King_DuckZ/duckhandy
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Same conversion but without any lookup

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This commit is contained in:
King_DuckZ 2021-06-07 20:01:34 +02:00
parent e3140a3add
commit a68815b3cd
2 changed files with 3 additions and 11 deletions
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12
include/duckhandy/implem/int_conv.hpp
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@ -159,14 +159,6 @@ namespace dhandy {
using RetType = RevArray<I, 10, Tr>; using RetType = RevArray<I, 10, Tr>;
using Num = implem::NumberAdaptation<I, 10>; using Num = implem::NumberAdaptation<I, 10>;
//How to build this lookup: 1) write numbers 0, 10, 20..., 90
//in binary; 2) take the lowest 5 bits, div by 2 and write as
//decimal; 3) divide by 2; 4) the result is the position in the
//below array that should be filled in with the leading digit
//from the original 0-90 number
constexpr const char lookup[16] = {
0, 0, 0, 7, 4, 1, 0, 0, 8, 5, 2, 0, 0, 9, 6, 3
};
const bool was_negative = implem::is_negative<I, 10>(in); const bool was_negative = implem::is_negative<I, 10>(in);
RetType arr; RetType arr;
@ -178,7 +170,7 @@ namespace dhandy {
const auto last_two = in % 100; const auto last_two = in % 100;
const auto digit_low = in % 10; const auto digit_low = in % 10;
in = static_cast<I>(in / static_cast<I>(100)); in = static_cast<I>(in / static_cast<I>(100));
const auto digit_high = lookup[((last_two - digit_low) >> 1) & 0xF]; const auto digit_high = last_two / 10;
arr.push_front(Tr::to_digit(static_cast<int>(digit_low))); arr.push_front(Tr::to_digit(static_cast<int>(digit_low)));
arr.push_front(Tr::to_digit(static_cast<int>(digit_high))); arr.push_front(Tr::to_digit(static_cast<int>(digit_high)));
}; };
@ -187,7 +179,7 @@ namespace dhandy {
} }
else { else {
const auto digit_low = in % 10; const auto digit_low = in % 10;
const auto digit_high = lookup[((in - digit_low) >> 1) & 0xF]; const auto digit_high = (in / 10) % 10;
arr.push_front(Tr::to_digit(static_cast<int>(digit_low))); arr.push_front(Tr::to_digit(static_cast<int>(digit_low)));
arr.push_front(Tr::to_digit(static_cast<int>(digit_high))); arr.push_front(Tr::to_digit(static_cast<int>(digit_high)));
} }

2
speed_test_int_conv.cpp
View file

@ -33,7 +33,7 @@ void run_with_timing (
int main() { int main() {
using dhandy::int_conv; using dhandy::int_conv;
constexpr const std::size_t count = 50'000'000; constexpr const std::size_t count = 70'000'000;
std::vector<unsigned int> nums; std::vector<unsigned int> nums;
std::vector<std::string> strings; std::vector<std::string> strings;