libcruft-util/test/geom/sample/edge.cpp

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#include "coord/comparator.hpp"
#include "coord/iostream.hpp"
#include "geom/sample/edge.hpp"
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#include "rand/generic.hpp"
#include "tap.hpp"
#include <map>
int main ()
{
static constexpr int ITERATIONS = 1'000'000;
static const cruft::extent2i AREA { 3, 7 };
std::map<cruft::point2i, int, cruft::coord::ordering<>> counts;
auto sampler = cruft::geom::sample::edge (AREA);
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cruft::rand::general_generator gen (42);
cruft::TAP::logger tap;
for (int i = 0; i < ITERATIONS; ++i) {
auto const pos = sampler.eval (gen);
bool const x_perim = pos.x == 0 || pos.x == AREA.w;
bool const y_perim = pos.y == 0 || pos.y == AREA.h;
if (!x_perim && !y_perim) {
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tap.fail ("position {} falls outside perimeter: {}", i, pos);
return tap.status ();
}
auto const [val, success] = counts.try_emplace (pos, 0);
val->second++;
}
auto const expected_count = 2 * (AREA[0] + 1) + 2 * (AREA[1] - 1);
tap.expect_eq (
counts.size (),
std::size_t (expected_count),
"all perimeter options are covered"
);
auto const [lo,hi] = std::minmax_element (
std::begin (counts),
std::end (counts),
[] (auto const &a, auto const &b)
{
return a.second < b.second;
});
auto const abs_diff = hi->second - lo->second;
auto const rel_diff = float (abs_diff) / lo->second;
tap.expect_lt (
std::abs (rel_diff), 0.05f,
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"occurence counts are evenly spaced: {}:{} vs {}:{}",
hi->first, hi->second,
lo->first, lo->second
);
return tap.status ();
}