MATLAB: How to execute a code if matlab turns busy while executing it.?

execution of a lengthy code in matlab

hi,
I am a beginner to matlab. I have written a function code for the implementation of Crank Nicolson Method within which i hv called a script named Compressibility as given below. But weneva i run this code matlab shows its busy…for a long time. When i press ctrl+C the cmmand window shows the execution was stopped by user at line 44..evrytime i press ctrl+c. the codes r given below. How can I run the program n get my desired output circumventing this problem??? Plzz plzz help!!
function [ P_out ] = Cranknicolson(H,L,D,T,dt,dx,I,N,Q_init,P_in,rho)
%



%
%parameters needed:
g = 9.81; %acc. due to gravity(m/s2)
%height of receiving end(m)=H
%Length of gas duct(m)=L
f = 0.003; %friction factor
%diameter of gas duct(m)=D
R = 392; %m2/(s2.K)
%Temperature(K)=T
%density of gas(kg/m3)= rho
%Initial flow=Q_init
%Input pressure=P_in
Z=1; %initial guess of Z value
compressibility;
c = sqrt(Z*R*T);% C is the iso-thermal speed of sound
r = sqrt(L.^2+H.^2);
Y = H/r; %value of sine(theta)
P_out = zeros(N,1);
A = zeros((I-1),(I-1));
C = zeros((I-1),(I-1));
G = zeros((I+1),N);
G1 = zeros((I-1),1);
G(1,:) = P_in.^2;
alpha = (16*f*Q_init)/(D.^3*c.^2*pi);
beta = (2*g*Y)/c.^2;
a = dt/(alpha*dx.^2);
b = (alpha*beta*dx)/2;
A1 = a-b;
A2 = -2*a-2;
A3 = a+b;
A4 = b-a;
A5 = 2*a-2;
A6 = -a-b;
for i=1:(I-1)
    A(i,i)=A2;
    C(i,i)=A5;
    while i>1
        A(i-1,i)=A3;
        A(i,i-1)=A1;
        C(i-1,i)=A6;
        C(i,i-1)=A4;
    end
end
for i=2:(I+1)
    x=(i-1)*dx;
    G(i,1) = (G(1,1)+(xi/sigma))*exp(-sigma*x)-(xi/sigma);
end
G1(1:(I-1),1)=G(2:I,1);
for n=1:(N-1)
    G(I+1,n+1)=(G(I,n)+(xi/sigma))*exp(-sigma*dx)-(xi/sigma);
    B = [ (A4*G(1,n) - A1*G(1,n+1));zeros(I-3,1);(A6*G(I+1,n) - A3*G(I+1,n+1)) ];
    G2 = A\((C*G1)+B);
    G1(1:I-1,1) = G2(1:I-1,1);
    G(2:I,n+1)=G2(1:I-1,1);
end
P_out(1:N,1)=sqrt(G(I+1,1:N));
end
**Compressibility**:
%To find out the value of Z(compressibility factor)
%
%parameters needed: 
Qn0 = 50; %initial flow(m3/s)
P_0 = 50e+5; %input pressure(pascal)
%Other values
r = sqrt(L.^2+H.^2);
Y = H/r;
%
Z0 = 1; %initial value
c = sqrt(Z0*R*T);
sigma = (2*g*Y)/c.^2;
xi = (f/D)*(((8*rho*c*Qn0)/(pi*D.^2)).^2);
    P_L = sqrt((P_0.^2 + (xi/sigma))*(exp(-sigma*L))-(xi/sigma));
    P_avg = 0.5*(P_0+P_L);
    Z = (1 - (P_avg/39e6));
while abs(Z-Z0)>1e-6
    Z0=Z;
    c = sqrt(Z0*R*T);
sigma = (2*g*Y)/c.^2;
xi = (f/D)*(((8*rho*c*Qn0)/(pi*D.^2)).^2);
    P_L = sqrt((P_0.^2 + (xi/sigma))*exp(-sigma*L)-(xi/sigma));
    P_avg = 0.5*(P_0+P_L);
    Z = (1 - (P_avg/39e+6));
end
fprintf('The value of Z is %f\n',Z)

Best Answer

Your code has
   while i>1
        A(i-1,i)=A3;
        A(i,i-1)=A1;
        C(i-1,i)=A6;
        C(i,i-1)=A4;
    end
but does not change "i" within the "while".
Perhaps you want "if" instead of "while"
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