Why Matlab slows down dramatically after a few iterations in my code?

Hello everyone and thanks for your help.

I wrote below simple function and by using a for loop, I call this function to calculate a 200-by-200 matrix and then write it in a file. When I run it, it works fine for about 100 iterations. But after that, my computer is slowed down dramatically and afterwards, in each iteration this slowness is worsen.

It seems the speed decreases exponentially. In other words, for first iteration, it takes less than 1 second but after 150 iterations, each iteration takes more than 1 minutes. I used 'memory' and found out that Matlab pre-allocated about 4GB.

I tried to use 'clear' to clear all variable in each iteration in order to free memory without success.

Any help is appreciated.

imgs = @(c,fnt) rgb2gray(insertText(ones(200, 200, 3), [1 1], char(c), ...
                                             'Font', fnt, ... 
                                             'FontSize', 195, ... 
                                             'AnchorPoint', 'Center', ...
                                             'TextColor', [0 0 0], ...
                                             'BoxOpacity', 0) ...
                                 ) > 0.55; 

for char1=1:100
    for ii=1:100
         L=imgs(char1,fnt{ii});
         L=L(:)';
         StoreFile(L); % a function to write data to a file
         clear L;
    end
end

[Image Analyst]

What are you trying to do? Why does your function "imgs" take one argument, c, and you're tying to pass in 6 arguments, (200,char1,'Sanserif2',200,85,89), to it?

[david jones]

Sorry, you are right. EDITED

[per isakson]

Did you

• use Windows Task Manager (or similar tool) to see if the memory usage increases. (I don't see why it should.)
• use Profile to Improve Performance

[José-Luis]

Could you show what StoreFile does? Are you closing the file you generate after each iteration?

[david jones]

The StoreFile gets a matrix name 'L' (size of 128 that is an image containing a character) and then open a file, write L and close it. That's all.

[per isakson]

I made an experiment, but failed to reproduce the behavior you see. I saw no slow down.

Non-printing characters caused me a bit of problem so I excluded them. "then open a file, write L and close it" does that mean ONE file or one file per image? I appended to ONE text file, which I thought was the worse case.

Proposal: Upload an executable code that demonstrates the behavior.