CS706 Fall 2009

Practice Problem:

   The following diagram shows a computation of processes P, Q, and R
   using asynchronous communication. The messages in this computation
   are P1 --> Q1, R1 --> Q2, Q3 --> P2, P3 --> Q4, and R2 --> Q5.

       P  -P1--------------P2---P3------------>
            \              /\     \
             \             /       \
              \           /         \
              \/         /          \/    
       Q  ----Q1---Q2---Q3----------Q4---Q5--->
                  /\                     /\
                  /                      /
                 /                      /
                /                      /
       R  -----R1--------------------R2------>

  a. Determine the integer timestamp of each event in the above 
     computation.
      IT(P1)=     IT(P2)=      IT(P3)=
      IT(Q1)=     IT(Q2)=      IT(Q3)=      IT(Q4)=     IT(Q5)=
      IT(R1)=     It(R2)=

  b. Determine the vector timestamp of each event in the above 
     computatation. Each vector timestamp has three elements,
     with the first, second, and third elements indicating 
     logical clock values for P, Q, and R, respectively.

      VT(P1)=     VT(P2)=      VT(P3)=
      VT(Q1)=     VT(Q2)=      VT(Q3)=      VT(Q4)=     VT(Q5)=
      VT(R1)=     Vt(R2)=

  c. Indicate all events that are concurrent with P3.

  d. Indicate all events that are concurrent with R2.