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Fix wrong integer division where rounding up was intended #1254

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merged 2 commits into from
Oct 6, 2022
Merged

Fix wrong integer division where rounding up was intended #1254

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d518966
[numeric] Introduce divideRoundUp() for integer division with rounding
p12tic Oct 1, 2022
2caea25
[fuseCut] Fix incorrect rounding of integer division result
p12tic Oct 1, 2022
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11 changes: 6 additions & 5 deletions src/aliceVision/fuseCut/DelaunayGraphCut.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -958,8 +958,8 @@ void DelaunayGraphCut::addMaskHelperPoints(const Point3d voxel[8], const StaticV
}
}

int syMax = std::ceil(height / step);
int sxMax = std::ceil(width / step);
int syMax = divideRoundUp(height, step);
int sxMax = divideRoundUp(width, step);

for(int sy = 0; sy < syMax; ++sy)
{
Expand Down Expand Up @@ -1063,7 +1063,8 @@ void DelaunayGraphCut::fuseFromDepthMaps(const StaticVector<int>& cams, const Po
{
const auto& imgParams = _mp.getImageParams(i);
startIndex[i] = realMaxVertices;
realMaxVertices += std::ceil(imgParams.width / step) * std::ceil(imgParams.height / step);
realMaxVertices += divideRoundUp(imgParams.width, step) *
divideRoundUp(imgParams.height, step);
}
std::vector<Point3d> verticesCoordsPrepare(realMaxVertices);
std::vector<double> pixSizePrepare(realMaxVertices);
Expand Down Expand Up @@ -1135,8 +1136,8 @@ void DelaunayGraphCut::fuseFromDepthMaps(const StaticVector<int>& cams, const Po
}
}

int syMax = std::ceil(height/step);
int sxMax = std::ceil(width/step);
int syMax = divideRoundUp(height, step);
int sxMax = divideRoundUp(width, step);
#pragma omp parallel for
for(int sy = 0; sy < syMax; ++sy)
{
Expand Down
14 changes: 14 additions & 0 deletions src/aliceVision/numeric/numeric.hpp
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Expand Up @@ -570,6 +570,20 @@ void SplitRange(const T range_start, const T range_end, const int nb_split,
}
}

template<class T>
constexpr T divideRoundUp(T x, T y)
{
static_assert(std::is_integral<T>::value, "divideRoundUp only works with integer arguments");
const auto xPos = x >= 0;
const auto yPos = y >= 0;
if (xPos == yPos) {
return x / y + T((x % y) != 0);
} else {
// negative result, rounds towards zero anyways
return x / y;
}
}

/**
* This function initializes the global state of random number generators that e.g. our tests
* depend on. This makes it possible to have exactly reproducible program runtime behavior
Expand Down
61 changes: 61 additions & 0 deletions src/aliceVision/numeric/numeric_test.cpp
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Expand Up @@ -113,3 +113,64 @@ BOOST_AUTO_TEST_CASE(Numeric_MeanAndVarianceAlongRows) {
BOOST_CHECK_SMALL(0.25-variance(0), 1e-8);
BOOST_CHECK_SMALL(1.25-variance(1), 1e-8);
}

BOOST_AUTO_TEST_CASE(Numeric_divideRoundUp)
{
BOOST_CHECK_EQUAL(divideRoundUp(0, 1), 0);
BOOST_CHECK_EQUAL(divideRoundUp(1, 1), 1);
BOOST_CHECK_EQUAL(divideRoundUp(2, 1), 2);
BOOST_CHECK_EQUAL(divideRoundUp(0, 2), 0);
BOOST_CHECK_EQUAL(divideRoundUp(1, 2), 1);
BOOST_CHECK_EQUAL(divideRoundUp(2, 2), 1);
BOOST_CHECK_EQUAL(divideRoundUp(3, 2), 2);
BOOST_CHECK_EQUAL(divideRoundUp(4, 2), 2);
BOOST_CHECK_EQUAL(divideRoundUp(999, 1000), 1);
BOOST_CHECK_EQUAL(divideRoundUp(1000, 1000), 1);
BOOST_CHECK_EQUAL(divideRoundUp(1001, 1000), 2);
BOOST_CHECK_EQUAL(divideRoundUp(1000999, 1000), 1001);
BOOST_CHECK_EQUAL(divideRoundUp(1001000, 1000), 1001);
BOOST_CHECK_EQUAL(divideRoundUp(1001001, 1000), 1002);

