/* Implementation of the squaring algorithm with Toom-Cook 6.5-way.

   Contributed to the GNU project by Marco Bodrato.

   THE FUNCTION IN THIS FILE IS INTERNAL WITH A MUTABLE INTERFACE.  IT IS ONLY
   SAFE TO REACH IT THROUGH DOCUMENTED INTERFACES.  IN FACT, IT IS ALMOST
   GUARANTEED THAT IT WILL CHANGE OR DISAPPEAR IN A FUTURE GNU MP RELEASE.

Copyright 2009 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 "gmp.h"
#include "gmp-impl.h"


#if GMP_NUMB_BITS < 21
#error Not implemented.
#endif


#if TUNE_PROGRAM_BUILD
#define MAYBE_sqr_basecase 1
#define MAYBE_sqr_above_basecase   1
#define MAYBE_sqr_toom2   1
#define MAYBE_sqr_above_toom2   1
#define MAYBE_sqr_toom3   1
#define MAYBE_sqr_above_toom3   1
#define MAYBE_sqr_above_toom4   1
#else
#ifdef  SQR_TOOM8_THRESHOLD
#define SQR_TOOM6_MAX ((SQR_TOOM8_THRESHOLD+6*2-1+5)/6)
#else
#define SQR_TOOM6_MAX					\
  ((SQR_FFT_THRESHOLD <= MP_SIZE_T_MAX - (6*2-1+5)) ?	\
   ((SQR_FFT_THRESHOLD+6*2-1+5)/6)			\
   : MP_SIZE_T_MAX )
#endif
#define MAYBE_sqr_basecase					\
  (SQR_TOOM6_THRESHOLD < 6 * SQR_TOOM2_THRESHOLD)
#define MAYBE_sqr_above_basecase				\
  (SQR_TOOM6_MAX >=  SQR_TOOM2_THRESHOLD)
#define MAYBE_sqr_toom2						\
  (SQR_TOOM6_THRESHOLD < 6 * SQR_TOOM3_THRESHOLD)
#define MAYBE_sqr_above_toom2					\
  (SQR_TOOM6_MAX >= SQR_TOOM3_THRESHOLD)
#define MAYBE_sqr_toom3						\
  (SQR_TOOM6_THRESHOLD < 6 * SQR_TOOM4_THRESHOLD)
#define MAYBE_sqr_above_toom3					\
  (SQR_TOOM6_MAX >= SQR_TOOM4_THRESHOLD)
#define MAYBE_sqr_above_toom4					\
  (SQR_TOOM6_MAX >= SQR_TOOM6_THRESHOLD)
#endif

#define TOOM6_SQR_REC(p, a, n, ws)					\
  do {									\
    if (MAYBE_sqr_basecase && ( !MAYBE_sqr_above_basecase		\
	|| BELOW_THRESHOLD (n, SQR_TOOM2_THRESHOLD)))			\
      mpn_sqr_basecase (p, a, n);					\
    else if (MAYBE_sqr_toom2 && ( !MAYBE_sqr_above_toom2		\
	     || BELOW_THRESHOLD (n, SQR_TOOM3_THRESHOLD)))		\
      mpn_toom2_sqr (p, a, n, ws);					\
    else if (MAYBE_sqr_toom3 && ( !MAYBE_sqr_above_toom3		\
	     || BELOW_THRESHOLD (n, SQR_TOOM4_THRESHOLD)))		\
      mpn_toom3_sqr (p, a, n, ws);					\
    else if (! MAYBE_sqr_above_toom4					\
	     || BELOW_THRESHOLD (n, SQR_TOOM6_THRESHOLD))		\
      mpn_toom4_sqr (p, a, n, ws);					\
    else								\
      mpn_toom6_sqr (p, a, n, ws);					\
  } while (0)

void
mpn_toom6_sqr  (mp_ptr pp, mp_srcptr ap, mp_size_t an, mp_ptr scratch)
{
  mp_size_t n, s;

  /***************************** decomposition *******************************/

  ASSERT( an >= 18 );

  n = 1 + (an - 1) / (size_t) 6;

  s = an - 5 * n;

