My MATLAB loop is not ending

So for studying, I made the following loop, but the thing is it not ending. I think it's something wrong with the code, please help

clc;
clear all;

 
time    =   1   ;
t_star  =   0;
%Concentration
Cf(time)      =   1; 
Cd(time)      =   2; 
%Volume
Vf0      =   2;
Vd0      =   2;
%Assume 298K temperature
L       =   0.077;          %Channel Length in metre
W       =   0.026;          %Channel width in metre
H       =   0.003;          %Channel height in metre
%Cross-Flow Velocity
vf      =   0.085;
vd      =   0.085;
A       =   3.08e-12;       % Pure water permeability coefficient A in m/Pas
% B is negligible
S       =   3.6e-04;        %Structural Parameter of Membrane in m
Am      =   0.014;          %Area of Membrane in m2

dh      =   (2*W*H)/(W+H);  %Hydrawlic Diameter in m

Cf0 = 1;
x2_pif  =   42.6;
x3_pif  =   7;  
Pi_f0    =   (x2_pif*Cf0 + x3_pif*Cf0^2)*10^5; 

%Cf(time)    = 0;
%Cd(time)    = 3;

%Cf_new(time) = 0;
%Cd_new(time) = 3;

while(time >= 1) 

%Viscosity of FS in Pas
x1_muf  =   890.7;
x2_muf  =   70;
x3_muf  =   1.75;
mu_f    =   (x1_muf + x2_muf*Cf(time) + x3_muf*Cf(time)^2)*10^-06;

%Density of FS in kg/m^3
x1_rhof =   996.845;
x2_rhof =   40.5;
rho_f   =   x1_rhof + x2_rhof*Cf(time);

%Diffusivity of FS in m^2/s
x1_df   =   1509;
x2_df   =  -94;
x3_df   =   -6;
D_f     =   (x1_df + x2_df*Cf(time) + x3_df*Cf(time)^2)*10^-12;

%Schmidt Number of FS
Sc_f    =   mu_f/(rho_f*D_f);

%Reynolds Number of FS
Re_f    =   (rho_f*vf*dh)/mu_f;

%Sherwood Number for FS as Reynold Number less than 2100
Sh_f    =   1.85*(Re_f*Sc_f*(dh/L))^0.33;

%Mass Transfer coefficient of FS
k_f     =   (Sh_f*D_f)/dh; 

%Diffusivity of DS in m^2/s
x1_dd   =   1509;
x2_dd   =  -94;
x3_dd   =   -6;
D_d     =   (x1_dd + x2_dd*Cd(time) + x3_dd*Cd(time)^2)*10^-12;

%Mass Transfer coefficient of DS
k_d     =   S/D_d; 

%Osmotic Pressures of FS and DS
x2_pif  =   42.6;
x3_pif  =   7;  
Pi_f    =   (x2_pif*Cf(time) + x3_pif*Cf(time)^2)*10^5;     %Osmotic Pressure of FS

x2_pid  =   42.6;
x3_pid  =   7;  
Pi_d    =   (x2_pid*Cd(time) + x3_pid*Cd(time)^2)*10^5;     %Osmotic Pressure of DS


syms Jw
eqn     =   Jw - A*(Pi_d*exp(-Jw*k_d)-Pi_f*exp(Jw/k_f)) == 0;
solJw   =   double(vpasolve(eqn, Jw));

%number of water moles transport fr om the FS side to the DS side

Mw      =   18; %molar mass of water in grams/mol
xf_wat  =   (Cf(time)*Mw)/rho_f;
n       =   ((solJw*Am)*(rho_f*xf_wat)/Mw)*1000;

t_star  =   t_star + n;
%the number of water moles in the FS and DS sides

m_f     =   ((Vf0)*(rho_f*xf_wat)/Mw) - t_star ;

%Density of DS in kg/m^3
x1_rhod =   996.845;
x2_rhod =   40.5;
rho_d   =   x1_rhod + x2_rhod*Cd(time);

xd_wat  =   (Cd(time)*Mw)/rho_d;

m_d     =   ((Vd0)*(rho_d*xd_wat)/Mw) + t_star ;

%the new volume of FS and DS sides

Vf_new  =   Vf0 - ((t_star*Mw)/(rho_f*xf_wat));
Vd_new  =   Vd0 + ((t_star*Mw)/(rho_d*xd_wat));


%the new concentration of FS and DS

Cf_new(time)  =   (Cf(time)*Vf0)/Vf_new;
Cd_new(time)  =   (Cd(time)*Vd0)/Vd_new;
 
%if(D_f==D_d)
 %   time =0; 
%else time = time+1;
 %   Cf(time)    =  Cf_new(time-1);
   %Cd(time)    =  Cd_new(time-1);  
%end
    
  if ( Cf_new(time) ~= Cd_new(time))
     time = time + 1 ;
     Cf(time)    =  Cf_new(time-1);
     Cd(time)    =  Cd_new(time-1);
  elseif ( mod(Cf_new(time) - Cd_new(time))<=0.5)
      Cf_final = Cf_new(time);
      Cd_final = Cd(time);
      time = 0;
  end
 end
 
 
 

     

Answer 1

[Cris LaPierre]

Either your 'if' condition at the end of your while loop is always true, or your 'elseif' condition is never true. I would try to rethink that part of your code.

[Steven Lord]

In particular, comparing floating-point numbers for exact, down-to-the-last-bit equality (or inequality) may not be what you want. If you want to stop when the two quantities Cf_new and Cd_new are "close enough" compare with a tolerance.

if abs(Cf_new(time) - Cd_new(time)) < some_tolerance
    % you're done
else
    % you're not done
end

[Ajmal R S]

Yes , thank you I was looking for modulus subtraction, so I changed the code with conditional OR operator. Even now the loop is not ending. But I think I made a mistake in the logic somewhere and not a problem with the code itself

[Cris LaPierre]

I suggest learning to use the debugger. It sounds like you need to explore your values in order to develop the necessary logic.