Iterate on rand variable

UVM
1

I am getting below error when I try to use rand variable in a loop.

Method setup_cfg::get_index contains a construct
not supported in constraint functions: reference to a rand variable
‘num_elements’

How to re-write this code to avoid this problem?
Thanks


class setup_cfg extends uvm_object;

  `uvm_object_utils(setup_cfg)

  rand int unsigned num_elements;
  rand bit[2:0]    id[];

function new(string name = "");
    super.new(name);
  endfunction

  function int unsigned get_index(bit[2:0] input_id);
    for(int i = 0; i < num_elements; i++) begin  <-------------- this line gives error
      if( (id[i] == input_id) ) begin
        return i;
      end
    end
  endfunction 

endclass
2

In reply to S2011:

You didn’t show us how your function was used in a constraint so we can’t show you how to rewrite it. Nevertheless, functions have to have all their input as arguments to the function and their output becomes a state variable. You might have to rewrite your function as a for each loop with implications.

3

In reply to dave_59:

Here is a simpler version of the constraint where the function is called…


class base_test extends uvm_test;
   `uvm_component_utils(base_test)


   table_cfg          t_cfg[];
   setup_cfg          s_cfg[];

   function new(string name_= "base_test", uvm_component parent = null);
      super.new(name_,parent);   
   endfunction // new

   virtual function void build_phase(uvm_phase phase);
    super.build_phase(phase);
    t_cfg         = new[6];   
    s_cfg          = new[7]; 
   endfunction // build_phase

   virtual function create_t_cfg(int num);
    int t_num;  

    t_num = num + 1;             
    if(!t_cfg[num].randomize() with {             
            t_id[2]                == s_cfg[t_num].id[s_cfg[t_num].get_index({3'b010})]; <----- call to function
          })
          begin
            `uvm_fatal(get_type_name(),"randomization failed")
          end
   endfunction

endclass