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Bug 796949 - Fix division and rounding of zero.

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Fix division of 128-bit integers so that the remainder inherits the dividend's sign.
Fix rounding for truncated zero.
pull/502/head
David Palma 7 years ago
parent 94c5fe9f1d
commit aab89065da
No known key found for this signature in database
GPG Key ID: 63145C0FAA3BC352
4 changed files with 124 additions and 33 deletions
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56
libgnucash/engine/gnc-int128.cpp
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@ -71,7 +71,7 @@ GncInt128::GncInt128 (int64_t upper, int64_t lower, uint8_t flags) :
m_lo {static_cast<uint64_t>(lower < 0 ? -lower : lower)}
{
if ((upper < 0 && lower > 0) || (upper > 0 && lower < 0))
m_lo = (m_hi << 63) - m_lo;
m_lo = (m_hi << 63) - m_lo;
else
m_lo += (m_hi << 63);
@ -142,7 +142,7 @@ GncInt128::operator int64_t() const
GncInt128::operator uint64_t() const
{
auto flags = get_flags(m_hi);
if (flags & neg)
if ((flags & neg) && !isZero()) // exclude negative zero
throw std::underflow_error ("Can't represent negative value as uint64_t");
if ((flags & (overflow | NaN)) || (m_hi || m_lo > UINT64_MAX))
throw std::overflow_error ("Value to large to represent as uint64_t");
@ -160,14 +160,15 @@ GncInt128::cmp (const GncInt128& b) const noexcept
return 1;
auto hi = get_num(m_hi);
auto bhi = get_num(b.m_hi);
if (isZero() && b.isZero()) return 0;
if (flags & neg)
{
if (!b.isNeg()) return -1;
if (hi > bhi) return -1;
if (hi < bhi) return 1;
if (m_lo > b.m_lo) return -1;
if (m_lo < b.m_lo) return 1;
return 0;
if (!b.isNeg()) return -1;
if (hi > bhi) return -1;
if (hi < bhi) return 1;
if (m_lo > b.m_lo) return -1;
if (m_lo < b.m_lo) return 1;
return 0;
}
if (b.isNeg()) return 1;
if (hi < bhi) return -1;
@ -309,9 +310,9 @@ GncInt128::operator-() const noexcept
auto retval = *this;
auto flags = get_flags(retval.m_hi);
if (isNeg())
flags ^= neg;
flags ^= neg;
else
flags |= neg;
flags |= neg;
retval.m_hi = set_flags(retval.m_hi, flags);
return retval;
}
@ -357,7 +358,7 @@ GncInt128::operator+= (const GncInt128& b) noexcept
if (isOverflow() || isNan())
return *this;
if ((isNeg () && !b.isNeg ()) || (!isNeg () && b.isNeg ()))
return this->operator-= (-b);
return this->operator-= (-b);
uint64_t result = m_lo + b.m_lo;
uint64_t carry = static_cast<int64_t>(result < m_lo); //Wrapping
m_lo = result;
@ -365,7 +366,7 @@ GncInt128::operator+= (const GncInt128& b) noexcept
auto bhi = get_num(b.m_hi);
result = hi + bhi + carry;
if (result < hi || result & flagmask)
flags |= overflow;
flags |= overflow;
m_hi = set_flags(result, flags);
return *this;
}
@ -439,7 +440,7 @@ GncInt128::operator-= (const GncInt128& b) noexcept
return *this;
