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/* mpfr_cache -- cache interface for multi-precision const in MPFR.
Copyright 2004, 2005 Free Software Foundation.
This file is part of the MPFR Library.
The MPFR 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 MPFR 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 MPFR Library; see the file COPYING.LIB. If not, write to
the Free Software Foundation, Inc., 51 Franklin Place, Fifth Floor, Boston,
MA 02110-1301, USA. */
#include "mpfr-impl.h"
void
mpfr_init_cache (mpfr_cache_t cache, int (*func)(mpfr_ptr, mp_rnd_t))
{
MPFR_PREC (cache->x) = 0; /* Invalid prec to detect that the cache is not
valid. Maybe add a flag? */
cache->func = func;
}
void
mpfr_clear_cache (mpfr_cache_t cache)
{
if (MPFR_PREC(cache->x) != 0)
mpfr_clear (cache->x);
MPFR_PREC(cache->x) = 0;
}
int
mpfr_cache (mpfr_ptr dest, mpfr_cache_t cache, mp_rnd_t rnd)
{
mp_prec_t prec = MPFR_PREC (dest);
mp_prec_t pold = MPFR_PREC (cache->x);
int inexact, sign;
MPFR_SAVE_EXPO_DECL (expo);
MPFR_SAVE_EXPO_MARK (expo);
/* Check if the cache has been already filled */
if (MPFR_UNLIKELY(pold == 0))
mpfr_init2 (cache->x, prec);
/* Check if we can round with the previous result */
else if (MPFR_LIKELY(prec <= pold))
goto round;
/* Update the cache */
pold = prec /*MPFR_PREC_MIN + prec + __gmpfr_ceil_exp2 (prec)*/;
MPFR_ASSERTD (pold >= prec);
mpfr_prec_round (cache->x, pold, GMP_RNDN);
cache->inexact = (*cache->func) (cache->x, GMP_RNDN);
round:
/* First check if the cache has the exact value (Unlikely)
Else the exact value is between (assuming x=cache->x > 0)
x and x+ulp(x) if cache->inexact < 0
x-ulp(x) and x if cache->inexact > 0
and abs(x-exact) <= ulp(x)/2 */
MPFR_ASSERTD (MPFR_IS_POS(cache->x)); /* TODO...*/
/* We must use nextbelow instead of sub_one_ulp, since we know
that the exact value is < 1/2ulp(x) (We want sub_demi_ulp(x)).
Can't use mpfr_set since we need the even flag. */
sign = MPFR_SIGN (cache->x);
MPFR_SET_EXP (dest, MPFR_GET_EXP (cache->x));
MPFR_SET_SIGN (dest, sign);
MPFR_RNDRAW_EVEN (inexact, dest,
MPFR_MANT (cache->x), MPFR_PREC (cache->x), rnd, sign,
if (MPFR_UNLIKELY ( ++MPFR_EXP (dest) > __gmpfr_emax))
mpfr_overflow (dest, rnd, sign) );
/* inexact = mpfr_set (dest, cache->x, rnd); */
if (MPFR_LIKELY(cache->inexact != 0))
{
switch (rnd)
{
case GMP_RNDZ:
case GMP_RNDD:
if (MPFR_UNLIKELY(inexact == 0))
{
inexact = cache->inexact;
if (inexact > 0)
mpfr_nextbelow (dest);
}
break;
case GMP_RNDU:
if (MPFR_UNLIKELY(inexact == 0))
{
inexact = cache->inexact;
if (inexact < 0)
mpfr_nextabove (dest);
}
break;
default: /* GMP_RNDN */
if (MPFR_UNLIKELY(inexact == MPFR_EVEN_INEX ||
inexact == -MPFR_EVEN_INEX))
{
if (cache->inexact < 0)
mpfr_nextabove (dest);
else
mpfr_nextbelow (dest);
inexact = -inexact;
}
else if (MPFR_UNLIKELY(inexact == 0))
inexact = cache->inexact;
break;
}
}
MPFR_SAVE_EXPO_FREE (expo);
return mpfr_check_range (dest, inexact, rnd);
}
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