How can I make my loop works?

How can I make my loop works?

I know P0 (my initial guess)

P0 =

    3.5378   -2.3325
   -2.3325    3.5378

 X =

    1.2448   -0.4685
   -0.4685    1.2448

Hcore =

   -1.1204   -0.9583
   -0.9583   -1.1204

g(1,1,1,1) = 0.7746 g(2,2,2,2) = 0.7746 g(1,1,2,2) = 0.5697 g(2,2,1,1) = 0.5697 g(2,1,1,1) = 0.4441 g(1,2,1,1) = 0.4441 g(1,1,2,1) = 0.4441 g(1,1,1,2) = 0.4441 g(2,2,2,1) = 0.4441 g(2,2,1,2) = 0.4441 g(2,1,2,2) = 0.4441 g(1,2,2,2) = 0.4441 g(2,1,2,1) = 0.2970 g(1,2,2,1) = 0.2970 g(1,2,1,2) = 0.2970 g(2,1,1,2) = 0.2970

and I am trying to find a P1 when

(2.^-2).*(P1(i,j)-P0(i,j))^2)^(1/2)) < 10^-7.

My loop should use P0 to find a new P1, and then P0 becomes P1, when it tries to find another P1 again...until the criteria is satisfied.

for i=1:2
    for j=1:2
while (((2.^-2).*(P1(i,j)-P0(i,j))^2)^(1/2)) < 10^-7  %convergence criteria
    for i=1:2
    for j=1:2
        for k=1,2
            for l=1,2
                F1 = Hcore + (P1(i,j)).*(g(k,l,j,i) - 0.5.*g(k,i,j,l))
                Ft1 = (ctranspose(X))*F1*X
                [Ct1, Dt1]=eig(Ft1)
                C1 = X*Ct1
                P1 = 2.*C1*(ctranspose(C1))
            end
        end
    end
    end
end
    end
end

[Stephen23]

Your initial value P0 never gets referred to inside the loop. Fix this, and you probably fix the problem.

Note: you should avoid using i and j as the names of variables, as these are the names of the inbuilt imaginary unit . Accidental overloading of inbuilt functions and variables can cause all sorts of hard-to-diagnose problems...

Answer 1

[Image Analyst]

I don't see P0 mentioned inside your while loop at all. I don't even see where P0 is initialized. But I'm sure this will solve the problem: http://blogs.mathworks.com/videos/2012/07/03/debugging-in-matlab/

[Anderson]

Hi, my P0 is

P0 =

    3.5378   -2.3325
   -2.3325    3.5378

But my loop does not go further to compute others P1 until the criteria convergence is satisfied.

I watched the video, but I still did not find the problem.

   Thank you!

[Image Analyst]

See this http://www.mathworks.com/matlabcentral/answers/13205-tutorial-how-to-format-your-question-with-markup

And attach your m-file and any data files it reads in with the paper clip icon so people can actually run it and debug it for you.

And you said "should use P0 to find a new P1". So tell me, in that loop, does P0 ever go into any calculation of a new value for P1? Not as far as I can see.

[Anderson]

Thank you for your help!

I attached the file to my question. Yes, P0 is a guess matrix used to compute P1. After that I try to use P1 to find another P ... until the convergence criteria is satisfied.

[Iain]

If P0 is setup before the loops start, and you're using the check "(((2.^-2).*(P1(i,j)-P0(i,j))^2)^(1/2)) < 10^-7", then what you're checking for is P1 is being approximately equal to the very original P0, and not the immediately prior P0.