Faster than for loop?

I presently have this code which tests a paricular function which I created _ _ [y n] function_gen1pdf1(a,b,c) _ _ for N times. Now this works fine up to N=100. However, I want it to work for N=100,000 but it's taking much too long to compute. Is it possible to vectorize it or make it work faster? Any suggestions are much appreciated!

N=100000;
y=zeros(N,1);
n=zeros(N,1);
for i=1:N; %testing the function for 100000 times
    [y(i) n(i)]= function_gen1pdf1(2,3,0.5); %The function being tested
end

[Star Strider]

Please post the function code!

[Stephen23]

"Is it possible to vectorize it": this depends entirely on the function function_gen1pdf1. If you want help trying to vectorize this, then you have to upload its code too.

[Geoff Hayes]

rox - I don't understand the line

 [y(i) n(i)]= function_gen1pdf1(2,3,0.5);

You keep calling function_gen1pdf1 with the same set of inputs for every i. Why is the code repeating the same call at every iteration of the for loop?

[Tapan]

I will echo everyone else's comments - you need to provide the function code. Perhaps try a parlor loop in the meantime.

[Jan]

@Geoff: The "gen" in the name might mean a genetic algorithm, such that random effects can be the reasn for different results inspite of the same inputs.

[Image Analyst]

Or maybe it generates a PDF document, or generates a probability distribution function. Whatever it does, apparently PDF does not mean "Pretty Darn Fast".

[Jan]

@rox: While the "function_" in the name of your function is pretty meaningless, "gen1pdf1" catches our interest.

Answer 1

[Image Analyst]

It's your function, it's not the for loop. If you just run a for loop 100,000 times it takes 0.2 milliseconds.

I tried it:

tic
for k = 1 : 100000
  ;
end
toc

Elapsed time is 0.000219 seconds.

So it if takes a long time, it's due to your function_gen1pdf1() function.

[rox]

I guess the problem is that function_gen1pdf1(2,3,0.5) calls yet another function inside it (as it is based on the rejection method) which contains fplot. Now I was experimenting and just tried working it out without the fplot, and it's much much faster! Thanks for your clarifying that the problem was with the function itself!

[Image Analyst]

rox, you're welcome. Does that mean that you can now mark the answer as "Accepted"?

[rox]

Yes, thanks!