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Mohamed G. Gouda                     CS 356
Fall 2005                            Solution to Midterm 1 
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1.

process p[i:0..2]
inp N : set{j | j is i +3 1 or i +3 2} 
var ready : 0..2  {initially,2}
par j : N

begin
   ready = 2          -> send rqst to p[i +3 1];
                         send rqst to p[i +3 2];
                         ready := 0
[] rcv rply from p[j] -> ready := ready + 1
[] rcv rqst from p[j] -> send rply to p[j] 
end

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2. 

G  : (st=1 v st=3) ^ (#ch.u[i].c + ch.c.u[i] = 0)


S  : if st=1 -> send rqst to c
     [] st=3 -> send rls to c
     fi


S' : if usr=i  -> avail := true;
     [] usr!=i -> skip
     fi;
     send ack to u[i]      

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