if ((!isNeg() && b.isNeg()) || (isNeg() && !b.isNeg()))
return this->operator+= (-b);
return this->operator+= (-b);
bool operand_bigger {abs().cmp (b.abs()) < 0};
auto hi = get_num(m_hi);
auto far_hi = get_num(b.m_hi);
@ -478,6 +479,8 @@ GncInt128::operator*= (const GncInt128& b) noexcept
{
/* Test for 0 first */
auto flags = get_flags(m_hi);
/* Handle the sign; ^ flips if b is negative */
flags ^= (get_flags(b.m_hi) & neg);
if (isZero() || b.isZero())
{
m_lo = 0;
@ -514,8 +517,7 @@ GncInt128::operator*= (const GncInt128& b) noexcept
m_hi = set_flags(m_hi, flags);
return *this;
}
/* Handle the sign; ^ flips if b is negative */
flags ^= (get_flags(b.m_hi) & neg);
/* The trivial case */
if (abits + bbits <= legbits)
{
@ -602,6 +604,7 @@ div_multi_leg (uint64_t* u, size_t m, uint64_t* v, size_t n,
uint64_t d {(UINT64_C(1) << sublegbits)/(v[n - 1] + UINT64_C(1))};
uint64_t carry {UINT64_C(0)};
bool negative {q.isNeg()};
bool rnegative {r.isNeg()};
for (size_t i = 0; i < m; ++i)
{
u[i] = u[i] * d + carry;
@ -689,6 +692,7 @@ div_multi_leg (uint64_t* u, size_t m, uint64_t* v, size_t n,
r = GncInt128 ((u[3] << sublegbits) + u[2], (u[1] << sublegbits) + u[0]);
r /= d;
if (negative) q = -q;
if (rnegative) r = -r;
}
void
@ -698,6 +702,7 @@ div_single_leg (uint64_t* u, size_t m, uint64_t v,
uint64_t qv[sublegs] {};
uint64_t carry {};
bool negative {q.isNeg()};
bool rnegative {r.isNeg()};
for (int i = m - 1; i >= 0; --i)
{
qv[i] = u[i] / v;
@ -713,13 +718,18 @@ div_single_leg (uint64_t* u, size_t m, uint64_t v,
q = GncInt128 ((qv[3] << sublegbits) + qv[2], (qv[1] << sublegbits) + qv[0]);
r = GncInt128 ((u[3] << sublegbits) + u[2], (u[1] << sublegbits) + u[0]);
if (negative) q = -q;
if (rnegative) r = -r;
}
}// namespace
void
void
GncInt128::div (const GncInt128& b, GncInt128& q, GncInt128& r) const noexcept
{
// clear remainder and quotient
r = GncInt128(0);
q = GncInt128(0);
auto qflags = get_flags(q.m_hi);
auto rflags = get_flags(r.m_hi);
if (isOverflow() || b.isOverflow())
@ -745,6 +755,7 @@ GncInt128::div (const GncInt128& b, GncInt128& q, GncInt128& r) const noexcept
assert (&r != &b);
q.zero(), r.zero();
qflags = rflags = 0;
if (b.isZero())
{
qflags |= NaN;
@ -755,11 +766,17 @@ GncInt128::div (const GncInt128& b, GncInt128& q, GncInt128& r) const noexcept
}
if (isNeg())
{
qflags |= neg;
rflags |= neg; // the remainder inherits the dividend's sign
}
if (b.isNeg())
qflags ^= neg;
q.m_hi = set_flags(q.m_hi, qflags);
r.m_hi = set_flags(r.m_hi, rflags);
if (abs() < b.abs())
{
r = *this;
@ -767,7 +784,7 @@ GncInt128::div (const GncInt128& b, GncInt128& q, GncInt128& r) const noexcept
}
auto hi = get_num(m_hi);
auto bhi = get_num(b.m_hi);
q.m_hi = set_flags(hi, qflags);
if (hi == 0 && bhi == 0) //let the hardware do it
{
assert (b.m_lo != 0); // b.m_hi is 0 but b isn't or we didn't get here.
