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New implementations of fp.roundToIntegral in mpf and fpa2bv.

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Partially fixes #69
This commit is contained in:
Christoph M. Wintersteiger 2015-05-06 19:18:29 +01:00
parent 53b479e1c3
commit a63481de85
4 changed files with 168 additions and 58 deletions
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31
src/util/mpf.cpp
View file

@ -1004,26 +1004,29 @@ void mpf_manager::round_to_integral(mpf_rounding_mode rm, mpf const & x, mpf & o
else if (is_inf(x))
set(o, x);
else if (is_zero(x))
mk_zero(x.ebits, x.sbits, x.sign, o);
mk_zero(x.ebits, x.sbits, x.sign, o); // -0.0 -> -0.0, says IEEE754, Sec 5.9.
else if (x.exponent < 0) {
if (rm == MPF_ROUND_TOWARD_ZERO ||
rm == MPF_ROUND_TOWARD_NEGATIVE)
mk_pzero(x.ebits, x.sbits, o);
mk_zero(x.ebits, x.sbits, x.sign, o);
else if (rm == MPF_ROUND_NEAREST_TEVEN ||
rm == MPF_ROUND_NEAREST_TAWAY) {
bool tie = m_mpz_manager.is_zero(x.significand) && x.exponent == -1;
if (tie && rm == MPF_ROUND_NEAREST_TEVEN)
mk_pzero(x.ebits, x.sbits, o);
mk_zero(x.ebits, x.sbits, x.sign, o);
else if (tie && rm == MPF_ROUND_NEAREST_TAWAY)
mk_one(x.ebits, x.sbits, o);
else if (x.exponent < -1 || m_mpz_manager.lt(x.significand, m_powers2(x.sbits-2)))
mk_pzero(x.ebits, x.sbits, o);
mk_one(x.ebits, x.sbits, x.sign, o);
else if (x.exponent < -1)
mk_zero(x.ebits, x.sbits, x.sign, o);
else
mk_one(x.ebits, x.sbits, o);
mk_one(x.ebits, x.sbits, x.sign, o);
}
else {
SASSERT(rm == MPF_ROUND_TOWARD_POSITIVE);
mk_one(x.ebits, x.sbits, o);
if (x.sign)
mk_nzero(x.ebits, x.sbits, o);
else
mk_one(x.ebits, x.sbits, false, o);
}
}
else if (x.exponent >= x.sbits - 1)
@ -1049,7 +1052,7 @@ void mpf_manager::round_to_integral(mpf_rounding_mode rm, mpf const & x, mpf & o
unsigned shift = o.sbits - ((unsigned)o.exponent) - 1;
const mpz & shift_p = m_powers2(shift);
TRACE("mpf_dbg", tout << "shift=" << shift << std::endl;);
TRACE("mpf_dbg", tout << "shift=" << shift << std::endl;);
scoped_mpz div(m_mpz_manager), rem(m_mpz_manager);
m_mpz_manager.machine_div_rem(o.significand, shift_p, div, rem);
@ -1065,16 +1068,16 @@ void mpf_manager::round_to_integral(mpf_rounding_mode rm, mpf const & x, mpf & o
(rm == MPF_ROUND_NEAREST_TEVEN && m_mpz_manager.is_odd(div)) ||
(rm == MPF_ROUND_NEAREST_TAWAY && m_mpz_manager.is_even(div)))
m_mpz_manager.inc(div);
else if (m_mpz_manager.gt(t, shift_p))
else if (x.sign ^ m_mpz_manager.gt(t, shift_p))
m_mpz_manager.inc(div);
break;
}
case MPF_ROUND_TOWARD_POSITIVE:
if (!m_mpz_manager.is_zero(rem) && !o.sign)
if (!m_mpz_manager.is_zero(rem) && o.sign)
m_mpz_manager.inc(div);
break;
case MPF_ROUND_TOWARD_NEGATIVE:
if (!m_mpz_manager.is_zero(rem) && o.sign)
if (!m_mpz_manager.is_zero(rem) && !o.sign)
m_mpz_manager.inc(div);
break;
case MPF_ROUND_TOWARD_ZERO:
@ -1511,10 +1514,10 @@ void mpf_manager::mk_nan(unsigned ebits, unsigned sbits, mpf & o) {
o.sign = false;
}
void mpf_manager::mk_one(unsigned ebits, unsigned sbits, mpf & o) const {
void mpf_manager::mk_one(unsigned ebits, unsigned sbits, bool sign, mpf & o) const {
o.sbits = sbits;
o.ebits = ebits;
o.sign = false;
o.sign = sign;
m_mpz_manager.set(o.significand, 0);
o.exponent = 0;
}

2
src/util/mpf.h
View file

@ -209,7 +209,7 @@ public:
void to_sbv_mpq(mpf_rounding_mode rm, const mpf & x, scoped_mpq & o);
protected:
void mk_one(unsigned ebits, unsigned sbits, mpf & o) const;
void mk_one(unsigned ebits, unsigned sbits, bool sign, mpf & o) const;
bool has_bot_exp(mpf const & x);
bool has_top_exp(mpf const & x);