Loop, function or memory problem: Loop variable in a function is limited automatically.

Hi to all,

I am processing 3D images. In one of the functions i wrote, "for" loop variable is limited to 262144 while it should not be. My loop is just like :

For i = 1 : 26214400 %( 1 : 512*512*100 ) .... end

In case it is a memory problem, i deleted some data to get more space on the memory my script uses but it did not work. The limit value does not change. I tried it on both uint8 and double data.

By the way i use Windows 7, i have 4 GB Memory. I strongly need help about this.

Thanks to all.

Ibrahim

[Robert Cumming]

what is the error message you get?

[David Young]

Could you cut and paste the actual code you use? Clearly, the example in your question is not the code, because it has "For" instead of "for".

[Gautam Vallabha]

check the size of your image (is it really 512x512x100 or is it just 512x512)?

[Ibrahim harmankaya]

Thanks Robert, David and Gautam.

@Robert Cumming :

There is no error message. It just stops and quit when i = 262144.

@David Young : Well, i did not write "For" on .m file. It is "for".

@Gautam Vallabha : In case of any mistake like that, i wrote

" for i = 1 : 26214400 " not for i = 1 : 512*512*100. And even i tried other numbers like "for i = 1 : 2000555, which is greater than 262144.

[Matt Fig]

Hmm, something weird is going on. Can you verify that this works at the command line:

for ii = 1:512*512*100,jj = ii/2;end,jj*2==512*512*100

[Ibrahim harmankaya]

@Matt : I have verified that.

[Matt Fig]

So it works at the command line, it should work in the function. There is more to the story that we cannot see because we don't have the code....

Answer 1

[Ibrahim harmankaya]

First of all, thank to you all. Well, i figured it out. I was usually setting end value of i as some value different than 26214400. So when Matt said about 512*512 which is 262144 i checked again some sub-functions called in my function. And i realized that my array limited by 512*512 by one of the sub-functions.

But the weird thing is that i would expect to get error when i try to reach (262144 + 1)th element.

Actually, i use the array to hold some indices and i check if there is any new indices added or not by using the next element of the array at the end of "for" loop :

%array was set by sub-functions as % array = zeros(262144) %and if there is no change in "i"th loop, array(i+1) is zero.

ind = 1; for i = 1 : n

   if expression_a 
     array(ind) = exp1;
     ind = ind + 1; 
   end
   if expression_b
     array(ind) = exp2;
     ind = ind + 1;
   end

   if (array(i+1) = 0), break, end

end

Wouldn't that be the error like "Index exceeds matrix dimensions" ? Or do i miss something?

Thanks again. Is there anyone currently working on medical image processing?

[Ibrahim harmankaya]

And i owe you an apology. I took your time for just a mistake i made.

[Ibrahim harmankaya]

where n is something greater than 262144.

[Matt Fig]

No apology needed, it happens all the time to everyone. I was hoping that by demonstrating that FOR loops weren't clipped at the command line it would spur you to investigate further. Looks like it worked!

[Walter Roberson]

That code would fail because "=" cannot be used in the middle of an "if" statement.

[Ibrahim harmankaya]

Well, i wrote it wrong here. Of course it would. But it is == in my .m file. Or it would never work because of syntax error.

[Ibrahim harmankaya]

@Matt: Yes Matt, it happens sometimes. Thank you.

Answer 2

[Jan]

What exactly does "stops and quit" mean? Did you use the debugger to find out, which line causes the break? Just insert a "if i == 262144, disp('catch'); end" and set a break point on the disp line. Then step through the code line by line. It is impossible for us to guess, which command in which line is responsible.

Answer 3

[Matt Fig]

Hmm, something weird is going on. Can you verify that this works at the command line:

for ii = 1:512*512*100,jj = ii/2;end,jj*2==512*512*100

Also, in your loop is there a BREAK or RETURN statement anywhere?