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/* mpfr_cache -- cache interface for multiple-precision constants in MPFR.
Copyright 2004-2018 Free Software Foundation, Inc.
Contributed by the AriC and Caramba projects, INRIA.
This file is part of the GNU MPFR Library.
The GNU 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 3 of the License, or (at your
option) any later version.
The GNU 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 GNU MPFR Library; see the file COPYING.LESSER. If not, see
http://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc.,
51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */
#include "mpfr-impl.h"
#if 0 /* this function is not used/documented/tested so far, it could be
useful if some user wants to add a new constant to mpfr, and
implement a cache mechanism for that constant */
void
mpfr_init_cache (mpfr_cache_t cache, int (*func)(mpfr_ptr, mpfr_rnd_t))
{
MPFR_PREC (cache->x) = 0; /* Invalid prec to detect that the cache is not
valid. Maybe add a flag? */
cache->func = func;
}
#endif
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, mpfr_rnd_t rnd)
{
mpfr_prec_t prec = MPFR_PREC (dest);
mpfr_prec_t pold = MPFR_PREC (cache->x);
int inexact, sign;
MPFR_SAVE_EXPO_DECL (expo);
MPFR_SAVE_EXPO_MARK (expo);
if (MPFR_UNLIKELY (prec > pold))
{
/* No previous result in the cache or the precision of the
previous result is not sufficient. */
if (MPFR_UNLIKELY (pold == 0)) /* No previous result. */
mpfr_init2 (cache->x, prec);
/* Update the cache. */
pold = prec;
/* no need to keep the previous value */
mpfr_set_prec (cache->x, pold);
cache->inexact = (*cache->func) (cache->x, MPFR_RNDN);
}
/* now pold >= prec is the precision of cache->x */
/* 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. */
/* we assume all cached constants are positive */
MPFR_ASSERTN (MPFR_IS_POS (cache->x)); /* TODO... */
sign = MPFR_SIGN (cache->x);
MPFR_SET_EXP (dest, MPFR_GET_EXP (cache->x));
MPFR_SET_SIGN (dest, sign);
/* round cache->x from precision pold down to precision prec */
MPFR_RNDRAW_GEN (inexact, dest,
MPFR_MANT (cache->x), pold, rnd, sign,
if (MPFR_UNLIKELY (cache->inexact == 0))
{
if ((_sp[0] & _ulp) == 0)
{
inexact = -sign;
goto trunc_doit;
}
else
goto addoneulp;
}
else if (cache->inexact < 0)
goto addoneulp;
else /* cache->inexact > 0 */
{
inexact = -sign;
goto trunc_doit;
},
if (MPFR_UNLIKELY (++MPFR_EXP (dest) > __gmpfr_emax))
mpfr_overflow (dest, rnd, sign);
);
if (MPFR_LIKELY (cache->inexact != 0))
{
switch (rnd)
{
case MPFR_RNDZ:
case MPFR_RNDD:
if (MPFR_UNLIKELY (inexact == 0))
{
inexact = cache->inexact;
if (inexact > 0)
{
mpfr_nextbelow (dest);
inexact = -inexact;
}
}
break;
case MPFR_RNDU:
case MPFR_RNDA:
if (MPFR_UNLIKELY (inexact == 0))
{
inexact = cache->inexact;
if (inexact < 0)
{
mpfr_nextabove (dest);
inexact = -inexact;
}
}
break;
default: /* MPFR_RNDN */
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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