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Mohamed G. Gouda                           CS 356
Fall 2005                                  Solution to Midterm 2 
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1.

process p

inp m                    { m>0 }
var conp    : boolean,   { initially, false }
    cansnd  : 0 .. m,
    with    : 0 .. n-1
par i       : 0 .. n-1

begin
   timeout ~conp ^ (#ch.p.q[i]+#ch.q[i].p=0) -> send crqst to q[i]

[] rcv crply from q[i] -> if  conp    -> send drqst to q[i]
                          [] ~conp    -> conp,cansnd,with := true,m,i
                          fi

[] conp                -> if cansnd>0 -> send data to q[with];
                                         cansnd := cansnd -1
                          [] true     -> send drqst to q[with];
                                         cansnd := 0
                          fi
                            
[] rcv drply from q[i] -> if with =i  -> conp := false
                          [] with!=i  -> skip
                          fi
end

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2. 

length of longest elementary corruption burst that can be 
detected =

   if n = 1 -> 1
   [] n > 1 -> (m+1)*n  
   fi

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