  ASSERT (0 < s && s <= n);

#define   r4    (pp + 3 * n)			/* 3n+1 */
#define   r2    (pp + 7 * n)			/* 3n+1 */
#define   r0    (pp +11 * n)			/* s+t <= 2*n */
#define   r5    (scratch)			/* 3n+1 */
#define   r3    (scratch + 3 * n + 1)		/* 3n+1 */
#define   r1    (scratch + 6 * n + 2)		/* 3n+1 */
#define   v0    (pp + 7 * n)			/* n+1 */
#define   v2    (pp + 9 * n+2)			/* n+1 */
#define   wse   (scratch + 9 * n + 3)		/* 3n+1 */

  /* Alloc also 3n+1 limbs for ws... toom_interpolate_12pts may
     need all of them, when DO_mpn_sublsh_n usea a scratch  */
/*   if (scratch== NULL) */
/*     scratch = TMP_SALLOC_LIMBS (12 * n + 6); */

  /********************** evaluation and recursive calls *********************/
  /* $\pm1/2$ */
  mpn_toom_eval_pm2rexp (v2, v0, 5, ap, n, s, 1, pp);
  TOOM6_SQR_REC(pp, v0, n + 1, wse); /* A(-1/2)*B(-1/2)*2^. */
  TOOM6_SQR_REC(r5, v2, n + 1, wse); /* A(+1/2)*B(+1/2)*2^. */
  mpn_toom_couple_handling (r5, 2 * n + 1, pp, 0, n, 1, 0);

  /* $\pm1$ */
  mpn_toom_eval_pm1 (v2, v0, 5, ap, n, s,    pp);
  TOOM6_SQR_REC(pp, v0, n + 1, wse); /* A(-1)*B(-1) */
  TOOM6_SQR_REC(r3, v2, n + 1, wse); /* A(1)*B(1) */
  mpn_toom_couple_handling (r3, 2 * n + 1, pp, 0, n, 0, 0);

  /* $\pm4$ */
  mpn_toom_eval_pm2exp (v2, v0, 5, ap, n, s, 2, pp);
  TOOM6_SQR_REC(pp, v0, n + 1, wse); /* A(-4)*B(-4) */
  TOOM6_SQR_REC(r1, v2, n + 1, wse); /* A(+4)*B(+4) */
  mpn_toom_couple_handling (r1, 2 * n + 1, pp, 0, n, 2, 4);

  /* $\pm1/4$ */
  mpn_toom_eval_pm2rexp (v2, v0, 5, ap, n, s, 2, pp);
  TOOM6_SQR_REC(pp, v0, n + 1, wse); /* A(-1/4)*B(-1/4)*4^. */
  TOOM6_SQR_REC(r4, v2, n + 1, wse); /* A(+1/4)*B(+1/4)*4^. */
  mpn_toom_couple_handling (r4, 2 * n + 1, pp, 0, n, 2, 0);

  /* $\pm2$ */
  mpn_toom_eval_pm2 (v2, v0, 5, ap, n, s, pp);
  TOOM6_SQR_REC(pp, v0, n + 1, wse); /* A(-2)*B(-2) */
  TOOM6_SQR_REC(r2, v2, n + 1, wse); /* A(+2)*B(+2) */
  mpn_toom_couple_handling (r2, 2 * n + 1, pp, 0, n, 1, 2);

#undef v0
#undef v2

  /* A(0)*B(0) */
  TOOM6_SQR_REC(pp, ap, n, wse);

  mpn_toom_interpolate_12pts (pp, r1, r3, r5, n, 2 * s, 0, wse);

#undef r0
#undef r1
#undef r2
#undef r3
#undef r4
#undef r5

}
#undef TOOM6_SQR_REC
#undef MAYBE_sqr_basecase
#undef MAYBE_sqr_above_basecase
#undef MAYBE_sqr_toom2
#undef MAYBE_sqr_above_toom2
#undef MAYBE_sqr_toom3
#undef MAYBE_sqr_above_toom3
#undef MAYBE_sqr_above_toom4
