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Mohamed G. Gouda					CS356
Spring 2008                                             Midterm 3 Solution
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1. (10 points)

process p

inp   N     : set {g | p[g] is a neighbor of p[i]},
      up    : array [N] of boolean
var   ts,t  : integer,                          {init. 0}
      h     : N
      txt   : integer                         
      d     : 0..1
par   g     : N

begin
      rcv data(t,txt,d) from p[g]  -->
          if t <= ts -> skip
          [] t >  ts -> ts := t;
                        if (i mod 2 =  d) -> {accept txt} skip
                        [] (i mod 2 != d) -> {ignore txt} skip
                        fi
                        h := NEXT(N, g);
                        do h != g ->
                           if up[h] ^ h != 0 ->
                              send data(t, txt, d) to p[h]
                           [] ~up[h] v h = 0 -> skip
                           fi;
                           h := NEXT(N,h)
                        od
          fi                  
end

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2. (10 points)

rtb[0, 0..1] in p[0] = 1, 2
rtb[0, 0..1] in p[1] = 0, 2 or 0, 0
rtb[0, 0..1] in p[2] = 0, 0 or 0, 1
rtb[0, 0..1] in p[3] = 1, 2
rtb[0, 0..1] in p[4] = 2, 3

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