any suggestions to make this code faster

hi,

any suggestions to make this code faster, where if take just noofusers 50, it take three or more to complete:

%%%%%%%%%%%%%%%%%%%%%
targetdir = 'd:\matlab11\r2011a\bin\training_set';

nofusers=480189;

targetfiles = '*.txt';

fileinfo = dir(fullfile(targetdir, targetfiles));

f5=fopen('matlab11\r2011a\bin\netflix\un1-17.txt');

z5=fscanf(f5,'%d');

fclose(f5);

for j=1:nofusers

      k=1;

      for i = 1:17770

       thisfilename = fullfile(targetdir, fileinfo(i).name);

    f = fopen(thisfilename,'r');

     c = textscan(f, '%f %f %s', 'Delimiter', ',', 'headerLines', 1);

     fclose(f);

      c1 = c{1};    a=find(c1==z5(j));

     if ~isempty(a)

         c3=c{3};

       format long
      dat=round(datenum(c3,'yyyy-mm-dd'));

     array(j,k)=i;

     array(j,k+1)=dat(a);

     k=k+2;

     else
         continue;
     end; end; end;

thanks for any advice

[Daniel Shub]

@huda, Please combine this question with your other similar question.

Answer 1

[Daniel Shub]

You should preallocate array to the correct size before the loop. It looks like you could also use a parfor for the first loop. You don't need "format long" in the inner loop (or at all). There are much faster things than datenum (have a search on this site).

[huda nawaf]

is preallocate make the code faster ?

if I know just the no. of rows , can do for ex. array(1:100,:)=0?

thanks

[Daniel Shub]

In the past, preallocation can considerably speed up code. r2011a is supposed to be better without preallocation, but I haven't tested it and have seen rumors that it is not. I think preallocating the rows will help. Currently, you increase the number of columns by 1, whenever you exceed the current number of columns. You can block allocate and increase it by 10, 100, 1000 ... This will also help speed things up

[huda nawaf]

hi,

please , I did not understand what u mean y this:

Currently, you increase the number of columns by 1, whenever you exceed the current number of columns. You can block allocate and increase it by 10, 100, 1000 ... This will also help speed things up

I hope to give me more details

thanks