gen-bases.c

/* Generate mp_bases data.

Copyright 1991, 1993, 1994, 1996, 2000, 2002, 2004 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 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.

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 Lesser General Public
License for more details.

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

#include <math.h>

#include "dumbmp.c"


int    chars_per_limb;
double chars_per_bit_exactly;
mpz_t  big_base;
int    normalization_steps;
mpz_t  big_base_inverted;

mpz_t  t;

#define POW2_P(n)  (((n) & ((n) - 1)) == 0)

unsigned int
ulog2 (unsigned int x)
{
  unsigned int i;
  for (i = 0;  x != 0;  i++)
    x >>= 1;
  return i;
}

void
generate (int limb_bits, int nail_bits, int base)
{
  int  numb_bits = limb_bits - nail_bits;

  mpz_set_ui (t, 1L);
  mpz_mul_2exp (t, t, numb_bits);
  mpz_set_ui (big_base, 1L);
  chars_per_limb = 0;
  for (;;)
    {
      mpz_mul_ui (big_base, big_base, (long) base);
      if (mpz_cmp (big_base, t) > 0)
        break;
      chars_per_limb++;
    }

  chars_per_bit_exactly = 0.69314718055994530942 / log ((double) base);

  mpz_ui_pow_ui (big_base, (long) base, (long) chars_per_limb);

  normalization_steps = limb_bits - mpz_sizeinbase (big_base, 2);

  mpz_set_ui (t, 1L);
  mpz_mul_2exp (t, t, 2*limb_bits - normalization_steps);
  mpz_tdiv_q (big_base_inverted, t, big_base);
  mpz_set_ui (t, 1L);
  mpz_mul_2exp (t, t, limb_bits);
  mpz_sub (big_base_inverted, big_base_inverted, t);
}

void
header (int limb_bits, int nail_bits)
{
  int  numb_bits = limb_bits - nail_bits;

  generate (limb_bits, nail_bits, 10);

  printf ("/* This file generated by gen-bases.c - DO NOT EDIT. */\n");
  printf ("\n");
  printf ("#if GMP_NUMB_BITS != %d\n", numb_bits);
  printf ("Error, error, this data is for %d bits\n", numb_bits);
  printf ("#endif\n");
  printf ("\n");
  printf ("/* mp_bases[10] data, as literal values */\n");
  printf ("#define MP_BASES_CHARS_PER_LIMB_10      %d\n", chars_per_limb);
  printf ("#define MP_BASES_BIG_BASE_10            CNST_LIMB(0x");
  mpz_out_str (stdout, 16, big_base);
  printf (")\n");
  printf ("#define MP_BASES_BIG_BASE_INVERTED_10   CNST_LIMB(0x");
  mpz_out_str (stdout, 16, big_base_inverted);
  printf (")\n");
  printf ("#define MP_BASES_NORMALIZATION_STEPS_10 %d\n", normalization_steps);
}

void
table (int limb_bits, int nail_bits)
{
  int  numb_bits = limb_bits - nail_bits;
  int  base;

  printf ("/* This file generated by gen-bases.c - DO NOT EDIT. */\n");
  printf ("\n");
  printf ("#include \"gmp.h\"\n");
  printf ("#include \"gmp-impl.h\"\n");
  printf ("\n");
  printf ("#if GMP_NUMB_BITS != %d\n", numb_bits);
  printf ("Error, error, this data is for %d bits\n", numb_bits);
  printf ("#endif\n");
  printf ("\n");
  puts ("const struct bases mp_bases[257] =\n{");
  puts ("  /*   0 */ { 0, 0.0, 0 },");
  puts ("  /*   1 */ { 0, 1e37, 0 },");
  for (base = 2; base <= 256; base++)
    {
      generate (limb_bits, nail_bits, base);

      printf ("  /* %3u */ { ", base);
      if (POW2_P (base))
	{
          printf ("%u, %.16f, 0x%x },\n",
                  chars_per_limb, chars_per_bit_exactly, ulog2 (base) - 1);
	}
      else
	{
          printf ("%u, %.16f, CNST_LIMB(0x",
                  chars_per_limb, chars_per_bit_exactly);
	  mpz_out_str (stdout, 16, big_base);
          printf ("), CNST_LIMB(0x");
	  mpz_out_str (stdout, 16, big_base_inverted);
          printf (") },\n");
	}
    }

  puts ("};");
}

int
main (int argc, char **argv)
{
  int  limb_bits, nail_bits;

  mpz_init (big_base);
  mpz_init (big_base_inverted);
  mpz_init (t);

  if (argc != 4)
    {
      fprintf (stderr, "Usage: gen-bases <header|table> <limbbits> <nailbits>\n");
      exit (1);
    }

  limb_bits = atoi (argv[2]);
  nail_bits = atoi (argv[3]);

  if (limb_bits <= 0
      || nail_bits < 0
      || nail_bits >= limb_bits)
    {
      fprintf (stderr, "Invalid limb/nail bits: %d %d\n",
               limb_bits, nail_bits);
      exit (1);
    }

  if (strcmp (argv[1], "header") == 0)
    header (limb_bits, nail_bits);
  else if (strcmp (argv[1], "table") == 0)
    table (limb_bits, nail_bits);
  else
    {
      fprintf (stderr, "Invalid header/table choice: %s\n", argv[1]);
      exit (1);
    }

  return 0;
}