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AK: Rename AK::FixedPoint::round to rint and fix a rounding error

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`rint` is a more accurate name for the roudning mode as the fixme above
stated
This commit is contained in:
Hendiadyoin1 2023-07-25 17:53:30 +02:00 • committed by Andrew Kaster
parent 05c959e40b
commit daacc5c6c2
Notes: sideshowbarker 2024-07-16 20:44:03 +09:00
3 changed files with 26 additions and 17 deletions

14
AK/FixedPoint.h
View file

@ -99,17 +99,21 @@ public:
return *this;
}
// Note/FIXME: This uses round to nearest break-tie to even
// Not break-tie away from 0 as the C99's round does
constexpr This round() const
constexpr This rint() const
{
// Note: Round fair, break tie to even
Underlying value = m_value >> precision;
// Note: For negative numbers the ordering are reversed,
// and they were already decremented by the shift, so we need to
// add 1 when we see a fract values behind the `.5`s place set,
// because that means they are smaller than .5
// fract(m_value) >= .5?
if (m_value & (1u << (precision - 1))) {
// fract(m_value) > .5?
if (m_value & (radix_mask >> 2u)) {
// yes: round "up";
value += (m_value > 0 ? 1 : -1);
value += 1;
} else {
// no: round to even;
value += value & 1;
@ -134,7 +138,7 @@ public:
: 0));
}
constexpr Underlying lround() const { return round().raw() >> precision; }
constexpr Underlying lrint() const { return rint().raw() >> precision; }
constexpr Underlying lfloor() const { return m_value >> precision; }
constexpr Underlying lceil() const
{

21
Tests/AK/TestFixedPoint.cpp
View file

@ -38,46 +38,51 @@ TEST_CASE(arithmetic)
TEST_CASE(rounding)
{
EXPECT_EQ(Type(0.5).round(), Type(0));
EXPECT_EQ(Type(0.5).rint(), Type(0));
EXPECT_EQ(Type(0.5).floor(), Type(0));
EXPECT_EQ(Type(0.5).ceil(), Type(1));
EXPECT_EQ(Type(0.75).trunc(), Type(0));
EXPECT_EQ(Type(1.5).round(), Type(2));
EXPECT_EQ(Type(1.5).rint(), Type(2));
EXPECT_EQ(Type(1.5).floor(), Type(1));
EXPECT_EQ(Type(1.5).ceil(), Type(2));
EXPECT_EQ(Type(1.25).trunc(), Type(1));
EXPECT_EQ(Type(-0.5).round(), Type(0));
EXPECT_EQ(Type(-0.5).rint(), Type(0));
EXPECT_EQ(Type(-0.5).floor(), Type(-1));
EXPECT_EQ(Type(-0.5).ceil(), Type(0));
EXPECT_EQ(Type(-0.75).trunc(), Type(0));
EXPECT_EQ(Type(-1.5).round(), Type(-2));
EXPECT_EQ(Type(-1.5).rint(), Type(-2));
EXPECT_EQ(Type(-1.5).floor(), Type(-2));
EXPECT_EQ(Type(-1.5).ceil(), Type(-1));
EXPECT_EQ(Type(-1.25).trunc(), Type(-1));
EXPECT_EQ(Type(0.5).lround(), 0);
EXPECT_EQ(Type(0.5).lrint(), 0);
EXPECT_EQ(Type(0.5).lfloor(), 0);
EXPECT_EQ(Type(0.5).lceil(), 1);
EXPECT_EQ(Type(0.5).ltrunc(), 0);
EXPECT_EQ(Type(1.5).lround(), 2);
EXPECT_EQ(Type(1.5).lrint(), 2);
EXPECT_EQ(Type(1.5).lfloor(), 1);
EXPECT_EQ(Type(1.5).lceil(), 2);
EXPECT_EQ(Type(1.5).ltrunc(), 1);
EXPECT_EQ(Type(-0.5).lround(), 0);
EXPECT_EQ(Type(-0.5).lrint(), 0);
EXPECT_EQ(Type(-0.5).lfloor(), -1);
EXPECT_EQ(Type(-0.5).lceil(), 0);
EXPECT_EQ(Type(-0.5).ltrunc(), 0);
EXPECT_EQ(Type(-1.5).lround(), -2);
EXPECT_EQ(Type(-1.5).lrint(), -2);
EXPECT_EQ(Type(-1.5).lfloor(), -2);
EXPECT_EQ(Type(-1.5).lceil(), -1);
EXPECT_EQ(Type(-1.5).ltrunc(), -1);
EXPECT_EQ(Type(-1.6).rint(), -2);
EXPECT_EQ(Type(-1.4).rint(), -1);
EXPECT_EQ(Type(1.6).rint(), 2);
EXPECT_EQ(Type(1.4).rint(), 1);
// Check that sRGB TRC curve parameters match the s15fixed16 values stored in Gimp's built-in profile.
// (This only requires that the FixedPoint<> constructor rounds before truncating to the fixed-point value,
// as it should anyways.)

8
Tests/LibEDID/TestEDID.cpp
View file

@ -131,7 +131,7 @@ TEST_CASE(edid1)
EXPECT(block_id == expected_timings.block_id);
EXPECT(detailed_timing.horizontal_addressable_pixels() == expected_timings.width);
EXPECT(detailed_timing.vertical_addressable_lines() == expected_timings.height);
EXPECT(detailed_timing.refresh_rate().lround() == expected_timings.refresh_rate);
EXPECT(detailed_timing.refresh_rate().lrint() == expected_timings.refresh_rate);
detailed_timings_found++;
return IterationDecision::Continue;
}));
@ -313,7 +313,7 @@ TEST_CASE(edid2)
EXPECT(block_id == expected_timings.block_id);
EXPECT(detailed_timing.horizontal_addressable_pixels() == expected_timings.width);
EXPECT(detailed_timing.vertical_addressable_lines() == expected_timings.height);
EXPECT(detailed_timing.refresh_rate().lround() == expected_timings.refresh_rate);
EXPECT(detailed_timing.refresh_rate().lrint() == expected_timings.refresh_rate);
detailed_timings_found++;
return IterationDecision::Continue;
}));
@ -430,7 +430,7 @@ TEST_CASE(edid_extension_maps)
EXPECT(block_id == expected_timings.block_id);
EXPECT(detailed_timing.horizontal_addressable_pixels() == expected_timings.width);
EXPECT(detailed_timing.vertical_addressable_lines() == expected_timings.height);
EXPECT(detailed_timing.refresh_rate().lround() == expected_timings.refresh_rate);
EXPECT(detailed_timing.refresh_rate().lrint() == expected_timings.refresh_rate);
detailed_timings_found++;
return IterationDecision::Continue;
}));
@ -479,7 +479,7 @@ TEST_CASE(edid_1_0)
EXPECT(block_id == expected_timings.block_id);
EXPECT(detailed_timing.horizontal_addressable_pixels() == expected_timings.width);
EXPECT(detailed_timing.vertical_addressable_lines() == expected_timings.height);
EXPECT(detailed_timing.refresh_rate().lround() == expected_timings.refresh_rate);
EXPECT(detailed_timing.refresh_rate().lrint() == expected_timings.refresh_rate);
detailed_timings_found++;
return IterationDecision::Continue;
}));