>> RandStream.getGlobalStream
ans =
mt19937ar random stream (current global stream)
Seed: 0
NormalTransform: Ziggurat

Note that getGlobalStream is a new name (in R2011a of the getDefaultStream method from earlier releases. If you want to assign the value to a variable, it’s the .Seed property of that stream.

In R2011a and later, there’s a new simpler interface to controlling random numbers, for non-parallel cases:

>> rng
ans =
Type: ‘twister’
Seed: 0
State: [625x1 uint32]

It’s described here : http://www.mathworks.com/help/techdoc/math/bs1qb_i.html

stream = RandStream.getDefaultStream

and things like

rand(’state’,11)

In this particular case, as I read your code, you’re getting and using the default random number stream in your main code, but your function changes the default stream to something else, and that has global effects. So when you get back to your main code, the default stream is no longer what it was when you saved its state, and while

stream.State = savedState;

does indeed reset the stream’s state, the subsequent call to rand DOESN’T USE that stream because the calls to rand inside your function call have changed the default.

I don’t know what you intend

s= get(stream)

to do, but

RandStream.setDefaultStream(stream)

is probably what you meant to do, and would solve the problem.

Some notes:

1) The calls like rand(’state’,11) use an old syntax, one that has not been recommended for several years, and one that you probably don’t want to mix with calls to RandStream methods, not because it won’t work, but because you will get confused.

2) The term “default stream” refers to “the random number stream that rand/randi/randn use by default”, but since RandStream was introduced in 2008, we found that the term is somewhat confusing. So in R2011a, the doc describes this as “the global random number stream”, and the methods RandStream.get/setGlobalStream are now preferred.

3) I recommend that in your function, you create a local stream, and call rand using that to generate numbers. This will not affect the global stream at all. This strategy described in these blog posts.

4) If you are using R2011a, you may find that the new RNG function, described in another blog post here:

http://blogs.mathworks.com/loren/2011/07/07/simpler-control-of-random-number-generation-in-matlab/

is simpler for your needs. In fact, the second help example

http://www.mathworks.com/help/techdoc/ref/rng.html

does exactly what you want.

clc; clear; close all;
stream = RandStream.getDefaultStream
savedState = stream.State;
for 1=1:100
u1 = rand(1,5)
end

%function call(using fixed random state)
rand(‘state’,11)
x = rand(1,5)
rand(‘state’,125)
y=rand(1,5)

%back to the main program
s= get(stream)
stream.State = savedState;
for j=1:100
u2 = rand(1,5)
end

but the problem is when I come back to the main program I am getting the same random numbers as I get previously.

I would be glad to get your respond.

For the initial distributions, initialize the random stream:
savedSeed = sum(100*clock);
RandStream.setDefaultStream(RandStream(‘mt19937ar’,'seed’,savedSeed));
defaultStream = RandStream.getDefaultStream;
savedState = defaultStream.State;
save(‘RandInit’, ‘savedSeed’, ‘savedState’);

To re-generate the same distributions again later:
load RandInit.mat
RandStream.setDefaultStream(RandStream(‘mt19937ar’,'seed’,savedSeed));
defaultStream = RandStream.getDefaultStream;
defaultStream.State = savedState;

I don’t think I could have worked this out without the benefit of the descriptions and examples shown in the two parts of “New Ways With Random Numbers”.
Thanks,
Joe

You created defaultStream by calling getDefaultStream. But even though you named it “defaultStream” doesn’t mean that someone can’t change the default stream out from under you. Your defaultStream will remain a valid stream, but not necessarily the default stream. I suspect that you ran code (a doc example?) that had something like “rand(‘state’,0)” in it. That will change the default stream so that your defaultStream will no longer be the thing that the rand function uses.

Yes, the help says that the seed must be an integer. But over the years MATLAB users have grown accustomed to typing sum(100*clock), and there didn’t seem to be any point in requiring anyone to now start typing round(sum(100*clock)). If you do what the help says, you’ll be fine. But if you deviate slightly because of historical reasons, you’ll get something sensible (and consistent with behavior in the older syntax).