Genrate all combinations of a vector

I have a vector of size n, whose each element can be an integer in the range from 0 to k. I need to generate all possible variants of such vector, i.e. k^n vectors totally.

The solutions I have found haven't met my need:
- allcomb.m doesn't work with n>=100. I got the following error 
    Maximum variable size allowed by the program is exceeded.

      Error in ndgrid (line 66)
           x = reshape(x(:,ones(1,prod(s))),[length(x) s]); % Expand x

   - perms only generates possible permutations of the n elements of v.

I wonder if there is any function in matlab that does what I need? 

Thanks,

[Titus Edelhofer]

What values of k and n are you targeting?

[Walter Roberson]

Have you calculated how much storage space storing those combinations will occupy?

Have you estimated how long it will take to generate all of the combinations?

[Khanh]

@Titus: I had problem when trying n=100, and k =3, which means 4^100=1.6e^60.

@Walter: I don't know much about the data type in matlab. I don't know how many bytes are used to store a vector of size n.

But I think you guys made a good point. I think even with n=100, k=3, it's too big for my desktop.

Thanks.

[Walter Roberson]

If you used one byte per element of the vector (e.g., uint8 data type), then you would have n bytes per entry, and (k+1)^n entries, for a total of approximately n*(k+1)^n bytes.

For n=100 and k=3, that would be 100*4^100 which would be about 1.6E62 bytes.

1 gigabyte is approximately 10^9 bytes, so you are asking for approximately 1.6E53 gigabytes.

So how much can you realistically store in (say) 4 gigabytes (the maximum address space for a 32 bit process)? n*4^n = 2^32 solves down to n = (1/2)*LambertW(8589934592*ln(2))/ln(2) which is a little over 14.

Thus, you realistically cannot produce all the combinations for vectors of length greater than 14.

[Khanh]

You're absolutely right, Walter. Thanks a lot for your effort. I should've thought about the memory issue before :( It was such a dump question.