library math;

package body random is

  use math.math_real;


    constant sample_seeds : seed_array(0 to 50)
                 := (  0 => (1, 1),
                       1 => (1919456777, 2006618587),
                       2 => (928906921, 476680813),
                       3 => (715788085, 762347824),
                       4 => (366002668, 1804336679),
                       5 => (1866585254, 247488051),
                       6 => (1342990589, 1539624735),
                       7 => (677313287, 1675609237),
                       8 => (644816519, 2026475269),
                       9 => (1654953611, 564421524),
                      10 => (1020104619, 712556314),
                      11 => (609798541, 1592526288),
                      12 => (1106087470, 1468242308),
                      13 => (1378844312, 646793513),
                      14 => (966261604, 481733031),
                      15 => (1407842093, 1316990206),
                      16 => (1705378215, 1930221363),
                      17 => (206887499, 1810320799),
                      18 => (1681633030, 2114795480),
                      19 => (71194926, 1642522201),
                      20 => (663275331, 1947299255),
                      21 => (224432387, 944962866),
                      22 => (1156075861, 1866435087),
                      23 => (1670357576, 1247152991),
                      24 => (846934138, 1673364736),
                      25 => (1972636955, 1404522710),
                      26 => (533484185, 592078395),
                      27 => (1989468008, 1409246301),
                      28 => (697086615, 1975145057),
                      29 => (111393259, 1673620688),
                      30 => (1352201163, 872947497),
                      31 => (1342844190, 877696585),
                      32 => (938770066, 1222894811),
                      33 => (1144599578, 661919919),
                      34 => (1750521407, 269946538),
                      35 => (457892500, 1256953520),
                      36 => (1678589945, 356027520),
                      37 => (1484458924, 2103068828),
                      38 => (1296978761, 2124096638),
                      39 => (1702642440, 1161000593),
                      40 => (1244690090, 2016422304),
                      41 => (1858682943, 1053836731),
                      42 => (1496964676, 701079294),
                      43 => (432696952, 602526767),
                      44 => (2097684438, 1264032473),
                      45 => (2115456834, 298917738),
                      46 => (432301768, 232430346),
                      47 => (1929812456, 758157910),
                      48 => (1655564027, 1062345086),
                      49 => (1116121051, 538424126),
                      50 => (844396720, 821616997) );


  procedure init_fixed ( random_info : out random_info_record;
                         mean : in real ) is
  begin
    random_info.distribution := fixed;
    random_info.mean := mean;
  end procedure init_fixed;


  procedure init_uniform ( random_info : out random_info_record;
                           lower_bound, upper_bound : in real;
                           seed : in seed_type ) is
  begin
    assert lower_bound <= upper_bound
      report "init_uniform: lower_bound > upper_bound" severity failure;
    random_info.distribution := uniform;
    random_info.lower_bound := lower_bound;
    random_info.upper_bound := upper_bound;
    random_info.seed := seed;
  end procedure init_uniform;


  procedure init_exponential ( random_info : out random_info_record;
                               mean : in real;
                               seed : in seed_type ) is
  begin
    assert mean > 0.0
      report "init_exponential: mean not positive" severity failure;
    random_info.distribution := exponential;
    random_info.mean := mean;
    random_info.seed := seed;
  end procedure init_exponential;


  procedure generate_uniform ( random_info : inout random_info_record;
                               random_number : out real ) is
    variable tmp : real;
  begin
    math_real.uniform(random_info.seed.seed1, random_info.seed.seed2, tmp);
    random_number := random_info.lower_bound
                     + tmp * (random_info.upper_bound - random_info.lower_bound);
  end procedure generate_uniform;


  procedure generate_exponential ( random_info : inout random_info_record;
                                   random_number : out real ) is
    variable tmp : real;
  begin
    loop
      math_real.uniform(random_info.seed.seed1, random_info.seed.seed2, tmp);
      exit when tmp /= 0.0;
    end loop;
    random_number := - random_info.mean * math_real.log(tmp);
  end procedure generate_exponential;


  procedure generate_random ( random_info : inout random_info_record;
                              random_number : out real ) is
  begin
    case random_info.distribution is
      when fixed =>
        random_number := random_info.mean;
      when uniform =>
        generate_uniform(random_info, random_number);
      when exponential =>
        generate_exponential(random_info, random_number);
    end case;
  end procedure generate_random;


end package body random;