Constraint to have N elements distributed in M bins

Code to distribute N elements into M bins, you add unique keyword to have each bin will have unique number of elements.

class test;
  parameter int M = 5;
  parameter int N = 100;
  rand bit[31:0] arr[M];
  
  constraint c_arr { arr.sum() == N; foreach(arr[i]) { arr[i] inside {[0:N-1]}; } unique {arr}; }
  
  function void post_randomize();
    foreach(arr[i])
    $display("Array[%01d]:%02d\n",i,arr[i]);
  endfunction
  
endclass

module top;
  test t;
  
  initial begin
    t = new;
    void'(t.randomize());
  end
endmodule

RESULT:

Compiler version U-2023.03-SP2_Full64; Runtime version U-2023.03-SP2_Full64; Sep 17 10:38 2024
Array[0]:23

Array[1]:01

Array[2]:10

Array[3]:11

Array[4]:15

Array[5]:21

Array[6]:14

Array[7]:03

Array[8]:02

Array[9]:00

V C S S i m u l a t i o n R e p o r t
Time: 0 ns
CPU Time: 0.430 seconds; Data structure size: 0.0Mb
Tue Sep 17 10:38:13 2024

CIRCULAR QUEUE implementation in System Verilog

NOTE:

Print Statements are implemented on every function call.

The Read pointer in dequeue is incremented by one, if not empty before the print.

Same is the case for write pointer.

In this setup, I used the MSB of wr_ptr and rd_ptr to represent a rollover of the memory ( array ).This in turn is used to generate the FULL and EMPTY signals.

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class circular_queue; parameter int N = 5; parameter int WIDTH = 3; int arr[N]; bit isFull; bit isEmpty; bit [WIDTH:0] wr_ptr; //clog2 ?? bit [WIDTH:0] rd_ptr; extern function new(); extern function void enqueue(int val); extern function int dequeue(); extern function int peek(); endclass: circular_queue function circular_queue::new(); isEmpty = 1; isFull = 0; endfunction: new function void circular_queue::enqueue(int val); if(!isFull) begin isEmpty = 0; arr[wr_ptr[WIDTH-1:0]] = val; wr_ptr[WIDTH-1:0] = (wr_ptr[WIDTH-1:0]+1) % N; wr_ptr[WIDTH] = wr_ptr[WIDTH-1:0] == 0 ? ~wr_ptr[WIDTH] : wr_ptr[WIDTH]; end isFull = ( wr_ptr[WIDTH-1:0] == rd_ptr[WIDTH-1:0] && wr_ptr[WIDTH]!=rd_ptr[WIDTH]) ? 1 : 0; $display("ENQUEUE:: WR_PTR:%d RD_PTR:%d VAL:%02d ARR:%p FULL:%d EMPTY:%d",wr_ptr[WIDTH-1:0],rd_ptr[WIDTH-1:0],val,arr,isFull,isEmpty); endfunction: enqueue function int circular_queue::dequeue(); int val; if(!isEmpty) begin isFull = 0; val = arr[rd_ptr[WIDTH-1:0]]; rd_ptr[WIDTH-1:0] = (rd_ptr[WIDTH-1:0]+1) % N; rd_ptr[WIDTH] = rd_ptr[WIDTH-1:0] == 0 ? ~rd_ptr[WIDTH] : rd_ptr[WIDTH]; end isEmpty = ( wr_ptr[WIDTH-1:0] == rd_ptr[WIDTH-1:0] && wr_ptr[WIDTH]==rd_ptr[WIDTH]) ? 1 : 0; $display("DEQUEUE:: WR_PTR:%d RD_PTR:%d VAL:%02d ARR:%p FULL:%d EMPTY:%d",wr_ptr[WIDTH-1:0],rd_ptr[WIDTH-1:0],val,arr,isFull,isEmpty); return val; endfunction: dequeue function int circular_queue::peek(); int val; if(!isEmpty) val = arr[rd_ptr]; $display("PEEK :: WR_PTR:%d RD_PTR:%d VAL:%02d ARR:%p FULL:%d EMPTY:%d",wr_ptr[WIDTH-1:0],rd_ptr[WIDTH-1:0],val,arr,isFull,isEmpty); return val; endfunction: peek module top; circular_queue cq; initial begin int wr_val; int rd_val; cq = new; repeat(4) begin wr_val = $urandom_range(1,100); cq.enqueue(wr_val); end repeat(20) begin randcase 2 : begin wr_val = $urandom_range(1,100); cq.enqueue(wr_val); end 2 : begin rd_val = cq.dequeue(); end 1 : begin rd_val = cq.peek(); end endcase end end endmodule: top

