Failed to randomize dynamic array using foreach in constraint

Question

In the following code, I force a random variable 'ResBlks' with a value (setting its rand_mode to 0), then attempt to randomize the transaction:

`include "uvm_macros.svh"
package mytest;
import uvm_pkg::*;
typedef enum logic {Type2=0, Sorted=1} PhyRBAlloc_t; // RBs allocation type
class Txn extends uvm_sequence_item;
 rand bit [6:0] ResBlks; // Number of resource blocks (NRB)
 rand PhyRBAlloc_t PhyRBAllocType; // Physical RB allocation type
 rand integer PhyRB[2][]; // Physical RB mapping
 // Array of unique values
 constraint ArrSize {
 PhyRB[0].size() > 0;
 PhyRB[0].size() <= ResBlks;
 PhyRB[1].size() == PhyRB[0].size();
 }
 constraint vals {
 foreach(PhyRB[0][i]) PhyRB[0][i] < ResBlks;
 if(PhyRBAllocType == Type2) {
 foreach(PhyRB[1][i]) PhyRB[1][i] < ResBlks;
 }
 unique { PhyRB[0] };
 unique { PhyRB[1] } ;
 }
 constraint ResBlksConstraint {
 ResBlks inside {6,15,25,50,75,100};
 }
 function void post_randomize;
 if(PhyRBAllocType == Sorted) begin
 PhyRB[0].sort();
 PhyRB[1] = PhyRB[0];
 end
 endfunction
 function new(string name="Txn");
 super.new(name);
 endfunction
 `uvm_object_utils_begin(Txn)
 `uvm_field_int(ResBlks, UVM_DEFAULT)
 `uvm_field_array_int(PhyRB[0], UVM_DEFAULT)
 `uvm_field_array_int(PhyRB[1], UVM_DEFAULT)
 `uvm_object_utils_end
endclass
class Seq extends uvm_sequence #(Txn);
 `uvm_object_utils(Seq)
 function new(string name="Seq");
 super.new(name);
 endfunction
 task body();
 req = Txn::type_id::create("req");
 start_item(req);
 req.ResBlks = 50;
 req.ResBlks.rand_mode(0);
 if(!req.randomize())
 `uvm_error("RAND", "txn rand failed")
 finish_item(req);
 endtask: body
endclass: Seq
typedef uvm_sequencer #(Txn) Sqr;
class Drv extends uvm_driver#(Txn);
 `uvm_component_utils(Drv)
 virtual MyIf vif;
 Txn txn;
 function new(string name="Drv", uvm_component parent=null);
 super.new(name, parent);
 endfunction
 function void build_phase(uvm_phase phase);
 if(!uvm_config_db #(virtual MyIf)::get(this, "", "vif", vif))
 `uvm_fatal("NO VIF", "No virtual interface");
 endfunction: build_phase
 task run_phase(uvm_phase phase);
 vif.nRst = 0;
 vif.Init = 0;
 #100 @(negedge vif.Clk);
 vif.nRst = 1;
 forever begin
 seq_item_port.get_next_item(txn);
 // drive txn
 @vif.cb
 vif.cb.ResBlks <= txn.ResBlks;
 vif.cb.Init <= 1;
 @vif.cb vif.cb.Init <= 0;
 @vif.cb GenRBAlloc;
 seq_item_port.item_done();
 end
 endtask: run_phase
 task GenRBAlloc;
 integer i;
 if(!txn.randomize(PhyRBAllocType))
 `uvm_error("RAND", "PhyRBAllocType rand failed")
 if(!txn.randomize(PhyRB))
 `uvm_error("RAND", "PhyRB rand failed")
 `uvm_info("SFRM", $sformatf("UsedRBNum: %0d", txn.PhyRB[0].size()), UVM_MEDIUM)
 `uvm_info("SFRM", $sformatf("RB allocation: %s", txn.PhyRBAllocType.name()), UVM_MEDIUM)
 `uvm_info("SFRM", $sformatf("PhyRB[0]: %0p", txn.PhyRB[0]), UVM_MEDIUM)
 `uvm_info("SFRM", $sformatf("PhyRB[1]: %0p", txn.PhyRB[1]), UVM_MEDIUM)
 endtask: GenRBAlloc
endclass: Drv
class Agent extends uvm_agent;
 `uvm_component_utils(Agent)
 Sqr sqr;
 Drv drv;
 function new(string name="Agent", uvm_component parent=null);
 super.new(name, parent);
 endfunction
 function void build_phase(uvm_phase phase);
