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/*
Copyright (C) 2011 Fredrik Johansson
Copyright (C) 2024 Albin Ahlbäck
This file is part of FLINT.
FLINT is free software: you can redistribute it and/or modify it under
the terms of the GNU Lesser General Public License (LGPL) as published
by the Free Software Foundation; either version 3 of the License, or
(at your option) any later version. See <https://www.gnu.org/licenses/>.
*/
#include "test_helpers.h"
#include "gmpcompat.h"
#include "ulong_extras.h"
#ifndef n_factorial_mod2_foolproof
#define n_factorial_mod2_foolproof n_factorial_mod2_foolproof
static ulong
n_factorial_mod2_foolproof(ulong n, ulong p, ulong pinv)
{
ulong prod = UWORD(1) % p;
while (n)
{
prod = n_mulmod2_preinv(prod, n, p, pinv);
n--;
}
return prod;
}
#endif
TEST_FUNCTION_START(n_factorial_mod2_preinv, state)
{
slong ix;
for (ix = 0; ix < 1000 * flint_test_multiplier(); ix++)
{
ulong n, p, pinv, x, y;
int type;
type = n_randint(state, 100);
if (type == 0)
{
/* n is big */
n = n_randint(state, 1000000);
}
else
{
/* n is small */
n = n_randint(state, 1000);
}
p = n_randtest_not_zero(state);
pinv = n_preinvert_limb(p);
x = n_factorial_mod2_preinv(n, p, pinv);
y = n_factorial_mod2_foolproof(n, p, pinv);
if (x != y)
TEST_FUNCTION_FAIL(
"n = %wu\n"
"p = %wu\n"
"x = %wu\n"
"y = %wu\n",
n, p, x, y);
}
TEST_FUNCTION_END(state);
}