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Use Ozaki et al.'s error bound and single-branch evaluation in orientation index filter. #1184

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Use Ozaki et al.'s error bound and single-branch evaluation in orientation index filter. #1184

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41 changes: 6 additions & 35 deletions include/geos/algorithm/CGAlgorithmsDD.h
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Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,7 @@

#include <geos/export.h>
#include <geos/math/DD.h>
#include <cmath>

// Forward declarations
namespace geos {
Expand Down Expand Up @@ -92,41 +93,14 @@ class GEOS_DLL CGAlgorithmsDD {
double pbx, double pby,
double pcx, double pcy)
{
/**
* A value which is safely greater than the relative round-off
* error in double-precision numbers
*/
double constexpr DP_SAFE_EPSILON = 1e-15;

double detsum;
double const detleft = (pax - pcx) * (pby - pcy);
double const detright = (pay - pcy) * (pbx - pcx);
double const det = detleft - detright;

if(detleft > 0.0) {
if(detright <= 0.0) {
return orientation(det);
}
else {
detsum = detleft + detright;
}
}
else if(detleft < 0.0) {
if(detright >= 0.0) {
return orientation(det);
}
else {
detsum = -detleft - detright;
}
}
else {
return orientation(det);
}

double const errbound = DP_SAFE_EPSILON * detsum;
if((det >= errbound) || (-det >= errbound)) {
return orientation(det);
}
// Coefficient due to https://doi.org/10.1007/s10543-015-0574-9
double const error = std::abs(detleft + detright)
* 3.3306690621773724e-16;
if (std::abs(det) >= error)
return (det > 0) - (det < 0);
return CGAlgorithmsDD::FAILURE;
};

Expand Down Expand Up @@ -188,6 +162,3 @@ class GEOS_DLL CGAlgorithmsDD {

} // namespace geos::algorithm
} // namespace geos



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