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#include <library/cpp/testing/gtest/gtest.h>
#include <library/cpp/yt/coding/interpolative.h>
#include <library/cpp/yt/coding/varint.h>
#include <algorithm>
#include <bit>
#include <numeric>
#include <random>
#include <set>
#include <vector>
namespace NYT {
namespace {
////////////////////////////////////////////////////////////////////////////////
// Truncated binary
TEST(TTruncatedBinaryTest, Exhaustive)
{
for (ui32 rangeSize = 1; rangeSize <= 2050; ++rangeSize) {
for (ui32 value = 0; value < rangeSize; ++value) {
std::vector<char> buffer(16, 0);
TBitWriter writer(buffer.data());
NInterpolativeCodingDetail::WriteTruncatedBinary(&writer, value, rangeSize);
writer.Finish();
TBitReader reader(buffer.data());
EXPECT_EQ(NInterpolativeCodingDetail::ReadTruncatedBinary(&reader, rangeSize), value)
<< "rangeSize=" << rangeSize << " value=" << value;
}
}
}
TEST(TTruncatedBinaryTest, MinimalLength)
{
// Every codeword is floor(log2(rangeSize)) or ceil(log2(rangeSize)) bits.
for (ui32 rangeSize = 1; rangeSize <= 1000; ++rangeSize) {
int lowWidth = std::bit_width(rangeSize) - 1;
for (ui32 value = 0; value < rangeSize; ++value) {
std::vector<char> buffer(16, 0);
TBitWriter writer(buffer.data());
NInterpolativeCodingDetail::WriteTruncatedBinary(&writer, value, rangeSize);
char* end = writer.Finish();
TBitReader reader(buffer.data());
NInterpolativeCodingDetail::ReadTruncatedBinary(&reader, rangeSize);
const char* readEnd = reader.Finish();
i64 bytes = end - buffer.data();
// Read must consume no more bytes than were written.
EXPECT_LE(readEnd - buffer.data(), bytes);
EXPECT_LE(bytes, (lowWidth + 1 + 7) / 8 + 1);
}
}
}
////////////////////////////////////////////////////////////////////////////////
// Interpolative coding
template <class T>
std::vector<char> Encode(const std::vector<T>& values, ui32 lo, ui32 hi)
{
std::vector<char> buffer(values.size() * sizeof(ui32) + 16, 0);
TBitWriter writer(buffer.data());
InterpolativeEncode(&writer, TRange(values), lo, hi);
char* end = writer.Finish();
buffer.resize(end - buffer.data());
return buffer;
}
template <class T>
std::vector<T> Decode(std::vector<char> buffer, int count, ui32 lo, ui32 hi)
{
buffer.resize(buffer.size() + 8, 0); // reader may over-read up to 8 bytes
std::vector<T> values(count);
TBitReader reader(buffer.data());
InterpolativeDecode(&reader, TMutableRange(values), lo, hi);
return values;
}
template <class T>
void ExpectRoundTrip(const std::vector<T>& values, ui32 lo, ui32 hi)
{
auto decoded = Decode<T>(Encode(values, lo, hi), std::ssize(values), lo, hi);
EXPECT_EQ(decoded, values);
}
TEST(TInterpolativeCodingTest, Empty)
{
ExpectRoundTrip<ui32>({}, 0, 100);
}
TEST(TInterpolativeCodingTest, Single)
{
ExpectRoundTrip<ui32>({0}, 0, 0);
ExpectRoundTrip<ui32>({42}, 0, 100);
ExpectRoundTrip<ui32>({100}, 0, 100);
}
TEST(TInterpolativeCodingTest, SmallCases)
{
ExpectRoundTrip<ui32>({3, 7}, 0, 10);
ExpectRoundTrip<ui32>({0, 1, 2}, 0, 2); // full, zero bits
ExpectRoundTrip<ui32>({0, 5, 10}, 0, 10); // boundaries present
ExpectRoundTrip<ui32>({1, 2, 3, 4, 5}, 0, 6);
}
TEST(TInterpolativeCodingTest, FullRange)
{
// Every value present => every range collapses to a singleton (zero bits).
