mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-10-08 17:40:49 +00:00
Performance improvement for DoubleDelta:
* inlined getDeltaWriteSpec * got rid of std::singbit()
This commit is contained in:
parent
b6372d40f0
commit
b29ed823ed
@ -26,7 +26,7 @@ extern const int CANNOT_DECOMPRESS;
|
||||
namespace
|
||||
{
|
||||
|
||||
Int64 getMaxValueForByteSize(UInt8 byte_size)
|
||||
inline Int64 getMaxValueForByteSize(Int8 byte_size)
|
||||
{
|
||||
switch (byte_size)
|
||||
{
|
||||
@ -56,6 +56,7 @@ const std::array<UInt8, 5> DELTA_SIZES{7, 9, 12, 32, 64};
|
||||
template <typename T>
|
||||
WriteSpec getDeltaWriteSpec(const T & value)
|
||||
{
|
||||
// TODO: to speed up things a bit by counting number of leading zeroes instead of doing lost of comparisons
|
||||
if (value > -63 && value < 64)
|
||||
{
|
||||
return WriteSpec{2, 0b10, 7};
|
||||
@ -107,14 +108,15 @@ UInt32 getCompressedDataSize(UInt8 data_bytes_size, UInt32 uncompressed_size)
|
||||
template <typename ValueType>
|
||||
UInt32 compressDataForType(const char * source, UInt32 source_size, char * dest)
|
||||
{
|
||||
// Since only unsinged int has granted 2-compliment overflow handling, we are doing math here on unsigned types.
|
||||
// To simplify and booletproof code, we operate enforce ValueType to be unsigned too.
|
||||
// Since only unsinged int has granted 2-compliment overflow handling,
|
||||
// we are doing math here only on unsigned types.
|
||||
// To simplify and booletproof code, we enforce ValueType to be unsigned too.
|
||||
static_assert(is_unsigned_v<ValueType>, "ValueType must be unsigned.");
|
||||
using UnsignedDeltaType = ValueType;
|
||||
|
||||
// We use signed delta type to turn huge unsigned values into smaller signed:
|
||||
// ffffffff => -1
|
||||
using SignedDeltaType = typename std::make_signed<UnsignedDeltaType>::type;
|
||||
using SignedDeltaType = typename std::make_signed_t<UnsignedDeltaType>;
|
||||
|
||||
if (source_size % sizeof(ValueType) != 0)
|
||||
throw Exception("Cannot compress, data size " + toString(source_size)
|
||||
@ -170,7 +172,8 @@ UInt32 compressDataForType(const char * source, UInt32 source_size, char * dest)
|
||||
else
|
||||
{
|
||||
const SignedDeltaType signed_dd = static_cast<SignedDeltaType>(double_delta);
|
||||
const auto sign = std::signbit(signed_dd);
|
||||
const auto sign = signed_dd < 0;
|
||||
|
||||
// -1 shirnks dd down to fit into number of bits, and there can't be 0, so it is OK.
|
||||
const auto abs_value = static_cast<UnsignedDeltaType>(std::abs(signed_dd) - 1);
|
||||
const auto write_spec = getDeltaWriteSpec(signed_dd);
|
||||
|
Loading…
Reference in New Issue
Block a user