Associative array of covergroups

SystemVerilog
,
1

Hello,

Is it possible to have an associative array of covergroups? I am not sure whether it is the right way to phrase this question but posting my requirement below

  1. I intend to cover the clock ratios between different clocks in a design.
  2. The clock ratios between different clocks is available as an associative array (int clock_ratios[string]). The string index would be something like “clk1_x_clk2”.
  3. The clock ratios is an associative array because the number of clocks may vary depending on the design configuration.

What i intend to have

covergroup clk_ratios_cg with function sample(int clk_ratio);
  RATIO: coverpoint clk_ratio {
    bins low = {[1 : 5]};
    bins med = {[6 : 19]};
    bins high = {[20 : $]};
  }
endgroup

class my_class extends my_base_class;
  `uvm_component_utils(my_class)

  int clk_ratios[string];
  clk_ratios_cg ratio_cg[string]; // Can we do this?

  virtual task monitor_clk_period(); // called in run_phase
    foreach(config_item[i]) begin // config item from config db from the test top. The test top has some logic to figure out the number of clocks
      automatic string clk_name = i;
      fork begin
        forever begin
          calculate_clk_ratios(clk_name);
          @clk[name].half_clk_period; //clk is an associaive array from my base class having some clock attributes
        end
      end
      join_none
    end
  endtask

  virtual function calculate_clk_ratios(string clk_name);
    foreach(config_item[i]) begin
      if(i == clk_name) continue; // No need of clk_ratio of clock to itself!!
      else begin
        clk_ratios[$sformatf("%s_x_%s", name, i)] = (clk[name].half_clk_period/clk[i].half_clk_period);
        // Can we use sample function of clk_ratios_cg for each ratio_cg[$sformatf("%s_x_%s", name, i]
        // But then do we need to new ratio_cg. new() cannot be done here 
      end
    end
  endfunction  

endclass

From the above snippet, i want to cover the clk_ratio values in associative array clk_ratios[$sformatf(“%s_x_%s”, name, i] for the bins mentioned in clk_ratios_cg

2

Hi Dave,

Thanks for your reply.
I tried your suggestion, but i am getting the below error

ratio_cg[ratio_name] = new(); // only construct once on first reference
** Error: (vlog-13069) near “ratio_cg”: syntax error, unexpected IDENTIFIER.

We are using QuestaSim 2021.4.
Does this version of questa support newing of the cover group outside of the class constructor?

3

For the time being, we were able to work around this issue by moving the new() of the cover groups to build phase.

// Build Phase
  virtual function void build_phase (uvm_phase phase);
   super.build_phase(phase);
   foreach(config_item[j]) begin
     foreach(config_item[i]) begin
       if(i == j) continue;
       else begin
         string ratio_name = $sformatf("%s_x_%s", j, i);
         ratio_cg[ratio_name] = new;
       end
     end
   end
  endfunction