this is code of 2D reaction diffusion equation using ADI method the code works well when i use the exponential

i am doing finite difference scheme to solve Fisher kpp equation :$u_{t}=u_{xx}+u_{yy}+u-u^2 and with initial condition u(x,y,0)=1 for (x,y)=(0,0)and 0 other wise and u=0 at boundary ,also plot showing the positions where u(x, y, t) = 0.5 for each time step .

i try to solver $u_{t}=u_{xx}+u_{yy}+u-u^2 in(-a,a)times(-b,b)times(0,T)with initial condition u_0=1 if(x,y)=0and 0 other wise and u=0 in$partialomega$ where $omega=[-a;a]times[-b;b], i do that by finite difference method

Reduced differential transform method