gen-sieve.c

/* Generate primesieve data.

   Contributed to the GNU project by Marco Bodrato.

Copyright 2021, 2022 Free Software Foundation, Inc.

This file is part of the GNU MP Library.

The GNU MP Library is free software; you can redistribute it and/or modify
it under the terms of either:

  * the GNU Lesser General Public License as published by the Free
    Software Foundation; either version 3 of the License, or (at your
    option) any later version.

or

  * the GNU General Public License as published by the Free Software
    Foundation; either version 2 of the License, or (at your option) any
    later version.

or both in parallel, as here.

The GNU MP Library 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 General Public License
for more details.

You should have received copies of the GNU General Public License and the
GNU Lesser General Public License along with the GNU MP Library.  If not,
see https://www.gnu.org/licenses/.  */

#include <stdio.h>
#include "bootstrap.c"

static int
bit_to_n (int bit) { return (bit*3+4)|1; }

int
generate (int limb_bits, int limit)
{
  mpz_t  limb;
  int i, lb, pc, c, totpc, maxprime;

  mpz_init (limb);

  printf ("/* This file generated by gen-sieve.c - DO NOT EDIT. */\n");
  printf ("\n");
  printf ("#if GMP_LIMB_BITS != %d\n", limb_bits);
  printf ("Error, error, this data is for %d bits\n", limb_bits);
  printf ("#endif\n");
  printf ("\n");
  printf ("#define PRIMESIEVE_INIT_TABLE ");

  maxprime = 3;
  lb = pc = c = totpc = 0;
  for (i = 0; i < limit; i++)
    {
      if (! isprime (bit_to_n (i)))
	mpz_setbit (limb, lb);
      else
	maxprime = bit_to_n (i), ++pc;
      ++lb;
      if (lb == limb_bits)
	{
	  ++c;
	  printf ("\\\n\tCNST_LIMB (0x");
	  mpz_out_str (stdout, -16, limb);
	  printf ("),\t/* %d - %d (%d primes) */\t", bit_to_n (i + 1 - limb_bits),
		  bit_to_n (i + 1) - 1, pc);
	  totpc += pc;
	  lb = pc = 0;
	  mpz_set_ui (limb, 0);
	}
    }

  if ((mpz_sgn (limb) | lb | pc) != 0)
    {
      printf ("\ngen-sieve: Internal error, during generate (%d, %d).\n", limb_bits,  limit);
      abort();
    }

  mpz_clear (limb);

  printf ("\n");
  printf ("#define PRIMESIEVE_NUMBEROF_TABLE %d\n", c);

  printf ("/* #define PRIMESIEVE_PRIMES_IN_TABLE %d */\n", totpc);
  printf ("#define PRIMESIEVE_HIGHEST_PRIME %d\n", maxprime);
  printf ("/* #define PRIMESIEVE_FIRST_UNCHECKED %d */\n", bit_to_n (limit));

  return c;
}

void
setmask (mpz_t mask, int a, int b)
{
  mpz_set_ui (mask, 0);
  for (unsigned i = 0; i < 2 * a * b; ++i)
    if ((bit_to_n (i) % a == 0) || (bit_to_n (i) % b == 0))
      mpz_setbit (mask, i);
}

void
gen_sieve_masks (int limb_bits) {
  mpz_t  mask, limb;

  mpz_init (mask);
  mpz_init (limb);

  printf ("\n");
  if (limb_bits > 60 && limb_bits < 91)
    {
      setmask (mask, 5, 11);

      mpz_tdiv_r_2exp (limb, mask, limb_bits);
      printf ("#define SIEVE_MASK1 CNST_LIMB(0x");
      mpz_out_str (stdout, -16, limb);
      printf (")\n");
      mpz_tdiv_q_2exp (limb, mask, limb_bits);
      printf ("#define SIEVE_MASKT CNST_LIMB(0x");
      mpz_out_str (stdout, -16, limb);
      printf (")\n");

      setmask (mask, 7, 13);

      mpz_tdiv_r_2exp (limb, mask, limb_bits);
      printf ("#define SIEVE_2MSK1 CNST_LIMB(0x");
      mpz_out_str (stdout, -16, limb);
      printf (")\n");
      mpz_tdiv_q_2exp (mask, mask, limb_bits);
      mpz_tdiv_r_2exp (limb, mask, limb_bits);
      printf ("#define SIEVE_2MSK2 CNST_LIMB(0x");
      mpz_out_str (stdout, -16, limb);
      printf (")\n");
      mpz_tdiv_q_2exp (limb, mask, limb_bits);
      printf ("#define SIEVE_2MSKT CNST_LIMB(0x");
      mpz_out_str (stdout, -16, limb);
      printf (")\n");
    }
  else if (limb_bits > 23 && limb_bits < 36)
    {
      setmask (mask, 5, 7);

      mpz_tdiv_r_2exp (limb, mask, limb_bits);
      printf ("#define SIEVE_MASK1 CNST_LIMB(0x");
      mpz_out_str (stdout, -16, limb);
      printf (")\n");
      mpz_tdiv_q_2exp (mask, mask, limb_bits);
      mpz_tdiv_r_2exp (limb, mask, limb_bits);
      printf ("#define SIEVE_MASK2 CNST_LIMB(0x");
      mpz_out_str (stdout, -16, limb);
      printf (")\n");
      mpz_tdiv_q_2exp (limb, mask, limb_bits);
      printf ("#define SIEVE_MASKT CNST_LIMB(0x");
      mpz_out_str (stdout, -16, limb);
      printf (")\n");
    }
  printf ("\n");

  mpz_clear (limb);
  mpz_clear (mask);
}

/* 5*2 = 10
   7*2 = 14
   5*7*2 = 70 (2*35, 3*24, 4*18, 5*14...)
   5*11*2 = 110 (2*55, 3*37, 4*28, 5*22...)
   5*13*2 = 130 (2*65, 3*44, 4*33, 5*26...)
   7*11*2 = 154 (2*77, 3*52, 4*39, 5*31...)
   7*13*2 = 182 (2*91, 3*61, 4*46, 5*37...)
*/

int
main (int argc, char *argv[])
{
  int  limb_bits, limit;

  if (argc != 2)
    {
      fprintf (stderr, "Usage: gen-sieve <limbbits>\n");
      exit (1);
    }

  limb_bits = atoi (argv[1]);

  limit = 64 * 28; /* bits in the presieved sieve */
  if (limit % limb_bits != 0)
    limit += limb_bits - limit % limb_bits;
  generate (limb_bits, limit);
  gen_sieve_masks (limb_bits);

  return 0;
}