Memory during a loop

Hi,

If I run Clear All during a loop, will it also clear the loop value?

Thanks,

[Aadil]

ok it seems it does, is there any way round this, I'm reading large .mat data files, any way to only clear them and not the previous variables?

Answer 1

[Jan]

As usual I mention, that clear all removes all loaded functions from the memory and reloading them from the disk and parsing them wastes a lot of time. When you want to clear variables, use

clear variables

However, Arthur's hint to use S=load() is very good. 1. it is easy to clear, 2. you cannot overwrite local variables by accident (as e.g. the loop counter...), 3. The debugging is much easier, because you can see on first sight, that "S.abcde" comes from the loaded file, and 4. Matlab is much faster with fixed names of variables compared to the ones created dynamically by EVAL or LOAD without catching the output.

[Aadil]

hmm ok

so if I have:

for WhichVehicle = 1 : length(ProcessedFolderDirectories)

load(blahblah.mat)
run(blahblah)

clear variables

end

So it will only clear the variables then?

Answer 2

[Arthur]

sure, you can just clear the variable:

clear varname

check:

   doc clear

[Aadil]

but the .mat files contain 400 variables

[Arthur]

Do you need to load all the variables at once? You can also load a single variable at the time.

S = load(filename, variables)

This can be more memory efficient, but you may have to open the file multiple times...

[Jan]

+1. Especially the suggested "S=load()" is a very good idea.

Answer 3

[Sean de Wolski]

It depends on where you call it, compare:

• 1

for ii = 1:10
  ii
  clear all
end

• 2

for ii = 1:10
  clear all
  ii
end

But of course Arthur is right - you shouldn't need to use clear all at all.

[Aadil]

is there any way to clear the last mat file loaded?

[Sean de Wolski]

Assign the *.MAT file you load to a variable then clear it when you're done. That way you aren't poofing variables into your workspace.

for ii = stuff
 S = load('mymatfile.mat');
 do_stuff_with(S)
 clear S
end