# Why while end error does not work in my code??

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esat gulhan on 26 Aug 2020
Commented: esat gulhan on 26 Aug 2020
clear clc
L=0.02;H=40;dx=0.01;dy=dx;dt=15
nx=uint32(L/dx+1);ny=uint32(H/dy+1);rx=dt/dx^2;ry=dt/dy^2;
k=28;alfa=12.5*10^-6;g=5*10^6;Ts=30;h=45
[X Y]=meshgrid(linspace(0,L,nx),linspace(0,H,ny));Tint=200;T=Tint*ones(ny,nx);
Tleft=0;Tright=Tint;Ttop=Tint;Tbottom=Tint;
T(:,1)=Tleft;T(:,end)=Tright;T(1,:)=Ttop;T(end,:)=Tbottom;Fo=alfa*dt*(dx^2);
time=0;n=time/dt;
err=1
tol=10^-1
while err>tol
n=n+1
Tn=T;
for i=2:nx-1
for j=2:ny-1
T(j,i)=Tn(j,i)+((Tn(j,i+1)+Tn(j,i-1)+Tn(j-1,i)+Tn(j+1,i)-4*Tn(j,i))+g*dx^2/k)*Fo
T(j,end)=Fo*((g*dx^2)/k - (2*h*(Tn(j,end) - Ts)*dx)/k - 2*Tn(j,end) + 2*Tn(j,end-1) + Tn(j,end)/Fo)
end
end
err = max(max(abs(Tn - T)))
end
İt is weird situation. My code is working but it does not stop. My error is smaller than 10^-2 but it does not stop.
Rik on 26 Aug 2020
On my copy of Matlab it does stop. To massively increase the speed of the code I did put semicolons in the inner loop.

Rik on 26 Aug 2020
Based on your now deleted comment ("Yeah, when i put semicolons it worked."):
The cause of the loop seeming to be stuck is that you printed the entire T array to your command window. This is fast, but it does take time. By putting semicolons in your code to suppress the output you avoid this, so the for loops finish in a reasonable time.
esat gulhan on 26 Aug 2020
well, at least with semicolons i can reach my aim. thanx anyway