same value for a RANDC variable of base class in extended class objects

i have a randc variable "index" in c_base . i've two new classes ( class_1 & class_2 ) extended from base_class. when randomizing the extended class objects, i observed the variable "index" is having same values in C1 & C2 objects. Below is the simplified copy of my code: class c_base extends uvm_sequence_item; rand bit [9:0] index; `uvm_object_utils_begin(c_base) `uvm_field_int(index,UVM_ALL_ON) `uvm_object_utils_end function new(string name="c_base"); super.new(name); endfunction endclass class class_1 extends c_base; rand bit [3:0] var1; rand bit [7:0] var2; rand bit [3:0] var3; `uvm_object_utils_begin(class_1) `uvm_field_int(var1,UVM_ALL_ON) `uvm_field_int(var2,UVM_ALL_ON) `uvm_field_int(var3,UVM_ALL_ON) `uvm_object_utils_end function new(string name="class_1"); super.new(name); endfunction endclass class class_2 extends c_base; rand bit [4:0] var4; rand bit [10:0] var5; `uvm_object_utils_begin(class_2) `uvm_field_int(var4,UVM_ALL_ON) `uvm_field_int(var5,UVM_ALL_ON) `uvm_object_utils_end function new(string name="class_2"); super.new(name); endfunction endclass module tst; class_1 c1[]; class_2 c2[]; c_base q[$]; initial begin c1=new[20]; c2=new[20]; foreach(c1[i]) begin c1[i]=class_1::type_id::create($sformatf("c1_%0d",i)); assert( c1[i].randomize() ); q.push_back(c1[i]); end foreach(c2[i]) begin c2[i]=class_2::type_id::create($sformatf("c2_%0d",i)); assert( c2[i].randomize() ); q.push_back(c2[i]); end q.sort with(item.index); $display("---------------"); $display(" Index Name "); $display("---------------"); for(int i=0; i<q.size();i++) begin $display(" x%h %s",q[i].index,q[i].get_name()); end end endmodule EdaPlayground link: https://www.edaplayground.com/x/3pk2 For the above code in EdaPlayground, I'm creating 20 objects for both classes and got same index value ( x398, x2d7) for a class_1 & class_2 objects. What I expected was, the index value of all objects will be unique until all combinations are exercised. My intention is to use "index" as the location of SRAM address to store the packed data of each extended class object. Is this the expected behavior in SimVision15.20?? Can't i get unique values for variable index ?Image may be NSFW.
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