Constraint to print pattern 122333444455555

SystemVerilog
, ,
1

How to write constraint to print
1 22 333 4444 55555?
I tried to use foreach loop but can’t get the output.

1 Like
2 
class cons_pattern;   
  rand int arr[5];
  
  constraint c1 {foreach(arr[i])
    arr[i]==pattern(i);	 			
  } 
    function int pattern(int i);
      static int num=1;
      int res;
              res=(i+1) *num;
              num=num+10**(i+1);
			return res;        
    endfunction    
endclass
3

It prints this output.
array : '{1, 22, 93, 244, 505}

4

//1 22 333 4444 55555

class trans;
  parameter num=5;
  bit [3:0] q[$];
  rand bit [3:0] k[num];

  function bit [3:0] varr1 (integer j);
    for(int i=0;i<j;i++) 
      q.push_back(j);
    varr1 = j;
  endfunction
  
  constraint cond{ 
    foreach(k[i]){      
      k[i] == varr1(i+1);
    } 
  }
      
  function void post_randomize();
    $display("array : %0p",q);
  endfunction : post_randomize
  
endclass : trans

trans tr;

module tb;
  initial begin
    tr = new();
    tr.randomize();
  end
endmodule : tb

i tried above code and it works using cadence and questa tool. Is there any other way to write its constraint and without writing any logic in post randomize function?

5

inside function change these 2 lines, it will work
res=(i+1) * num;
num=num+10**(i+1);

6

Calling a function in a constraint with side-effects is unpredictable because you can’t control how many times the function gets called in the evaluation of a constraint.

9 
class first;
rand int ar[][];
  int a[$];
 function new();
	$display("Inside first");
 endfunction

constraint ct{
  ar.size()==6;
foreach(ar[i]){
  ar[i].size()==i+1;
}
  foreach(ar[i,j])
  {
    ar[i][j] == i+1;
  }
}

  function void post_randomize();
  foreach(ar[i,j])
    begin
      a.push_back(ar[i][j]);
    end
  endfunction
function dis();
  $display("ar=%p",a);
endfunction
endclass


module top;
initial begin
first f=new();
f.randomize();
f.dis();
end
endmodule

//output
Inside first
value ar='{1, 2, 2, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6}

1 Like
10

Thank you

11 
class pattern;
	rand int a[];
	constraint c2 { a.size==6;}
	constraint c1 { foreach (a[i])
			a[i]==(1*(i+1)*(10**(i+1)-1))/9;}

endclass
module m;
pattern p;
initial
begin
	p=new;
	assert(p.randomize);
	foreach(p.a[i])
	$display("pattern is %d",p.a[i]);
		end
endmodule
12

thought this is simpler

class my_class;
  rand bit[3:0] my_q[$];
  rand bit[3:0] temp_val;

  constraint c1{
    temp_val inside {[1:9]};
  }

  function void pre_randomize();
    my_q.delete();
  endfunction

  function void post_randomize();
    for(int i=temp_val;i>0;i=i-1) begin
      repeat(i) begin
        my_q.push_front(i);
      end
    end
  endfunction
endclass

module top;
  my_class m1;

  initial begin
    m1=new();
    repeat(5) begin
      m1.randomize();
      $display("Value of temp_val=%0d",m1.temp_val);
      foreach(m1.my_q[i]) begin
        $write("%0d",m1.my_q[i]);
      end
      $display("\n=========");
    end
  end
endmodule
13 
// Code your testbench here
// or browse Examples

class test;
  
  // pattern: 1223334444
  rand int unsigned value;
  
  int unsigned count;
  int unsigned curr_num = 1;
  int unsigned val_q[$];
  
  constraint cons{
    if(curr_num == 1) {
      value == 1;      
    }
      else if(count < curr_num) {
        value == curr_num;
      }       
  }
  
  function void post_randomize();
    count++;
    if(count == curr_num) begin
      curr_num++;
      count=0;
    end
    val_q.push_back(value);
    
  endfunction : post_randomize
endclass : test

module tb;
  
  initial begin
    test t = new();
    
    repeat(50) begin
      assert(t.randomize());  
    end
    
    $display(" %0p", t.val_q);
  end
  
endmodule : tb