/* Copyright (C) 1997-2018 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   Contributed by Geoffrey Keating <Geoff.Keating@anu.edu.au>, 1997.

   The GNU C 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 2.1 of the License, or (at your option) any later version.

   The GNU C 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 C Library; if not, see

   <http://www.gnu.org/licenses/>.  */

#include <stdio.h>

#include <math.h>

#include <gmp.h>

#include <string.h>

#include <limits.h>

#include <assert.h>

#define PRINT_ERRORS 0

#define TOL 80

#define N2 17

#define FRAC (32*4)

#define mpbpl (CHAR_BIT * sizeof (mp_limb_t))

#define SZ (FRAC / mpbpl + 1)

typedef mp_limb_t mp1[SZ], mp2[SZ * 2];

/* This string has 101 hex digits.  */

static const char exp1[102] = "2" /* point */

"b7e151628aed2a6abf7158809cf4f3c762e7160f38b4da56a7"

"84d9045190cfef324e7738926cfbe5f4bf8d8d8c31d763da07";

static const char hexdig[] = "0123456789abcdef";

static void

print_mpn_hex (const mp_limb_t *x, unsigned size)

{

   char value[size + 1];

   unsigned i;

   const unsigned final = (size * 4 > SZ * mpbpl) ? SZ * mpbpl / 4 : size;

   memset (value, '0', size);

   for (i = 0; i < final ; i++)

     value[size - 1 - i] = hexdig[x[i * 4 / mpbpl] >> (i * 4) % mpbpl & 0xf];

   value[size] = '\0';

   fputs (value, stdout);

}

static void

exp_mpn (mp1 ex, mp1 x)

{

   unsigned n;

   mp1 xp;

   mp2 tmp;

   mp_limb_t chk __attribute__ ((unused));

   mp1 tol;

   memset (xp, 0, sizeof (mp1));

   memset (ex, 0, sizeof (mp1));

   xp[FRAC / mpbpl] = (mp_limb_t)1 << FRAC % mpbpl;

   memset (tol,0, sizeof (mp1));

   tol[(FRAC - TOL) / mpbpl] = (mp_limb_t)1 << (FRAC - TOL) % mpbpl;

   n = 0;

   do

     {

       /* Calculate sum(x^n/n!) until the next term is sufficiently small.  */

       mpn_mul_n (tmp, xp, x, SZ);

       assert (tmp[SZ * 2 - 1] == 0);

       if (n > 0)

	 mpn_divmod_1 (xp, tmp + FRAC / mpbpl, SZ, n);

       chk = mpn_add_n (ex, ex, xp, SZ);

       assert (chk == 0);

       n++;

       assert (n < 80); /* Catch too-high TOL.  */

     }

   while (n < 10 || mpn_cmp (xp, tol, SZ) >= 0);

}

static int

mpn_bitsize(const mp_limb_t *SRC_PTR, mp_size_t SIZE)

{

   int i, j;

   for (i = SIZE - 1; i > 0; i--)

     if (SRC_PTR[i] != 0)

       break;

   for (j = mpbpl - 1; j >= 0; j--)

     if ((SRC_PTR[i] & (mp_limb_t)1 << j) != 0)

       break;

   return i * mpbpl + j;

}

static int

do_test (void)

{

   mp1 ex, x, xt, e2, e3;

   int i;

   int errors = 0;

   int failures = 0;

   mp1 maxerror;

   int maxerror_s = 0;

   const double sf = pow (2, mpbpl);

   /* assert (mpbpl == mp_bits_per_limb); */

   assert (FRAC / mpbpl * mpbpl == FRAC);

   memset (maxerror, 0, sizeof (mp1));

   memset (xt, 0, sizeof (mp1));

   xt[(FRAC - N2) / mpbpl] = (mp_limb_t)1 << (FRAC - N2) % mpbpl;

   for (i = 0; i < 1 << N2; i++)

   {

      int e2s, e3s, j;

      double de2;

      mpn_mul_1 (x,xt,SZ,i);

      exp_mpn (ex, x);

      de2 = exp (i / (double) (1 << N2));

      for (j = SZ-1; j >= 0; j--)

	{

	  e2[j] = (mp_limb_t) de2;

	  de2 = (de2 - e2[j]) * sf;

	}

      if (mpn_cmp (ex,e2,SZ) >= 0)

	mpn_sub_n (e3,ex,e2,SZ);

      else

	mpn_sub_n (e3,e2,ex,SZ);

      e2s = mpn_bitsize (e2,SZ);

      e3s = mpn_bitsize (e3,SZ);

      if (e3s >= 0 && e2s - e3s < 54)

	{

#if PRINT_ERRORS

	  printf ("%06x ", i * (0x100000 / (1 << N2)));

	  print_mpn_hex (ex, (FRAC / 4) + 1);

	  fputs ("\n       ",stdout);

	  print_mpn_hex (e2, (FRAC / 4) + 1);

	  printf ("\n %c     ",

		  e2s - e3s < 54 ? e2s - e3s == 53 ? 'e' : 'F' : 'P');

	  print_mpn_hex (e3, (FRAC / 4) + 1);

	  putchar ('\n');

#endif

	 errors += (e2s - e3s == 53);

	 failures += (e2s - e3s < 53);

	}

      if (e3s >= maxerror_s

	  && mpn_cmp (e3, maxerror, SZ) > 0)

	{

	  memcpy (maxerror, e3, sizeof (mp1));

	  maxerror_s = e3s;

	}

   }

   /* Check exp_mpn against precomputed value of exp(1).  */

   memset (x, '\0', sizeof (mp1));

   x[FRAC / mpbpl] = (mp_limb_t)1 << FRAC % mpbpl;

   exp_mpn (ex, x);

   memset (e2, '\0', sizeof (mp1));

   for (i = -1; i < 100 && i < FRAC / 4; i++)

     e2[(FRAC - i * 4 - 4) / mpbpl] |= ((mp_limb_t) (strchr (hexdig,

							     exp1[i + 1])

						     - hexdig)

 					<< (FRAC - i * 4 - 4) % mpbpl);

   if (mpn_cmp (ex, e2, SZ) >= 0)

     mpn_sub_n (e3, ex, e2, SZ);

   else

     mpn_sub_n (e3, e2, ex, SZ);

   printf ("%d failures; %d errors; error rate %0.2f%%\n", failures, errors,

	   errors * 100.0 / (double) (1 << N2));

   fputs ("maximum error:   ", stdout);

   print_mpn_hex (maxerror, (FRAC / 4) + 1);

   fputs ("\nerror in exp(1): ", stdout);

   print_mpn_hex (e3, (FRAC / 4) + 1);

   putchar ('\n');

   return failures == 0 ? 0 : 1;

}

#define TIMEOUT 200

#define TEST_FUNCTION do_test ()

#include "../test-skeleton.c"