std::vector<ui32> values(500);
std::iota(values.begin(), values.end(), 7);
auto encoded = Encode(values, 7, 506);
EXPECT_TRUE(encoded.empty());
EXPECT_EQ(Decode<ui32>(encoded, 500, 7, 506), values);
}
TEST(TInterpolativeCodingTest, RandomRoundTrip)
{
std::mt19937 rng(12345);
for (int iteration = 0; iteration < 500; ++iteration) {
ui32 universe = 1 + rng() % 200'000;
int count = std::min<ui32>(universe, 1 + rng() % 2000);
std::set<ui32> unique;
std::uniform_int_distribution<ui32> dist(0, universe - 1);
while (std::ssize(unique) < count) {
unique.insert(dist(rng));
}
std::vector<ui32> values(unique.begin(), unique.end());
ExpectRoundTrip<ui32>(values, 0, universe - 1);
}
}
TEST(TInterpolativeCodingTest, NonZeroLowerBound)
{
std::mt19937 rng(999);
for (int iteration = 0; iteration < 200; ++iteration) {
ui32 lo = rng() % 100'000;
ui32 span = 1 + rng() % 100'000;
ui32 hi = lo + span;
int count = std::min<ui32>(span + 1, 1 + rng() % 500);
std::set<ui32> unique;
std::uniform_int_distribution<ui32> dist(lo, hi);
while (std::ssize(unique) < count) {
unique.insert(dist(rng));
}
std::vector<ui32> values(unique.begin(), unique.end());
ExpectRoundTrip<ui32>(values, lo, hi);
}
}
TEST(TInterpolativeCodingTest, Ui64Values)
{
std::vector<ui64> values = {0, 1, 100, 1000, 50'000, 200'000};
ExpectRoundTrip<ui64>(values, 0, 200'000);
}
TEST(TInterpolativeCodingTest, MaxByteSize)
{
std::mt19937 rng(555);
for (int iteration = 0; iteration < 300; ++iteration) {
ui32 universe = 1 + rng() % 200'000;
int count = std::min<ui32>(universe, 1 + rng() % 1000);
std::set<ui32> unique;
std::uniform_int_distribution<ui32> dist(0, universe - 1);
while (std::ssize(unique) < count) {
unique.insert(dist(rng));
}
std::vector<ui32> values(unique.begin(), unique.end());
size_t bound = GetInterpolativeMaxByteSize(count, 0, universe - 1);
std::vector<char> buffer(bound, 0);
TBitWriter writer(buffer.data());
InterpolativeEncode(&writer, TRange(values), 0, universe - 1);
EXPECT_LE(static_cast<size_t>(writer.Finish() - buffer.data()), bound);
}
}
TEST(TInterpolativeCodingTest, MultipleListsInOneBuffer)
{
// Mirrors real usage: each list is prefixed with a varint length and is
// byte-aligned, so lists can be concatenated and read back in sequence.
std::mt19937 rng(7);
ui32 hi = 199999;
std::vector<std::vector<ui32>> lists;
for (int listIndex = 0; listIndex < 50; ++listIndex) {
int count = 1 + rng() % 300;
std::set<ui32> unique;
std::uniform_int_distribution<ui32> dist(0, hi);
while (std::ssize(unique) < count) {
unique.insert(dist(rng));
}
lists.emplace_back(unique.begin(), unique.end());
}
std::vector<char> buffer(200'000, 0);
char* ptr = buffer.data();
for (const auto& list : lists) {
ptr += WriteVarUint32(ptr, static_cast<ui32>(list.size()));
TBitWriter writer(ptr);
InterpolativeEncode(&writer, TRange(list), 0, hi);
ptr = writer.Finish();
}
const char* readPtr = buffer.data();
for (const auto& list : lists) {
ui32 count;
readPtr += ReadVarUint32(readPtr, &count);
ASSERT_EQ(count, list.size());
std::vector<ui32> decoded(count);
TBitReader reader(readPtr);
InterpolativeDecode(&reader, TMutableRange(decoded), 0, hi);
readPtr = reader.Finish();
EXPECT_EQ(decoded, list);
}
}
////////////////////////////////////////////////////////////////////////////////
} // namespace
} // namespace NYT
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