flight scheduler - SV randomization

 Q. How many combinations can be there for the below scenario?

There are 3 flights and 8 passengers (a,b,c,d,e,f,g,h) 

1.a and b should always be together 

2. each flight needs to fly . minimum passengers that can go in an flights are = 1 , 

Maximum passengers that can go in an flights are = 4 .

Answer : 

Instaed of manually thinking of all scenarios , we can write in in system verilog . (using constarints) .

1. create an enum of passengers 

 typedef enum {a,b,c,d,e,f,g,h} passenger ;

2. create a queue called flight like this :

    passenger flight[]; 

// Code your testbench here

// or browse Examples

class FlightScheduler;

  // Passenger list

  typedef enum {a, b, c, d, e, f, g, h} passengers_t;

  // The flights array stores the flight allocation for each passenger

  rand passengers_t flights[8]; // Array of flight assignments for 8 passengers

  rand int flight_count[3];     // Number of passengers on each flight (0, 1, 2)

  constraint flight_constraints {

    // Each passenger must be assigned to one of the three flights

    foreach (flights[i]) flights[i] inside {0, 1, 2};

    // Ensure passengers 'a' and 'b' always travel together

    flights[0] == flights[1]; // Both passenger a and b travel on the same flight

    // Count how many passengers are on each flight

    foreach (flight_count[i]) {

      flight_count[i] == (flights.count(i)); // Count passengers in flight i

    }

    // Each flight must have between 1 and 4 passengers

    foreach (flight_count[i]) flight_count[i] inside {[1:4]};

  }

  // Display the flight assignments

  function void display_flight_allocation();

    $display("Flight assignments:");

    foreach (flights[i]) begin

      $display("Passenger %0d -> Flight %0d", i, flights[i]);

    end

    $display("Flights distribution: Flight 0: %0d, Flight 1: %0d, Flight 2: %0d",

             flight_count[0], flight_count[1], flight_count[2]);

  endfunction

endclass

// Testbench

module tb_flight_scheduler;

  initial begin

    FlightScheduler scheduler = new();

    if (scheduler.randomize()) begin

      scheduler.display_flight_allocation();

    end else begin

      $display("Failed to randomize!");

    end

  end

endmodule

Q.  3*3 Array question :

class A ;

  rand int mem[3][3];

  constraint c1{ 

      unique{mem}; 

    foreach(mem[i,j]) 

    {

      mem[i][j] inside {[1:9]}; 

    }

  };

    

  constraint c2{

    foreach(mem[i])

    {

      foreach(mem[k])

      {

        mem[i].sum() == mem[k].sum();

      } 

    }

  };

      

  constraint c3{

    foreach(mem[,j])

    {

      foreach(mem[,k])

      {

        mem.sum() with (mem[item.index][j]) == mem.sum() with (mem[item.index][k]);

      } 

    }

  }; 

  

endclass

module t();

  A a_h ;

  initial begin

   a_h = new ; 

      a_h.randomize();

      $display("value is %p", a_h.mem); 

   end 

endmodule