@ -914,6 +931,11 @@ GncInt128::asCharBufR(char* buf) const noexcept
sprintf (buf, "%s", "NaN");
return buf;
}
if (isZero())
{
sprintf (buf, "%d", 0);
return buf;
}
uint64_t d[dec_array_size] {};
decimal_from_binary(d, get_num(m_hi), m_lo);
char* next = buf;

71
libgnucash/engine/gnc-rational-rounding.hpp
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@ -25,6 +25,12 @@
#include "gnc-numeric.h"
#include "gnc-int128.hpp"
template <typename T> inline bool
quotient_is_positive(T dividend, T divisor)
{
return (dividend > 0 && divisor > 0) || (dividend < 0 && divisor < 0);
}
enum class RoundType
{
floor = GNC_HOW_RND_FLOOR,
@ -72,8 +78,23 @@ round(T num, T den, T rem, RT2T<RoundType::floor>)
// << ", and rem " << rem << ".\n";
if (rem == 0)
return num;
if (num < 0)
return num + 1;
// floor num==0 that is the quotient of two numbers with opposite signs
if (num < 0 || (num == 0 && !quotient_is_positive(rem, den)))
return num - 1;
return num;
}
template <> inline GncInt128
round<GncInt128>(GncInt128 num, GncInt128 den, GncInt128 rem,
RT2T<RoundType::floor>)
{
// std::cout << "Rounding to floor with num " << num << " den " << den
// << ", and rem " << rem << ".\n";
if (rem == 0)
return num;
if (num.isNeg())
return num - 1;
return num;
}
@ -82,7 +103,18 @@ round(T num, T den, T rem, RT2T<RoundType::ceiling>)
{
if (rem == 0)
return num;
if (num > 0)
if (num > 0 || (num == 0 && quotient_is_positive(rem, den)))
return num + 1;
return num;
}
template <> inline GncInt128
round<GncInt128>(GncInt128 num, GncInt128 den, GncInt128 rem,
RT2T<RoundType::ceiling>)
{
if (rem == 0)
return num;
if (!num.isNeg())
return num + 1;
return num;
}
@ -98,16 +130,31 @@ round(T num, T den, T rem, RT2T<RoundType::promote>)
{
if (rem == 0)
return num;
if (num == 0)
return (!quotient_is_positive(rem, den) ? -1 : 1);
return num + (num < 0 ? -1 : 1);
}
template <> inline GncInt128
round<GncInt128>(GncInt128 num, GncInt128 den, GncInt128 rem,
RT2T<RoundType::promote>)
{
if (rem == 0)
return num;
return num + (num.isNeg() ? -1 : 1);
}
template <typename T> inline T
round(T num, T den, T rem, RT2T<RoundType::half_down>)
{
if (rem == 0)
return num;
if (std::abs(rem * 2) > std::abs(den))
{
if (num == 0)
return (!quotient_is_positive(rem, den) ? -1 : 1);
return num + (num < 0 ? -1 : 1);
}
return num;
}
@ -118,7 +165,7 @@ round<GncInt128>(GncInt128 num, GncInt128 den, GncInt128 rem,
if (rem == 0)
return num;
if (rem.abs() * 2 > den.abs())
return num + (num < 0 ? -1 : 1);
return num + (num.isNeg() ? -1 : 1);
return num;
}
@ -128,7 +175,11 @@ round(T num, T den, T rem, RT2T<RoundType::half_up>)
if (rem == 0)
return num;
if (std::abs(rem) * 2 >= std::abs(den))
{
if (num == 0)
return (!quotient_is_positive(rem, den) ? -1 : 1);
return num + (num < 0 ? -1 : 1);
}
return num;
}
@ -139,7 +190,7 @@ round<GncInt128>(GncInt128 num, GncInt128 den, GncInt128 rem,
if (rem == 0)
return num;
if (rem.abs() * 2 >= den.abs())
return num + (num < 0 ? -1 : 1);
return num + (num.isNeg() ? -1 : 1);
return num;
}