 if(get_is_active() == UVM_ACTIVE) begin
 sqr = Sqr::type_id::create("sqr", this);
 drv = Drv::type_id::create("drv", this);
 end
 endfunction: build_phase
 function void connect_phase(uvm_phase phase);
 if(get_is_active() == UVM_ACTIVE)
 drv.seq_item_port.connect(sqr.seq_item_export);
 endfunction: connect_phase
endclass: Agent
class Env extends uvm_env;
 `uvm_component_utils(Env)
 Agent agent;
 function new(string name="Env", uvm_component parent=null);
 super.new(name, parent);
 endfunction
 function void build_phase(uvm_phase phase);
 agent = Agent::type_id::create("agent", this);
 endfunction: build_phase
endclass: Env
class ParamTest extends uvm_test;
 `uvm_component_utils(ParamTest)
 Env env;
 function new(string name="ParamTest", uvm_component parent=null);
 super.new(name, parent);
 endfunction
 function void build_phase(uvm_phase phase);
 env = Env::type_id::create("env", this);
 endfunction: build_phase
 task run_phase(uvm_phase phase);
 Seq seq;
 phase.raise_objection(this);
 seq = Seq::type_id::create("seq");
 seq.start(env.agent.sqr);
 phase.drop_objection(this);
 endtask: run_phase
endclass: ParamTest
endpackage
interface MyIf (
 // Clock & reset:
 input Clk
);
parameter CQ = 0;
// Inputs
logic nRst;
logic Init; // Re-initialize the block
logic [6:0] ResBlks; // Number of resource blocks (NRB)
logic [6:0] UsedRBNum;// Length of type 2 distributed bitmap.
logic [6:0] PhyRB0;// Type 2-Distributed physical RB mapping for even slots.
logic [6:0] PhyRB1;// Type 2-Distributed physical RB mapping for odd slots.
clocking cb @(posedge Clk);
default input #1step output #CQ;
output negedge nRst;
// Inputs
output Init; // Re-initialize the block
output UsedRBNum;// Length of type 2 distributed bitmap.
output PhyRB0;// Type 2-Distributed physical RB mapping for even slots.
output PhyRB1;// Type 2-Distributed physical RB mapping for odd slots.
output ResBlks;
endclocking
endinterface
module tb;
 import mytest::*;
 import uvm_pkg::*;
 parameter CLKPRD = 8; // Clock period
 parameter CQ = 0;
 reg Clk;
MyIf uMyIf (
 // Clock & reset:
 .Clk(Clk)
);
initial begin
 Clk <= 0;
 forever #(CLKPRD/2) Clk = ~Clk;
end
initial begin
 uvm_config_db #(virtual MyIf)::set(null, "", "vif", uMyIf);
 run_test("ParamTest");
end
endmodule

Yet the randomization fails with this error:

** Failure: (vsim-7067) t2.sv(23): Index out of bounds (PhyRB[1][9]) for unpacked array of packed elements in constraint.

I tried to run QuestaSim with -solvedebug option, so it reports the following:

# Begin RandSet 1
# Random Variables:
# bit signed [31:0] PhyRB[1].size
# bit signed [31:0] PhyRB[0].size
# Constraints:
# t2.sv(16): ArrSize { (PhyRB[0].size > 0); }
# t2.sv(17): ArrSize { (PhyRB[0].size <= ResBlks); }
# t2.sv(18): ArrSize { (PhyRB[1].size == PhyRB[0].size); }
# t2.sv(12): (PhyRB[1].size >= 0);
# t2.sv(12): (PhyRB[0].size >= 0);
# * Solving RandSet 1 with ACT engine
# Solved: PhyRB[0].size = 9
# Solved: PhyRB[1].size = 9
# End RandSet 1

I don't understand, why is the foreach statement attempting to access PhyRB[1][9], although PhyRB[1].size = 9 ?!

I am running QuestaSim 10.4c simulation tool.

Answer 1

The problem is in the foreach syntax, it should be:

foreach PhyRB[,i] PhyRB[0][i] < ResBlks;