do read the fine print about entropy etc.

An alternnative is provided by the random package on CRAN (slightly
re-indented below).

Dirk


R> library(help=random)

? ? ? ? ? ? ? ?Information on package 'random'

Description:

Package: ? ? ? random
Version: ? ? ? 0.2.0
Date: ? ? ? ? ?$Date: 2009-01-03 11:45:17 -0600 (Sat, 03 Jan 2009) $
Author: ? ? ? ?Dirk Eddelbuettel <edd at debian.org>
Maintainer: ? ?Dirk Eddelbuettel <edd at debian.org>
Title: ? ? ? ? True random numbers using random.org
Description: ? This package provides an interface to the true random number
? ? ? ? ? ? ? service provided by the random.org website created by Mads
? ? ? ? ? ? ? Haahr. ?The random.org web service samples atmospheric noise
? ? ? ? ? ? ? via radio tuned to an unused broadcasting frequency together
? ? ? ? ? ? ? with a skew correction algorithm due to John von Neumann.
? ? ? ? ? ? ? More background is available in the included vignette based on
? ? ? ? ? ? ? an essay by Mads Haahr. In its current form, the package
? ? ? ? ? ? ? offers functions to retrieve random integers, randomized
? ? ? ? ? ? ? sequences and random strings.
Depends: ? ? ? R (>= 2.8.0)
License: ? ? ? GPL Version 2
URL: ? ? ? ? ? http://www.random.org
Built: ? ? ? ? R 2.8.1; ; 2009-01-03 11:46:25; unix

Index:

random ? ? ? ? ? ? ? ? ?True random numbers from random.org

Further information is available in the following vignettes in directory
'/usr/local/lib/R/site-library/random/doc':

random-essay: random.org: Introduction to Randomness and Random Numbers (source, pdf)
random-intro: random: An R package for true random numbers (source, pdf)

R>


| Would it be a portability issue?
| I must admit I have very little idea about RNGs, so my question is
| possibly very naive.
|
| Thank you
| Saptarshi
|
| ______________________________________________
| R-devel at r-project.org mailing list
| https://stat.ethz.ch/mailman/listinfo/r-devel

--
Three out of two people have difficulties with fractions.

Hello,
In ?set.seed I notice that a seed is created from the system time.
Thus if two machines were (hypothetically) running for the same time
and R was started simultaneously on both, the would have the same
seeds (correct?).

I assume reading from /dev/random would be different for both of these
machines, so my question is why not use an integer read from
/dev/random to create the seed?

Would it be a portability issue?