> OUTPUT::

Chronologic VCS simulator copyright 1991-2021
Contains Synopsys proprietary information.
Compiler version S-2021.09; Runtime version S-2021.09; Apr 22 02:40 2023
ENQUEUE:: WR_PTR:1 RD_PTR:0 VAL:39 ARR:'{39, 0, 0, 0, 0} FULL:0 EMPTY:0
ENQUEUE:: WR_PTR:2 RD_PTR:0 VAL:61 ARR:'{39, 61, 0, 0, 0} FULL:0 EMPTY:0
ENQUEUE:: WR_PTR:3 RD_PTR:0 VAL:74 ARR:'{39, 61, 74, 0, 0} FULL:0 EMPTY:0
ENQUEUE:: WR_PTR:4 RD_PTR:0 VAL:71 ARR:'{39, 61, 74, 71, 0} FULL:0 EMPTY:0
DEQUEUE:: WR_PTR:4 RD_PTR:1 VAL:39 ARR:'{39, 61, 74, 71, 0} FULL:0 EMPTY:0
ENQUEUE:: WR_PTR:0 RD_PTR:1 VAL:97 ARR:'{39, 61, 74, 71, 97} FULL:0 EMPTY:0
ENQUEUE:: WR_PTR:1 RD_PTR:1 VAL:23 ARR:'{23, 61, 74, 71, 97} FULL:1 EMPTY:0
PEEK :: WR_PTR:1 RD_PTR:1 VAL:61 ARR:'{23, 61, 74, 71, 97} FULL:1 EMPTY:0
ENQUEUE:: WR_PTR:1 RD_PTR:1 VAL:91 ARR:'{23, 61, 74, 71, 97} FULL:1 EMPTY:0
DEQUEUE:: WR_PTR:1 RD_PTR:2 VAL:61 ARR:'{23, 61, 74, 71, 97} FULL:0 EMPTY:0
ENQUEUE:: WR_PTR:2 RD_PTR:2 VAL:58 ARR:'{23, 58, 74, 71, 97} FULL:1 EMPTY:0
DEQUEUE:: WR_PTR:2 RD_PTR:3 VAL:74 ARR:'{23, 58, 74, 71, 97} FULL:0 EMPTY:0
DEQUEUE:: WR_PTR:2 RD_PTR:4 VAL:71 ARR:'{23, 58, 74, 71, 97} FULL:0 EMPTY:0
PEEK :: WR_PTR:2 RD_PTR:4 VAL:97 ARR:'{23, 58, 74, 71, 97} FULL:0 EMPTY:0
ENQUEUE:: WR_PTR:3 RD_PTR:4 VAL:27 ARR:'{23, 58, 27, 71, 97} FULL:0 EMPTY:0
DEQUEUE:: WR_PTR:3 RD_PTR:0 VAL:97 ARR:'{23, 58, 27, 71, 97} FULL:0 EMPTY:0
DEQUEUE:: WR_PTR:3 RD_PTR:1 VAL:23 ARR:'{23, 58, 27, 71, 97} FULL:0 EMPTY:0
DEQUEUE:: WR_PTR:3 RD_PTR:2 VAL:58 ARR:'{23, 58, 27, 71, 97} FULL:0 EMPTY:0
ENQUEUE:: WR_PTR:4 RD_PTR:2 VAL:20 ARR:'{23, 58, 27, 20, 97} FULL:0 EMPTY:0
DEQUEUE:: WR_PTR:4 RD_PTR:3 VAL:27 ARR:'{23, 58, 27, 20, 97} FULL:0 EMPTY:0
DEQUEUE:: WR_PTR:4 RD_PTR:4 VAL:20 ARR:'{23, 58, 27, 20, 97} FULL:0 EMPTY:1
DEQUEUE:: WR_PTR:4 RD_PTR:4 VAL:00 ARR:'{23, 58, 27, 20, 97} FULL:0 EMPTY:1
ENQUEUE:: WR_PTR:0 RD_PTR:4 VAL:06 ARR:'{23, 58, 27, 20, 6} FULL:0 EMPTY:0
ENQUEUE:: WR_PTR:1 RD_PTR:4 VAL:73 ARR:'{73, 58, 27, 20, 6} FULL:0 EMPTY:0
V C S S i m u l a t i o n R e p o r t
Time: 0 ns
CPU Time: 0.700 seconds; Data structure size: 0.0Mb
Sat Apr 22 02:40:54 2023