Seeding Random Numbers in Multiple Threads?

HumanJHawkins

I wrote this question a little differently in the MFC group since it is
a bit of a different environment than pure C++, but I hope you will
forgive the similarities if anyone is reading both groups.

Basically, I need to seed the random number generator in 4 seperate
threads at once. So, I can't use the current time as the random seed,
because then all four threads end up with the same series of (therefore
non-random) numbers.

Is there a best practice for seeding multiple random number generators
at once?

Thanks in advance!

Nov 30 '06 #1

Subscribe Post Reply

3595

Steve Pope

HumanJHawkins <JH******@Locutius.Comwrote:

>I wrote this question a little differently in the MFC group since it is
a bit of a different environment than pure C++, but I hope you will
forgive the similarities if anyone is reading both groups.

Basically, I need to seed the random number generator in 4 seperate
threads at once. So, I can't use the current time as the random seed,
because then all four threads end up with the same series of (therefore
non-random) numbers.

Is there a best practice for seeding multiple random number generators
at once?

Obtain "seed" from the current time, then use

seed
seed + 1000
seed + 2000
seed + 3000

Steve

Nov 30 '06 #2

peter koch

HumanJHawkins skrev:

I wrote this question a little differently in the MFC group since it is
a bit of a different environment than pure C++, but I hope you will
forgive the similarities if anyone is reading both groups.

Basically, I need to seed the random number generator in 4 seperate
threads at once. So, I can't use the current time as the random seed,
because then all four threads end up with the same series of (therefore
non-random) numbers.

If you are talking about the standard random generator and srand, you
better check the implementation. Most probably it is not thread-safe.
In any case, by protecting rand() with a mutex (of some type - a
windows critical_section looks best), there is no reason to seed more
than once.

>
Is there a best practice for seeding multiple random number generators
at once?

If you use e.g. boost and let each thread have its own generator you
could e.g. use time and add the threadid to that value.

/Peter

Nov 30 '06 #3

Similar topics

random number code

by: Jason | last post by:

Hi, I need a way to use random numbers in c++. In my c++ project, when using the mingw compiler I used a mersenne twister that is publicly available and this did its job well. Now I have...

C / C++

seeding function

by: AngleWyrm | last post by:

Ok, I know that srand( time(NULL) ) isn't such a good idea, but I do it anyway. Why? The clock is an easy source of randomness. And I've got this sneaky suspicion that I'm not the first guy to...

C / C++

Random number generator and seeding

by: Joe | last post by:

Hi, I have been working on some code that requires a high use of random numbers within. Mostly I either have to either: 1) flip a coin i.e. 0 or 1, or 2) generate a double between 0 and 1. I...

C / C++

Random Number Not Seeding

by: Jack | last post by:

I have two files: sort_comparison.c++ my_sort.h sort_comparison.c++ calls this code in my_sort.h: void my_sort::fillArray(int arr,int n) { // const int random_number_range=1000000;

C / C++

Different seeding of srand() during a SINGLE program run

by: bobrics | last post by:

Hi, I am using srand() and would like to create different random numbers during a SINGLE execution of my program because I want to compare random cases. For now I have a switch statement within a...

C / C++

Threading / random number problem

by: Mark Rae | last post by:

Hi, My R&D department has asked me to look at threading in a Web Service written in C#, so I came up with the following code: using System; using System.ComponentModel; using...

C# / C Sharp

104

Way for computing random primes in standard C.

by: fieldfallow | last post by:

Hello all, Is there a function in the standard C library which returns a prime number which is also pseudo-random? Assuming there isn't, as it appears from the docs that I have, is there a...

C / C++

Random Seeding

by: porterboy76 | last post by:

If you only use a 32 bit seed for a random number generator, does that mean you can only ever produce a maximum of 2^32 (approx 4 billion) different sequences? What about the Mersenne Twister,...

C / C++

How can get random number in your range

by: bipi | last post by:

Dear all, I found function rand(), it can create random number but this function can not define the range of number which I want to get it, such as, I want to get random number in the range from...

C / C++

How to turn on java script in a villaon keypad mobile phone

by: Charles Arthur | last post by:

How do i turn on java script on a villaon, callus and itel keypad mobile phone

Java

Merging data from multiple Excel files

by: ryjfgjl | last post by:

In our work, we often receive Excel tables with data in the same format. If we want to analyze these data, it can be difficult to analyze them because the data is spread across multiple Excel files...

Data Management

Migrating Website to Cloud - Emmanuel Katto

by: emmanuelkatto | last post by:

Hi All, I am Emmanuel katto from Uganda. I want to ask what challenges you've faced while migrating a website to cloud. Please let me know. Thanks! Emmanuel

General

Navigating the Data Structures and Algorithms (DSA)

by: BarryA | last post by:

What are the essential steps and strategies outlined in the Data Structures and Algorithms (DSA) roadmap for aspiring data scientists? How can individuals effectively utilize this roadmap to progress...

Algorithms / Advanced Math

Looking to do Android software development, any suggestions? Is flutter better?

by: nemocccc | last post by:

hello, everyone, I want to develop a software for my android phone for daily needs, any suggestions?

General

How to build RAID in BIOS?

by: Hystou | last post by:

There are some requirements for setting up RAID: 1. The motherboard and BIOS support RAID configuration. 2. The motherboard has 2 or more available SATA protocol SSD/HDD slots (including MSATA, M.2...

Computer Hardware

What is ONU?

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,...

General

Problem With Comparison Operator <=> in G++

by: Oralloy | last post by:

Hello folks, I am unable to find appropriate documentation on the type promotion of bit-fields when using the generalised comparison operator "<=>". The problem is that using the GNU compilers,...

C / C++

The easy way to turn off automatic updates for Windows 10/11

by: Hystou | last post by:

Overview: Windows 11 and 10 have less user interface control over operating system update behaviour than previous versions of Windows. In Windows 11 and 10, there is no way to turn off the Windows...

Windows Server