BOOST_CHECK_EQUAL(divideRoundUp(-1, 1), -1);
BOOST_CHECK_EQUAL(divideRoundUp(-2, 1), -2);
BOOST_CHECK_EQUAL(divideRoundUp(-0, 2), 0);
BOOST_CHECK_EQUAL(divideRoundUp(-1, 2), 0);
BOOST_CHECK_EQUAL(divideRoundUp(-2, 2), -1);
BOOST_CHECK_EQUAL(divideRoundUp(-3, 2), -1);
BOOST_CHECK_EQUAL(divideRoundUp(-4, 2), -2);
BOOST_CHECK_EQUAL(divideRoundUp(-999, 1000), 0);
BOOST_CHECK_EQUAL(divideRoundUp(-1000, 1000), -1);
BOOST_CHECK_EQUAL(divideRoundUp(-1001, 1000), -1);
BOOST_CHECK_EQUAL(divideRoundUp(-1000999, 1000), -1000);
BOOST_CHECK_EQUAL(divideRoundUp(-1001000, 1000), -1001);
BOOST_CHECK_EQUAL(divideRoundUp(-1001001, 1000), -1001);

BOOST_CHECK_EQUAL(divideRoundUp(0, -1), 0);
BOOST_CHECK_EQUAL(divideRoundUp(1, -1), -1);
BOOST_CHECK_EQUAL(divideRoundUp(2, -1), -2);
BOOST_CHECK_EQUAL(divideRoundUp(0, -2), 0);
BOOST_CHECK_EQUAL(divideRoundUp(1, -2), 0);
BOOST_CHECK_EQUAL(divideRoundUp(2, -2), -1);
BOOST_CHECK_EQUAL(divideRoundUp(3, -2), -1);
BOOST_CHECK_EQUAL(divideRoundUp(4, -2), -2);
BOOST_CHECK_EQUAL(divideRoundUp(999, -1000), 0);
BOOST_CHECK_EQUAL(divideRoundUp(1000, -1000), -1);
BOOST_CHECK_EQUAL(divideRoundUp(1001, -1000), -1);
BOOST_CHECK_EQUAL(divideRoundUp(1000999, -1000), -1000);
BOOST_CHECK_EQUAL(divideRoundUp(1001000, -1000), -1001);
BOOST_CHECK_EQUAL(divideRoundUp(1001001, -1000), -1001);

BOOST_CHECK_EQUAL(divideRoundUp(-1, -1), 1);
BOOST_CHECK_EQUAL(divideRoundUp(-2, -1), 2);
BOOST_CHECK_EQUAL(divideRoundUp(0, -2), 0);
BOOST_CHECK_EQUAL(divideRoundUp(-1, -2), 1);
BOOST_CHECK_EQUAL(divideRoundUp(-2, -2), 1);
BOOST_CHECK_EQUAL(divideRoundUp(-3, -2), 2);
BOOST_CHECK_EQUAL(divideRoundUp(-4, -2), 2);
BOOST_CHECK_EQUAL(divideRoundUp(-999, -1000), 1);
BOOST_CHECK_EQUAL(divideRoundUp(-1000, -1000), 1);
BOOST_CHECK_EQUAL(divideRoundUp(-1001, -1000), 2);
BOOST_CHECK_EQUAL(divideRoundUp(-1000999, -1000), 1001);
BOOST_CHECK_EQUAL(divideRoundUp(-1001000, -1000), 1001);
BOOST_CHECK_EQUAL(divideRoundUp(-1001001, -1000), 1002);
}