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/*
Copyright (C) 2018 Fredrik Johansson
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 "longlong.h"
#include "fmpz.h"
void fmpz_fmms(fmpz_t f, const fmpz_t a, const fmpz_t b,
const fmpz_t c, const fmpz_t d)
{
fmpz s, t, u, v;
s = *a;
t = *b;
u = *c;
v = *d;
if (!COEFF_IS_MPZ(s) && !COEFF_IS_MPZ(t) &&
!COEFF_IS_MPZ(u) && !COEFF_IS_MPZ(v))
{
ulong sh, sl, th, tl;
smul_ppmm(sh, sl, s, t);
smul_ppmm(th, tl, u, v);
sub_ddmmss(sh, sl, sh, sl, th, tl);
fmpz_set_signed_uiui(f, sh, sl);
return;
}
if (s == 0 || t == 0)
{
fmpz_mul(f, c, d);
fmpz_neg(f, f);
return;
}
if (u == 0 || v == 0)
{
fmpz_mul(f, a, b);
return;
}
if (f == c || f == d)
{
if (f == a || f == b)
{
fmpz_t t;
fmpz_init(t);
fmpz_mul(t, a, b);
fmpz_submul(t, c, d);
fmpz_swap(t, f);
fmpz_clear(t);
}
else
{
fmpz_mul(f, c, d);
fmpz_submul(f, a, b);
fmpz_neg(f, f);
}
}
else
{
fmpz_mul(f, a, b);
fmpz_submul(f, c, d);
}
}