@ -150,11 +201,15 @@ round(T num, T den, T rem, RT2T<RoundType::bankers>)
return num;
if (std::abs(rem * 2) > std::abs(den) ||
(std::abs(rem * 2) == std::abs(den) && num % 2))
return num += (num < 0 ? -1 : 1);
{
if (num == 0)
return (!quotient_is_positive(rem, den) ? -1 : 1);
return num + (num < 0 ? -1 : 1);
}
return num;
}
template<> inline GncInt128
template <> inline GncInt128
round<GncInt128>(GncInt128 num, GncInt128 den, GncInt128 rem,
RT2T<RoundType::bankers>)
{
@ -162,7 +217,7 @@ round<GncInt128>(GncInt128 num, GncInt128 den, GncInt128 rem,
return num;
if (rem.abs() * 2 > den.abs() ||
(rem.abs() * 2 == den.abs() && num % 2))
return num += (num < 0 ? -1 : 1);
return num + (num.isNeg() ? -1 : 1);
return num;
}
#endif //__GNC_RATIONAL_ROUNDING_HPP__

28
libgnucash/engine/test/gtest-gnc-int128.cpp
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@ -432,7 +432,7 @@ TEST(GncInt128_functions, divide)
GncInt128 big (sarg, barg);
GncInt128 bigger (static_cast<uint64_t>(sarg), uarg);
GncInt128 nsmall = -small;
GncInt128 nbig = -bigger;
GncInt128 nbigger = -bigger;
EXPECT_EQ (GncInt128(INT64_C(0)), zero /= smallest);
EXPECT_EQ (GncInt128(INT64_C(0)), zero %= smallest);
@ -451,11 +451,20 @@ TEST(GncInt128_functions, divide)
nsmall.div (smaller, q, r);
EXPECT_EQ (-two, q);
EXPECT_EQ (GncInt128(INT64_C(3810195028972355394)), r);
EXPECT_EQ (GncInt128(INT64_C(-3810195028972355394)), r);
nsmall.div (-smaller, q, r);
EXPECT_EQ (two, q);
EXPECT_EQ (GncInt128(INT64_C(3810195028972355394)), r);
EXPECT_EQ (GncInt128(INT64_C(-3810195028972355394)), r);
smaller.div (small, q, r);
EXPECT_EQ (zero, q);
EXPECT_EQ (smaller, r);
smaller.div (nsmall, q, r);
EXPECT_EQ (zero, q);
EXPECT_TRUE (q.isNeg());
EXPECT_EQ (smaller, r);
bigger.div (bigger, q, r);
EXPECT_EQ (one, q);
@ -477,18 +486,23 @@ TEST(GncInt128_functions, divide)
EXPECT_EQ (-two, q);
EXPECT_EQ (GncInt128(UINT64_C(3810195028972355394)), r);
nbig.div (-big, q, r);
nbigger.div (-big, q, r);
EXPECT_EQ (two, q);
EXPECT_EQ (GncInt128(UINT64_C(3810195028972355394)), r);
EXPECT_EQ (GncInt128(0, UINT64_C(3810195028972355394), GncInt128::neg), r);
nbig.div (-big, q, r);
nbigger.div (-big, q, r);
EXPECT_EQ (two, q);
EXPECT_EQ (GncInt128(UINT64_C(3810195028972355394)), r);
EXPECT_EQ (GncInt128(0, UINT64_C(3810195028972355394), GncInt128::neg), r);
big.div (bigger, q, r);
EXPECT_EQ (zero, q);
EXPECT_EQ (big, r);
big.div (nbigger, q, r);
EXPECT_EQ (zero, q);
EXPECT_TRUE (q.isNeg());
EXPECT_EQ (big, r);
big.div (big - 1, q, r);
EXPECT_EQ(one, q);
EXPECT_EQ(one, r);

2
libgnucash/engine/test/gtest-gnc-numeric.cpp
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@ -411,7 +411,7 @@ TEST(gncnumeric_functions, test_convert)
EXPECT_EQ(3465453, c.num());
EXPECT_EQ(128, c.denom());
ASSERT_NO_THROW(c = b.convert<RoundType::floor>(128));
EXPECT_EQ(-3465452, c.num());
EXPECT_EQ(-3465454, c.num());
EXPECT_EQ(128, c.denom());
ASSERT_NO_THROW(c = a.convert<RoundType::ceiling>(128));
EXPECT_EQ(3465454, c.num());

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