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[formulas] Some optimizations in area geographic formula

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This commit is contained in:
Vissarion Fisikopoulos 2021-02-04 21:13:01 +02:00
parent 336f3968cb
commit baf414ae02
3 changed files with 23 additions and 20 deletions
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34
include/boost/geometry/formulas/area_formulas.hpp
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@ -172,7 +172,6 @@ public:
static inline void evaluate_coeffs_n(CT const& n, CT coeffs_n[])
{
switch (SeriesOrder) {
case 0:
coeffs_n[0] = CT(2)/CT(3);
@ -446,13 +445,19 @@ public:
std::size_t const series_order_plus_two = SeriesOrder + 2;
// Basic trigonometric computations
// the compiler could optimize here using sincos function
// TODO: optimization: those quantities are already computed in inverse formula
// at least in some inverse formulas, so do not compute them again here
CT sin_bet1 = sin(lat1r);
CT cos_bet1 = cos(lat1r);
CT sin_bet2 = sin(lat2r);
CT cos_bet2 = cos(lat2r);
sin_bet1 *= one_minus_f;
sin_bet2 *= one_minus_f;
normalize(sin_bet1, cos_bet1);
normalize(sin_bet2, cos_bet2);
CT const tan_bet1 = tan(lat1r) * one_minus_f;
CT const tan_bet2 = tan(lat2r) * one_minus_f;
CT const cos_bet1 = cos(atan(tan_bet1));
CT const cos_bet2 = cos(atan(tan_bet2));
CT const sin_bet1 = tan_bet1 * cos_bet1;
CT const sin_bet2 = tan_bet2 * cos_bet2;
CT const sin_alp1 = sin(alp1);
CT const cos_alp1 = cos(alp1);
CT const cos_alp2 = cos(alp2);
@ -460,18 +465,12 @@ public:
// Spherical term computation
//CT const sin_omg1 = sin_alp0 * sin_bet1;
//CT const cos_omg1 = cos_alp1 * cos_bet1;
//CT const sin_omg2 = sin_alp0 * sin_bet2;
//CT const cos_omg2 = cos_alp2 * cos_bet2;
//CT cos_omg12 = cos_omg1 * cos_omg2 + sin_omg1 * sin_omg2;
CT excess;
bool meridian = get<0>(p2) - get<0>(p1) == CT(0)
|| get<1>(p1) == CT(90) || get<1>(p1) == -CT(90)
|| get<1>(p2) == CT(90) || get<1>(p2) == -CT(90);
//std::cout << cos_omg12 << " " << std::abs(sin_bet2 - sin_bet1) << std::endl;
auto const half_pi = math::pi<CT>() / 2;
bool meridian = lon2r - lon1r == CT(0)
|| lat1r == half_pi || lat1r == -half_pi
|| lat2r == half_pi || lat2r == -half_pi;
if (!meridian && i_res.distance < 10000) // short segment
{
@ -504,6 +503,7 @@ public:
// Ellipsoidal term computation (uses integral approximation)
CT const cos_alp0 = math::sqrt(CT(1) - math::sqr(sin_alp0));
//CT const cos_alp0 = hypot(cos_alp1, sin_alp1 * sin_bet1);
CT cos_sig1 = cos_alp1 * cos_bet1;
CT cos_sig2 = cos_alp2 * cos_bet2;
CT sin_sig1 = sin_bet1;

5
include/boost/geometry/strategy/geographic/area.hpp
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@ -179,7 +179,10 @@ public :
PointOfSegment const& p2,
state<Geometry>& st) const
{
if (! geometry::math::equals(get<0>(p1), get<0>(p2)))
// if the segment in not on a meridian or equator
if (! geometry::math::equals(get<0>(p1), get<0>(p2))
&& ! (geometry::math::equals(get<1>(p1), 0)
&& geometry::math::equals(get<1>(p2), 0)))
{
// Area formula is implemented for a maximum series order 5
constexpr auto SeriesOrderNorm = SeriesOrder > 5 ? 5 : SeriesOrder;

4
test/algorithms/area/area_geo.cpp
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@ -127,7 +127,7 @@ void test_geo_strategies()
BOOST_CHECK_CLOSE(area_most_accurate, area_less_accurate, .001);
BOOST_CHECK_CLOSE(area_most_accurate, area_default, .001);
/*
// timings and accuracy
std::cout.precision(25);
std::size_t exp_times = 100000;
@ -191,7 +191,7 @@ void test_geo_strategies()
for (int j=0; j < exp_times; j++) area = bg::area(geometry_geo, geographic_vincenty5);
std::cout << double( clock() - startTime ) / (double)CLOCKS_PER_SEC<< " ";
std::cout << area << std::endl;}
*/
}
int test_main(int, char* [])