System verilog constraints interview question involving multiple variables

 

Sequence item is as follows:

rand unique_bit 

rand num_of_reqs;

rand Bit [10:0] x [];

rand Bit[10:0] y[];

rand Bit [10:0] width[];      

rand Bit [10:0] height[];

rand bit [10:0]  frame_width;

rand bit [10:0]  frame_height;

 

Conditions for constraints.....

1. each request is combination of x,y, width & height

2. x+width must be less than or equal to frame width

3. y+height must be less than or equal to  frame height

4. if unique bit is set , combination of x,y,w,h must not be equal to any of other x,y,w,h

 

Code::

 

class test;

  rand bit unique_bit;

  rand int unsigned num_of_reqs;

  rand bit [10:0] x[];

  rand bit [10:0] y[];

  rand bit [10:0] w[];      

  rand bit [10:0] h[];

  rand bit [10:0] frame_width;

  rand bit [10:0] frame_height;

  constraint c_num_reqs {

    num_of_reqs inside {[1:5]};

    x.size() == num_of_reqs;

    y.size() == num_of_reqs;

    w.size() == num_of_reqs;

    h.size() == num_of_reqs;

  }

 

  constraint c_frame_width {

    frame_width inside {[0:1023]}; // Constraint will fail , if you don't cap your width

    foreach (x[i]) {

      int'(x[i] + w[i])<= frame_width;

      x[i] inside {[0:frame_width]};

      w[i] inside {[0:frame_width]};

     }

  }

      

  constraint  c_frame_height {

    frame_height inside {[0:1023]}; // Constraint will fail , if you don't cap your height

    foreach (y[i]) {

      solve frame_height before x[i],h[i];

      int'(y[i] + h[i]) <= frame_height;

      y[i] inside {[0:frame_height]};

      h[i] inside {[0:frame_height]};

    }

  }

 

 constraint c_unique {

        solve unique_bit before x,y,w,h,frame_height,frame_width;

        if(unique_bit) {

          unique {x};

          unique {y};

          unique {w};

          unique {h};

        }

      }

        

  function void display();

    $display("Unique Bit:%0d",unique_bit);

    $display("Num of Requests:%0d", num_of_reqs);

    $display("Frame Height:%0d Width:%0d",frame_height,frame_width);

    foreach(x[i])

      $display("X:%04d W:%04d || Y:%04d H:%04d",x[i],w[i],y[i],h[i]);

  endfunction

        

endclass

module top;

 

  test t;

 

  initial begin

    t = new;

    if(!t.randomize()) $error("Randomization failed");

    t.display();

  end

endmodule