verilator/test_regress/t/t_process_rand.v

// DESCRIPTION: Verilator: Verilog Test module
//
// This file ONLY is placed under the Creative Commons Public Domain.
// SPDX-FileCopyrightText: 2023 Antmicro Ltd
// SPDX-License-Identifier: CC0-1.0

module t;
  process p;

  integer seed;
  string state;
  int a;
  int b;

  initial begin
    p = process::self();

    // Test setting RNG state with state string
    state = p.get_randstate();
    p.set_randstate(state);
    a = $random;
    p.set_randstate(state);
    b = $random;
    $display("a=%d, b=%d", a, b);
    if (a != b) $stop;

    // Test the same with $urandom
    state = p.get_randstate();
    p.set_randstate(state);
    a = $urandom;
    p.set_randstate(state);
    b = $urandom;
    $display("a=%d, b=%d", a, b);
    if (a != b) $stop;

    // Test if the results repeat after the state is reset
    state = p.get_randstate();
    for (int i = 0; i < 10; i++) $random;
    a = $random;
    // Now reset the state and take 11th result again
    p.set_randstate(state);
    for (int i = 0; i < 10; i++) $random;
    b = $random;
    $display("a=%d, b=%d", a, b);
    if (a != b) $stop;

    $write("*-* All Finished *-*\n");
    $finish;
  end
endmodule