How To Fix an Infinite Recursion?

I keep getting the following error when I run this code: "Out of memory. The likely cause is an infinite recursion within the program." It refers to this part of the code: "Error in AmericanPrice (line 4) P=AmericanPrice(0.08,0.12,0.2,100,50,10,300,3);" How can I fix this?

Update1: My bad, there was some typos in the code, it should be updated now! After entering the input arguments , i get this error "Undefined function 'find' for input arguments of type 'cell'. Error in AmericanPrice (line 32) bn=find(sign(diff(Pn)/dx+1)-1,1,{'last'})+bn;"

Update2: After changing "bn=find(sign(diff(Pn)/dx+1)-1,1,{'last'})+bn;" to "bn=find(sign(diff(Pn)/dx+1)-1,1,['last'])+bn;" i was able to get an output , im checking atm if it is the appropriate output

 function [P,b]=AmericanPrice(r,delta,sigma,K,nx,nt,Xhat,That)
%Usage:P=AmericanPrice(r,delta,sigma,K,nx,nt,Xhat,That)
%Example:P=AmericanPrice(0.08,0.12,0.2,100,50,10,300,3);
 dx=Xhat/nx;
dt=That/nt;
for i=1:nx-1
        A(i,i:i+2)=[((r-delta)*dt*i-sigma^2*dt*i^2)/2...
            1+r*dt+sigma^2*dt*i^2
            (-(r-delta)*dt*i-sigma^2*dt*i^2)/2];
end
P(:,1)=max(K-[0:dx:Xhat],0);

 if(delta==0)
    b(1)=K;
 else
    b(1)=min(K,K*r/delta);
 end

 for j=2:nt+1
    bn=0; run=1;
    while(run)
        An=[A(1+bn:end,1+bn:end)];
        An(end+1,end-1:end)=[-1 1];
        An(end+1,1)=1;
        Cn=[P(bn+2:nx,j-1)' 0 K-bn*dx]';
        Pn=inv(An)*Cn;
        if(Pn(2)<K-((bn+1)*dx))
            bn=find(sign(diff(Pn)/dx+1)-1,1,{'last'})+bn;
        else
            b(j)=bn*dx; run=0;
        end
    end
    P(:,j)=[K-[0:bn-1]*dx Pn'];
 end

Answer 1

[Image Analyst]

Make a file called test.m and put this in it (assuming you have R2016b or later):

P=AmericanPrice(0.08,0.12,0.2,100,50,10,300,3);

function P = AmericanPrice(input1, input2, input3, input4, input5, input6, input7, input8);
dx=Xhat/nx;
dt=That/nt;
for i=1:nx-1
  A(i,i:i+2)=[((r-delta)*dt*i-sigma^2*dt*i^2)/2
    1+r*dt+sigma^2*dt*i^2
    (-(r-delta)*dt*i-sigma^2*dt*i^2)/2];
end
P(:,1)=max(K-[0:dx:Xhat],0);

if(delta==0)
  b(1)=K;
else
  b(1)=min(K,K*r/delta);
end

for j=2:nt+1
  bn=0; run=1;
  while(run)
    An=[A(1+bn:end,1+bn:end)];
    An(end+1,end-1:end)=[-1 1];
    An(end+1,1)=1;
    Cn=[P(bn+2:nx,j-1)' 0 K-bn*dx]';
    Pn=inv(An)*Cn;
    if(Pn(2)<K-((bn+1)*dx))
      bn=find(sign(diff(Pn)/dx+1)-1,1,{'last'})+bn;
    else
      b(j)=bn*dx; run=0;
    end
  end
  P(:,j)=[K-[0:bn-1]*dx Pn'];
end
end

If you have an antique version of MATLAB you can't put that all into one file, so either have the first line be

function test()
P=AmericanPrice(0.08,0.12,0.2,100,50,10,300,3);
end

OR put this into test.m

P=AmericanPrice(0.08,0.12,0.2,100,50,10,300,3);

and the rest into an m-file called AmericanPrice.m

[K]

i have r2017a, i did update the code , there was some typos in there

[Image Analyst]

So it is working now?

[K]

yes i think so

Answer 2

[John D'Errico]

Is AmericanPrice the name of this function? If so, then it calls itself. Note the error message is:

"Error in AmericanPrice (line 4)
P=AmericanPrice(0.08,0.12,0.2,100,50,10,300,3);"

So, line 4 of the AmericanPrice function is a call to AmericanPrice. That will go on forever, therefore the infinite recursion.

[Star Strider]

I considered that.

I opted to explore the hypothesis that ‘run’ isn’t changing first, since we don’t know if the function is calling itself.

[K]

i updated the code , there was some typos

Answer 3

[Star Strider]

By your description, ‘run’ never changes. Since it appears that ‘bn’ is always going to be positive and increasing, one way to keep your while loop from becoming infinite (until you can determine what the problem is) would be to change the while condition to include a limit on ‘bn’:

      while(run | (bn < 1E+3))

Remember not to use the ‘short circuit’ operator or the ‘bn’ test will never execute.

Note — This is UNTESTED CODE. You will have to test it.

[K]

so you dont know what the problem is ?

[Star Strider]

No.

I’m not sure what you’re doing, how your code is supposed to work, or what you’re calculating. All I did was to include a ‘fail-safe’ so you can figure out what the problem is. When the ‘fail-safe’ stops your code, you’ll have access to the values of all your variables, so you can see what they are.

You’re the only one who actually can troubleshoot your code and see what isn’t working correctly.

If you can’t figure it out otherwise, use the debugger to understand what your code is doing and what your variable values are between iterations.

[K]

i tried your failsafe it gave me the same error.

[Star Strider]

Put a lower threshold on ‘bn’ and see what the result is:

while(run | (bn < 1E+1))

Either ‘run’ isn’t being toggled, or we’re only seeing part of your code, and as John mentioned, your function is calling itself.

[Star Strider]

Definitely a typo here:

bn=find(sign(diff(Pn)/dx+1)-1,1,{'last'})+bn;
                                   ↑ ← DON’T USE A CELL STRUCTURE HERE

Try this instead:

bn = find(sign(diff(Pn)/dx+1)-1,1,'last')+bn;