/* Test for sqrmod_bnm1 function.

   Contributed to the GNU project by Marco Bodrato.

Copyright 2009 Free Software Foundation, Inc.

This file is part of the GNU MP Library test suite.

The GNU MP Library test suite is free software; you can redistribute it

and/or modify it under the terms of the GNU 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 test suite 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 a copy of the GNU General Public License along with

the GNU MP Library test suite.  If not, see https://www.gnu.org/licenses/.  */

#include <stdlib.h>

#include <stdio.h>

#include "gmp.h"

#include "gmp-impl.h"

#include "tests.h"

/* Sizes are up to 2^SIZE_LOG limbs */

#ifndef SIZE_LOG

#define SIZE_LOG 12

#endif

#ifndef COUNT

#define COUNT 3000

#endif

#define MAX_N (1L << SIZE_LOG)

#define MIN_N 1

/*

  Reference function for squaring modulo B^rn-1.

  The result is expected to be ZERO if and only if one of the operand

  already is. Otherwise the class [0] Mod(B^rn-1) is represented by

  B^rn-1. This should not be a problem if sqrmod_bnm1 is used to

  combine results and obtain a natural number when one knows in

  advance that the final value is less than (B^rn-1).

*/

static void

ref_sqrmod_bnm1 (mp_ptr rp, mp_size_t rn, mp_srcptr ap, mp_size_t an)

{

  mp_limb_t cy;

  ASSERT (0 < an && an <= rn);

  refmpn_mul (rp, ap, an, ap, an);

  an *= 2;

  if (an > rn) {

    cy = mpn_add (rp, rp, rn, rp + rn, an - rn);

    /* If cy == 1, then the value of rp is at most B^rn - 2, so there can

     * be no overflow when adding in the carry. */

    MPN_INCR_U (rp, rn, cy);

  }

}

/*

  Compare the result of the mpn_sqrmod_bnm1 function in the library

  with the reference function above.

*/

int

main (int argc, char **argv)

{

  mp_ptr ap, refp, pp, scratch;

  int count = COUNT;

  int test;

  gmp_randstate_ptr rands;

  TMP_DECL;

  TMP_MARK;

  if (argc > 1)

    {

      char *end;

      count = strtol (argv[1], &end, 0);

      if (*end || count <= 0)

	{

	  fprintf (stderr, "Invalid test count: %s.\n", argv[1]);

	  return 1;

	}

    }

  tests_start ();

  rands = RANDS;

  ASSERT_ALWAYS (mpn_sqrmod_bnm1_next_size (MAX_N) == MAX_N);

  ap = TMP_ALLOC_LIMBS (MAX_N);

  refp = TMP_ALLOC_LIMBS (MAX_N * 4);

  pp = 1+TMP_ALLOC_LIMBS (MAX_N + 2);

  scratch

    = 1+TMP_ALLOC_LIMBS (mpn_sqrmod_bnm1_itch (MAX_N, MAX_N) + 2);

  for (test = 0; test < count; test++)

    {

      unsigned size_min;

      unsigned size_range;

      mp_size_t an,rn,n;

      mp_size_t itch;

      mp_limb_t p_before, p_after, s_before, s_after;

      for (size_min = 1; (1L << size_min) < MIN_N; size_min++)

	;

      /* We generate an in the MIN_N <= n <= (1 << size_range). */

      size_range = size_min

	+ gmp_urandomm_ui (rands, SIZE_LOG + 1 - size_min);

      n = MIN_N

	+ gmp_urandomm_ui (rands, (1L << size_range) + 1 - MIN_N);

      n = mpn_sqrmod_bnm1_next_size (n);

      if (n == 1)

	an = 1;

      else

	an = ((n+1) >> 1) + gmp_urandomm_ui (rands, (n+1) >> 1);

      mpn_random2 (ap, an);

      /* Sometime trigger the borderline conditions

	 A = -1,0,+1 Mod(B^{n/2}+1).

	 This only makes sense if there is at least a split, i.e. n is even. */

      if ((test & 0x1f) == 1 && (n & 1) == 0) {

	mp_size_t x;

	MPN_COPY (ap, ap + (n >> 1), an - (n >> 1));

	MPN_ZERO (ap + an - (n >> 1) , n - an);

	x = (n == an) ? 0 : gmp_urandomm_ui (rands, n - an);

	ap[x] += gmp_urandomm_ui (rands, 3) - 1;

      }

      rn = MIN(n, 2*an);

      mpn_random2 (pp-1, rn + 2);

      p_before = pp[-1];

      p_after = pp[rn];

      itch = mpn_sqrmod_bnm1_itch (n, an);

      ASSERT_ALWAYS (itch <= mpn_sqrmod_bnm1_itch (MAX_N, MAX_N));

      mpn_random2 (scratch-1, itch+2);

      s_before = scratch[-1];

      s_after = scratch[itch];

      mpn_sqrmod_bnm1 (  pp, n, ap, an, scratch);

      ref_sqrmod_bnm1 (refp, n, ap, an);

      if (pp[-1] != p_before || pp[rn] != p_after

	  || scratch[-1] != s_before || scratch[itch] != s_after

	  || mpn_cmp (refp, pp, rn) != 0)

	{

	  printf ("ERROR in test %d, an = %d, n = %d\n",

		  test, (int) an, (int) n);

	  if (pp[-1] != p_before)

	    {

	      printf ("before pp:"); mpn_dump (pp -1, 1);

	      printf ("keep:   "); mpn_dump (&p_before, 1);

	    }

	  if (pp[rn] != p_after)

	    {

	      printf ("after pp:"); mpn_dump (pp + rn, 1);

	      printf ("keep:   "); mpn_dump (&p_after, 1);

	    }

	  if (scratch[-1] != s_before)

	    {

	      printf ("before scratch:"); mpn_dump (scratch-1, 1);

	      printf ("keep:   "); mpn_dump (&s_before, 1);

	    }

	  if (scratch[itch] != s_after)

	    {

	      printf ("after scratch:"); mpn_dump (scratch + itch, 1);

	      printf ("keep:   "); mpn_dump (&s_after, 1);

	    }

	  mpn_dump (ap, an);

	  mpn_dump (pp, rn);

	  mpn_dump (refp, rn);

	  abort();

	}

    }

  TMP_FREE;

  tests_end ();

  return 0;

}