arb/arf/mul_via_mpfr.c

/*=============================================================================

    This file is part of ARB.

    ARB 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 2 of the License, or
    (at your option) any later version.

    ARB 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 ARB; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA

=============================================================================*/
/******************************************************************************

    Copyright (C) 2014 Fredrik Johansson

******************************************************************************/

#include "arf.h"

int
arf_mul_via_mpfr(arf_ptr z, arf_srcptr x, arf_srcptr y,
        slong prec, arf_rnd_t rnd)
{
    mp_size_t xn, yn, zn, val;
    mp_srcptr xptr, yptr;
    mp_ptr tmp, zptr;
    mpfr_t xf, yf, zf;
    int ret;
    ARF_MUL_TMP_DECL

    if (arf_is_special(x) || arf_is_special(y))
    {
        arf_mul_special(z, x, y);
        return 0;
    }

    ARF_GET_MPN_READONLY(xptr, xn, x);
    ARF_GET_MPN_READONLY(yptr, yn, y);

    prec = FLINT_MIN((xn + yn) * FLINT_BITS, prec);
    zn = (prec + FLINT_BITS - 1) / FLINT_BITS;

    ARF_MUL_TMP_ALLOC(tmp, zn)

    zf->_mpfr_d = tmp;
    zf->_mpfr_prec = prec;
    zf->_mpfr_sign = 1;
    zf->_mpfr_exp = 0;

    xf->_mpfr_d = (mp_ptr) xptr;
    xf->_mpfr_prec = xn * FLINT_BITS;
    xf->_mpfr_sign = ARF_SGNBIT(x) ? -1 : 1;
    xf->_mpfr_exp = 0;

    if (x == y)
    {
        ret = mpfr_sqr(zf, xf, arf_rnd_to_mpfr(rnd));
    }
    else
    {
        yf->_mpfr_d = (mp_ptr) yptr;
        yf->_mpfr_prec = yn * FLINT_BITS;
        yf->_mpfr_sign = ARF_SGNBIT(y) ? -1 : 1;
        yf->_mpfr_exp = 0;

        ret = mpfr_mul(zf, xf, yf, arf_rnd_to_mpfr(rnd));
    }

    ret = (ret != 0);

    _fmpz_add2_fast(ARF_EXPREF(z), ARF_EXPREF(x), ARF_EXPREF(y), zf->_mpfr_exp);

    val = 0;
    while (tmp[val] == 0)
        val++;

    ARF_GET_MPN_WRITE(zptr, zn - val, z);
    flint_mpn_copyi(zptr, tmp + val, zn - val);
    ARF_XSIZE(z) |= (zf->_mpfr_sign < 0);

    ARF_MUL_TMP_FREE(tmp, zn)

    return ret;
}