LDPC s-function to calculate PER

I was working on a project to investigate the performance of LDPC code in WSN. I'm running the project by using MATLAB Simulink. Hence, I had written a s-function to calculate the Packet Error Rate where any 1 bit of error in a packet will be considered as 1 PER. Unfortunately, my s-function block is not working properly but i couldnt spot where is my mistake. I hereby paste the my program down here. Can anyone please kindly correct me? For your information, there is a 2-bit delay in the block.

long i=0,j=0, PE=0;

if (temp != u1[0] && last_PE != 1) { BER++; PE=1; }

last_PE = 0;

for ( i=0; i<81; i++) { for ( j=0; j<400; j++) { if (u0[i*400+j]!=u1[i*400+j+2]) { BER++; PE=1; }

    }
    if (PE==1) 
    {
        PER++;
        PE=0;
    }

}

i=81; for ( j=0; j<399; j++) { if (u0[i*400+j]!=u1[i*400+j+2]) { BER++; PE=1; last_PE = 1; } } /* to compare the last bit of the last packet,if there is an error, BER increase and PE=1*/ temp= u0[i*400+399]; /* to store the last bit temporary for comparison later on*/

if (PE==1) { PER++; PE=0; }

y0[0]=BER; y0[1]=PER;