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Fix two bugs related to pseudo pext indirect lookup with search #631

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Merged
merged 1 commit into from
Oct 9, 2024
Merged

Fix two bugs related to pseudo pext indirect lookup with search #631

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2 changes: 1 addition & 1 deletion include/lookup/lookup.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,6 @@
namespace lookup {
[[nodiscard]] CONSTEVAL static auto make(compile_time auto input) {
return strategies<linear_search_lookup<4>,
pseudo_pext_lookup<true, 1>>::make(input);
pseudo_pext_lookup<true, 2>>::make(input);
}
} // namespace lookup
13 changes: 8 additions & 5 deletions include/lookup/pseudo_pext_lookup.hpp
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Expand Up @@ -122,7 +122,7 @@ constexpr auto count_duplicates(std::array<T, S> keys) -> std::size_t {
return dups;
}

/// count the length of the longest run of identical values (n log n)
/// count the length of the longest run of identical values (n)
template <typename T, std::size_t S>
constexpr auto count_longest_run(std::array<T, S> keys) -> std::size_t {
std::sort(keys.begin(), keys.end());
Expand All @@ -138,8 +138,11 @@ constexpr auto count_longest_run(std::array<T, S> keys) -> std::size_t {

if (curr_value == prev_value) {
current_run++;
} else {
longest_run = std::max(longest_run, current_run);
}

longest_run = std::max(longest_run, current_run);

if (curr_value != prev_value) {
current_run = 0;
}

Expand Down Expand Up @@ -241,15 +244,15 @@ constexpr auto calc_pseudo_pext_mask(std::array<entry<T, V>, S> const &pairs,
while (max_search_len > 1 && std::popcount(mask) > 4) {
auto try_mask = remove_cheapest_bit(mask, keys);
auto current_longest_run = count_longest_run(with_mask(try_mask, keys));
if (current_longest_run < max_search_len) {
if (current_longest_run <= max_search_len) {
mask = try_mask;
prev_longest_run = current_longest_run;
} else {
return std::make_tuple(mask, prev_longest_run);
}
}

return std::make_tuple(mask, std::size_t{});
return std::make_tuple(mask, prev_longest_run);
}

} // namespace detail
Expand Down
36 changes: 36 additions & 0 deletions test/lookup/pseudo_pext_lookup.cpp
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Expand Up @@ -98,3 +98,39 @@ TEMPLATE_TEST_CASE("lookup with scoped enum entries", "[pseudo pext lookup]",
CHECK(lookup[some_key_t::KAPPA] == 87);
CHECK(lookup[some_key_t::GAMMA] == 4);
}

TEST_CASE("pbt regression 0", "[pseudo pext lookup]") {
constexpr auto lookup = lookup::pseudo_pext_lookup<true, 2>::make(
CX_VALUE(lookup::input<std::uint16_t, std::uint16_t, 5>{
0, std::array<lookup::entry<std::uint16_t, std::uint16_t>, 5>{
lookup::entry<std::uint16_t, std::uint16_t>{1, 0},
lookup::entry<std::uint16_t, std::uint16_t>{3, 0},
lookup::entry<std::uint16_t, std::uint16_t>{11, 0},
lookup::entry<std::uint16_t, std::uint16_t>{16, 0},
lookup::entry<std::uint16_t, std::uint16_t>{0, 1}}}));

CHECK(lookup[1] == 0);
CHECK(lookup[3] == 0);
CHECK(lookup[11] == 0);
CHECK(lookup[16] == 0);
CHECK(lookup[0] == 1);
}

TEST_CASE("pbt regression 1", "[pseudo pext lookup]") {
constexpr auto lookup = lookup::pseudo_pext_lookup<true, 2>::make(
CX_VALUE(lookup::input<std::uint16_t, std::uint16_t, 6>{
0, std::array<lookup::entry<std::uint16_t, std::uint16_t>, 6>{
lookup::entry<std::uint16_t, std::uint16_t>{1, 0},
lookup::entry<std::uint16_t, std::uint16_t>{3, 0},
lookup::entry<std::uint16_t, std::uint16_t>{4, 0},
lookup::entry<std::uint16_t, std::uint16_t>{15, 0},
lookup::entry<std::uint16_t, std::uint16_t>{30, 0},
lookup::entry<std::uint16_t, std::uint16_t>{31, 1}}}));

CHECK(lookup[1] == 0);
CHECK(lookup[3] == 0);
CHECK(lookup[4] == 0);
CHECK(lookup[15] == 0);
CHECK(lookup[30] == 0);
CHECK(lookup[31] == 1);
}