lib/gl_anyhash_primes.h

/* Table of primes, for use by hash tables.
   Copyright (C) 2006, 2009-2021 Free Software Foundation, Inc.
   Written by Bruno Haible <bruno@clisp.org>, 2006.

   This file is free software: you can redistribute it and/or modify
   it under the terms of the GNU Lesser General Public License as
   published by the Free Software Foundation; either version 2.1 of the
   License, or (at your option) any later version.

   This file is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public License
   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */

/* Array of primes, approximately in steps of factor 1.2.
   This table was computed by executing the Common Lisp expression
     (dotimes (i 244) (format t "nextprime(~D)~%" (ceiling (expt 1.2d0 i))))
   and feeding the result to PARI/gp.  */
static const size_t primes[] =
  {
    11, 13, 17, 19, 23, 29, 37, 41, 47, 59, 67, 83, 97, 127, 139, 167, 199,
    239, 293, 347, 419, 499, 593, 709, 853, 1021, 1229, 1471, 1777, 2129, 2543,
    3049, 3659, 4391, 5273, 6323, 7589, 9103, 10937, 13109, 15727, 18899,
    22651, 27179, 32609, 39133, 46957, 56359, 67619, 81157, 97369, 116849,
    140221, 168253, 201907, 242309, 290761, 348889, 418667, 502409, 602887,
    723467, 868151, 1041779, 1250141, 1500181, 1800191, 2160233, 2592277,
    3110741, 3732887, 4479463, 5375371, 6450413, 7740517, 9288589, 11146307,
    13375573, 16050689, 19260817, 23112977, 27735583, 33282701, 39939233,
    47927081, 57512503, 69014987, 82818011, 99381577, 119257891, 143109469,
    171731387, 206077643, 247293161, 296751781, 356102141, 427322587,
    512787097, 615344489, 738413383, 886096061, 1063315271, 1275978331,
    1531174013, 1837408799, 2204890543UL, 2645868653UL, 3175042391UL,
    3810050851UL,
#if SIZE_MAX > 4294967295UL
    4572061027UL, 5486473229UL, 6583767889UL, 7900521449UL, 9480625733UL,
    11376750877UL, 13652101063UL, 16382521261UL, 19659025513UL, 23590830631UL,
    28308996763UL, 33970796089UL, 40764955463UL, 48917946377UL, 58701535657UL,
    70441842749UL, 84530211301UL, 101436253561UL, 121723504277UL,
    146068205131UL, 175281846149UL, 210338215379UL, 252405858521UL,
    302887030151UL, 363464436191UL, 436157323417UL, 523388788231UL,
    628066545713UL, 753679854847UL, 904415825857UL, 1085298991109UL,
    1302358789181UL, 1562830547009UL, 1875396656429UL, 2250475987709UL,
    2700571185239UL, 3240685422287UL, 3888822506759UL, 4666587008147UL,
    5599904409713UL, 6719885291641UL, 8063862349969UL, 9676634819959UL,
    11611961783951UL, 13934354140769UL, 16721224968907UL, 20065469962669UL,
    24078563955191UL, 28894276746229UL, 34673132095507UL, 41607758514593UL,
    49929310217531UL, 59915172260971UL, 71898206713183UL, 86277848055823UL,
    103533417666967UL, 124240101200359UL, 149088121440451UL, 178905745728529UL,
    214686894874223UL, 257624273849081UL, 309149128618903UL, 370978954342639UL,
    445174745211143UL, 534209694253381UL, 641051633104063UL, 769261959724877UL,
    923114351670013UL, 1107737222003791UL, 1329284666404567UL,
    1595141599685509UL, 1914169919622551UL, 2297003903547091UL,
    2756404684256459UL, 3307685621107757UL, 3969222745329323UL,
    4763067294395177UL, 5715680753274209UL, 6858816903929113UL,
    8230580284714831UL, 9876696341657791UL, 11852035609989371UL,
    14222442731987227UL, 17066931278384657UL, 20480317534061597UL,
    24576381040873903UL, 29491657249048679UL, 35389988698858471UL,
    42467986438630267UL, 50961583726356109UL, 61153900471627387UL,
    73384680565952851UL, 88061616679143347UL, 105673940014972061UL,
    126808728017966413UL, 152170473621559703UL, 182604568345871671UL,
    219125482015045997UL, 262950578418055169UL, 315540694101666193UL,
    378648832921999397UL, 454378599506399233UL, 545254319407679131UL,
    654305183289214771UL, 785166219947057701UL, 942199463936469157UL,
    1130639356723763129UL, 1356767228068515623UL, 1628120673682218619UL,
    1953744808418662409UL, 2344493770102394881UL, 2813392524122873857UL,
    3376071028947448339UL, 4051285234736937517UL, 4861542281684325481UL,
    5833850738021191727UL, 7000620885625427969UL, 8400745062750513217UL,
    10080894075300616261UL, 12097072890360739951UL, 14516487468432885797UL,
    17419784962119465179UL,
#endif
    SIZE_MAX /* sentinel, to ensure the search terminates */
  };

/* Returns a suitable prime >= ESTIMATE.  */
static size_t
next_prime (size_t estimate)
{
  size_t i;

  for (i = 0; i < sizeof (primes) / sizeof (primes[0]); i++)
    if (primes[i] >= estimate)
      return primes[i];
  return SIZE_MAX; /* not a prime, but better than nothing */
}