CS684 Spring 2023

PROBLEM STATEMENTS

Q1.

Consider the following node display discussed in class.

node display(updown:bool) returns (o,q:int)
var
    last z: int = 20;
    y:int;
let
  q = z;
  switch updown
  | true  do  y = 100 -> pre(y)+1; 
                         z = (last z) + 1;
                         o=y + z
  | false do  y = 10  -> pre(y)-1;
                         z = (last z) - 1;
                         o=y + z
  end
tel

What will be the values of output flows o and q for the input flow

• updown = 0 0 1 1 1 0 1 0 0 1 1 1

Answer format: Create q1 text file. List the output values of "o" in first line and q in second line in comma-separated format.

Q2.

Consider the following node which is a variant of the node discussed in the class. The change is that the transitions are of then type here instead of the continue type as shown in class. Hence the behaviour of the automaton differs.

Complete the table below giving the output of this node for the first 11 cycles in a table. Also give the start state (ST) and then next state (NS) for each of these cycles.

node myautomaton() returns (y:int; stup:bool; v:int)
var last x:int = 2;
let
    y = x; 
    automaton
        state Up
                 var w:int; 
                 do x = (last x) + 1; stup = true;
                    w = 0 -> pre(w)+1; v=w;
        until  x >= 5 then Down
        state Down
            var w:int;
            do x = (last x) - 1;  stup = false;
            w = 50 -> pre(w)-2; v=w;
        until x <= 3 then Up
    end
tel

Answer format: Create q2 text file. List the values for 11 cycles in comma-separated format. Make sure to write each expression's value for 11 cycles on a separate line.

Q3.

Consider the following node. Complete the table below giving the output of this node for the first 10 cycles in the table. Also give the start state (ST), active state (AS) and then next state (NS) for each of these cycles.

node myautomaton(c: bool) returns (o: int; stup:bool)
 let
    automaton
      state Up
         do o = 60 -> pre(o)+2; stup = true;
      unless c continue Down
      state Down
         do o = 150 -> pre(o)-2; stup = false;
      until c then Up
    end
 tel

Answer format: Create q3 text file. Without using a space, list the values for 10 cycles in comma-separated format. Make sure to write each expression's value for 10 cycles on a separate line.

Q4.

Consider the node myautomaton given below. Try to understand its structure. How many distinct modes does it have? Explain how you came up with this number.

node myautomaton(i1: bool; i2: bool; i3: bool; i4: bool)
  returns (o1: bool; o2: bool; o3: bool; o4: bool)
let
  automaton
    state State1
      do o1 = false; o2 = false; o3 = false; o4 = false
      until i1 then TMP12
      unless i2 then TMP11
    state TMP11
      do o1 = false; o2 = true; o3 = false; o4 = false;
      until true then State3
    state TMP12
      do o1 = true; o2 = true; o3 = false; o4 = false;
      until true then State2

    state State3
      var last end1: bool = false; last end2: bool = false;
      do o1 = false; o2 = false; o3 = false; o4 = false;
         automaton
           state State1_1
             do until i3 then State2_1
           state State2_1
             do end1 = true;
         end;
         automaton
           state State1_2
             do unless i4 then State2_2
           state State2_2
             do end2 = true
         end
       until end1 & end2 then State1
       unless i1 then State4
          |   i2 then State2

    state State2
       var l1: bool;
       do o1 = false; o2 = false; o3 = false; o4 = l1; l1 = true;
       until i4 then State4

    state State4
       var l2: bool;
       do o1 = false; o2 = false; o3 = l2; o4 = false; l2 = true;
       until i4 then State1
    end
tel

Answer format: Create q4 text file. Mention number of modes in first line and explanation in second line.

Q5.

Consider the following controller for farm road crossing. Try to understand its working. Try to simulate it using Heptagon simulator.

A farm road (or side road) crosses a main road. Traffic light controller must turn on or off the lights maingreen, mainred, sidegreen, sidered. An input “carwait” is true if a car is waiting on the farm road. Input “second” is the timer input which becomes true for one clock cycle every one second. Thus the count of “second” gives how much time has elapsed.

node traffic(carwait,second:bool) 
      returns (maingreen, mainred,sidegreen,sidered:bool)
var timegreen:int;
let
  automaton
    state Maingreen
       do  timegreen = 180 -> if (((pre(timegreen)) > 0) and second) then 
                                    pre(timegreen)-1  else pre(timegreen);
       
           maingreen = true; mainred = false;
           sidegreen = false; sidered = true;
       until ((timegreen <= 0) and carwait) then Sidegreen
    state Sidegreen
       do
           timegreen = 60 ->
                if (((pre(timegreen)) > 0) and second) then pre(timegreen)-1
                           else pre(timegreen);
           maingreen = false; mainred = true;
           sidegreen = true; sidered = false;
       until ((timegreen <=0)  and not carwait) then Maingreen
  end
tel

1. Modify the above controller by adding outputs “mainyellow and sideyellow. The aim is that traffic light must remain yellow for 10 seconds before turning red.

2. What are some of the requirements over the traffic node? For example, one simple requirement is that at most one of maingreen and sidegreen can be true in any clock cycle. List as many requirements (written in English) as you think are appropriate for the modified controller you have designed in part (1).

Answer format: For question 5.1, submit q51.ept file. And for question 5.2, create q52 text file and mention different requirements in separate lines.

Q6.

Model a Gas Burner Controller as a Heptagon node (Code required)

node controller(flame: bool; sec: bool) returns (gas: bool; spark: bool)

to meet the following requirements. Preferably Use the automaton construct.

“Controller keeps gas on/off using the output gas and strikes a flame using the output spark. It can detect whether flame is on/off using input flame. Flow sec is a second beacon. It is true at each clock cycle where one second has elapsed since the previous such value. Flame will not occur unless the gas has accumulated for at least 15 seconds. Not every spark results in flame. Flame also occasionally goes off due to wind. Making a spark after Gas has leaked for more than 60 seconds causes an explosion. Hence, after a leakage longer than 60 seconds, the Gas must be turned off and allowed to dissipate for 120 seconds to reach a safe state. The controller should try to keep the flame on as much as possible.”

Please explain your design. Simulate your code using the Heptagon simulator for various sample inputs and submit the output produced.

Answer format: Submit q6.ept. Explain your design in comments in code file.

Submission Instructions

• Create a folder named <RollNo>_assignment3.
• Copy and paste all the files which has to be submitted inside the newly created folder according to the structure as shown below:

<RollNo>_assignment3
│  
└─── q1 (text file)
│  
└─── q2 (text file)
│  
└─── q3 (text file)
│  
└─── q4 (text file)
│
└─── q5
│   │   q51.ept 
│   │   q52 (text file)
|  
└─── q6.ept

Note: Folder name and file name should be same as mentioned in the above structure.

• Compress the folder in a .tar.gz file and submit it on moodle.