Can any tell me why rand() is such a bad pseudo-random number generator.
In all the articles I have read they say that you can predict the outcome
of rand() but when I used its output with NIST's random number testsuite
it passed all of the tests thrown at it for randomness. Can anyone
suggest a test I could use that it would fail? A pointer to a suitable
article would be appreciated.
Thanks for your help in advance,
Tom
--
Using M2, Opera's revolutionary e-mail client: http://www.opera.com/m2/
Jul 22 '05
11  4225 
AngleWyrm writes: One of the problems with the standard implementation of rand() is that on
most systems it uses a fast formula called Linear Congruential.
But there IS NO STANDARD implementation of rand(). It is the name of a
FUNCTION, not an ALGORITHM!!!
"osmium" <r1********@com cast.net> wrote in message
news:2o******** ****@uni-berlin.de... AngleWyrm writes:
One of the problems with the standard implementation of rand() is that
on most systems it uses a fast formula called Linear Congruential.
But there IS NO STANDARD implementation of rand(). It is the name of a
FUNCTION, not an ALGORITHM!!!
You don't program much, do you? http://home.comcast.net/~anglewyrm/hat.html This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
by: Chris Gordon-Smith |
last post by:
I have a simulation program that calls the rand() function at various points
while it executes.
For the user interface that displays statistics etc. while the program runs,
I use the Lazarus GUI library, which is based on GTK. Depending on which
libraries I link in, I can have either a GTK1 or GTK2 user interface.
I'm finding that the simulation behaves differently depending on whether I
link with GTK1 or GTK2.
|
by: Ben Justice |
last post by:
For a program in c, I need some random numbers for a system were people are
placing bets. This is not a commerical project btw. Generally, I tend to
rely on things from the standard library, because they're written by people
with skills far above mine. Hence, I've always used rand() and FALSELY
assumed it could produce unpredictable random numbers and could be used in
many situations even if security was an issue.
Firstly, lets assume...
|
by: Profetas |
last post by:
Hi,
I want to generate a random 8 bit number using rand(0
is that possible? to expecifu the base and the lenght?
thanks
|
by: Jack |
last post by:
When I use rand(), is the RAND_MAX value how long I am guaranteed that
the same value will not appear twice?
And is this a floating window?
For example, if RAND_MAX is 32767, and I make 500,000 consecutive rand
calls then is the rand() algorithm going to guarantee me that no
floating window of calls over that 500,000 rand calls will have the
same value twice? The only way that would work is if the series was
identical everytime.
|
by: Siam |
last post by:
Hi all,
I'm writing a shell language in c++ that supports the generation of
random numbers, and by its nature, each command must be executed in a
new thread. The call to the random function from my language simply
propogates up to the rand( ) function from c++. For some reason, C++
will give each thread independent use of their own rand( ) function, so
that a rand( ) call from one thread won't affect another thread's call
to rand( )....
| | |
by: Spiros Bousbouras |
last post by:
The standard says that rand() should return a pseudo-random
number but what does pseudorandom mean ? If an implementation
of rand() always returned the same number would it be conforming ?
What if it always alternated between 2 values ?
On the practical side do you have any thoughts on what one
could realistically expect from the behaviour of rand() ? Could
for example one expect that eventually any value in the range
will be returned ?
|
by: ds |
last post by:
Hi all,
rand() is not thread safe, a fact that may not be so bad after all..
However, I face the following problem: a piece of code uses rand() to
get a random sequence, but always seeds with the same seed for
reproducibility of the results. Now I am porting this (old C89) code
and have setup a nice app with threads that drives on one thread the
old code and on another the new code, so that I can compare the
results and see that nothing...
|
by: Rafael Cunha de Almeida |
last post by:
Hi,
I've found several sites on google telling me that I shouldn't use
rand() % range+1
and I should, instead, use something like:
lowest+int(range*rand()/(RAND_MAX + 1.0))
|
by: Rich Fife |
last post by:
Quick rand() question:
I know you're not supposed to use "rand() % 1024" for instance,
because it focuses on the lower bits. However, it seems to me that
given that the argument is not a power of two (or near a power of
two), that this is not an issue. The upper bits will participate
equally in the result with the lower. Am I missing something?
Thanks!
|
by: marktang |
last post by:
ONU (Optical Network Unit) is one of the key components for providing high-speed Internet services. Its primary function is to act as an endpoint device located at the user's premises. However, people are often confused as to whether an ONU can Work As a Router. In this blog post, we’ll explore What is ONU, What Is Router, ONU & Router’s main usage, and What is the difference between ONU and Router. Let’s take a closer look !
Part I. Meaning of...
|
by: Hystou |
last post by:
Most computers default to English, but sometimes we require a different language, especially when relocating. Forgot to request a specific language before your computer shipped? No problem! You can effortlessly switch the default language on Windows 10 without reinstalling. I'll walk you through it.
First, let's disable language synchronization. With a Microsoft account, language settings sync across devices. To prevent any complications,...
| | |
by: tracyyun |
last post by:
Dear forum friends,
With the development of smart home technology, a variety of wireless communication protocols have appeared on the market, such as Zigbee, Z-Wave, Wi-Fi, Bluetooth, etc. Each protocol has its own unique characteristics and advantages, but as a user who is planning to build a smart home system, I am a bit confused by the choice of these technologies. I'm particularly interested in Zigbee because I've heard it does some...
|
by: agi2029 |
last post by:
Let's talk about the concept of autonomous AI software engineers and no-code agents. These AIs are designed to manage the entire lifecycle of a software development project—planning, coding, testing, and deployment—without human intervention. Imagine an AI that can take a project description, break it down, write the code, debug it, and then launch it, all on its own....
Now, this would greatly impact the work of software developers. The idea...
|
by: isladogs |
last post by:
The next Access Europe User Group meeting will be on Wednesday 1 May 2024 starting at 18:00 UK time (6PM UTC+1) and finishing by 19:30 (7.30PM).
In this session, we are pleased to welcome a new presenter, Adolph Dupré who will be discussing some powerful techniques for using class modules.
He will explain when you may want to use classes instead of User Defined Types (UDT). For example, to manage the data in unbound forms.
Adolph will...
|
by: adsilva |
last post by:
A Windows Forms form does not have the event Unload, like VB6. What one acts like?
|
by: 6302768590 |
last post by:
Hai team
i want code for transfer the data from one system to another through IP address by using C# our system has to for every 5mins then we have to update the data what the data is updated we have to send another system
|
by: muto222 |
last post by:
How can i add a mobile payment intergratation into php mysql website.
| | |
by: bsmnconsultancy |
last post by:
In today's digital era, a well-designed website is crucial for businesses looking to succeed. Whether you're a small business owner or a large corporation in Toronto, having a strong online presence can significantly impact your brand's success. BSMN Consultancy, a leader in Website Development in Toronto offers valuable insights into creating effective websites that not only look great but also perform exceptionally well. In this comprehensive...
| |
