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[base] [bits] Move NumUsedBits to bits.hpp.

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Artyom Polkovnikov 2014-11-18 16:42:19 +03:00 • committed by Alex Zolotarev
parent 5617504297
commit dee08407b4
3 changed files with 30 additions and 18 deletions
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8
base/base_tests/bits_test.cpp
View file

@ -100,3 +100,11 @@ UNIT_TEST(NumHiZeroBits64)
TEST_EQUAL(bits::NumHiZeroBits64(0x0FABCDEF0FABCDEFULL), 4, ());
TEST_EQUAL(bits::NumHiZeroBits64(0x000000000000FDEFULL), 48, ());
}
UNIT_TEST(NumUsedBits)
{
TEST_EQUAL(bits::NumUsedBits(0), 0, ());
TEST_EQUAL(bits::NumUsedBits(0xFFFFFFFFFFFFFFFFULL), 64, ());
TEST_EQUAL(bits::NumUsedBits(0x0FABCDEF0FABCDEFULL), 60, ());
TEST_EQUAL(bits::NumUsedBits(0x000000000000FDEFULL), 16, ());
}

9
base/bits.hpp
View file

@ -164,4 +164,13 @@ namespace bits
while ((n & (uint64_t(1) << 63)) == 0) { ++result; n <<= 1; }
return result;
}
// Computes number of bits needed to store the number, it is not equal to number of ones.
// E.g. if we have a number (in bit representation) 00001000b then NumUsedBits is 4.
inline uint32_t NumUsedBits(uint64_t n)
{
uint32_t result = 0;
while (n != 0) { ++result; n >>= 1; }
return result;
}
}

31
coding/compressed_bit_vector.cpp
View file

@ -5,6 +5,7 @@
#include "writer.hpp"
#include "../base/assert.hpp"
#include "../base/bits.hpp"
namespace {
void VarintEncode(vector<u8> & dst, u64 n)
@ -73,12 +74,6 @@ namespace {
return n;
}
inline u32 NumUsedBits(u64 n)
{
u32 result = 0;
while (n != 0) { ++result; n >>= 1; }
return result;
}
vector<u32> SerialFreqsToDistrTable(Reader & reader, u64 & decodeOffset, u64 cnt)
{
vector<u32> freqs;
@ -173,7 +168,7 @@ void BuildCompressedBitVector(Writer & writer, vector<u32> const & posOnes, int
CHECK_LESS(prevOnePos, posOnes[i], ());
// Accumulate size of diff encoding.
u64 diff = posOnes[i] - prevOnePos;
u32 diffBitsize = NumUsedBits(diff - 1);
u32 diffBitsize = bits::NumUsedBits(diff - 1);
numBytesDiffsEncVint += (diffBitsize + BLOCK_SIZE - 1) / BLOCK_SIZE;
numBitsDiffsEncArith += diffBitsize > 0 ? diffBitsize - 1 : 0;
++diffsSizesFreqs[diffBitsize];
@ -183,14 +178,14 @@ void BuildCompressedBitVector(Writer & writer, vector<u32> const & posOnes, int
if (onesRangeLen > 0)
{
// Accumulate size of ones-range encoding.
u32 onesRangeLenBitsize = NumUsedBits(onesRangeLen - 1);
u32 onesRangeLenBitsize = bits::NumUsedBits(onesRangeLen - 1);
numBytesRangesEncVint += (onesRangeLenBitsize + BLOCK_SIZE - 1) / BLOCK_SIZE;
numBitsRangesEncArith += onesRangeLenBitsize > 0 ? onesRangeLenBitsize - 1 : 0;
++ranges1SizesFreqs[onesRangeLenBitsize];
onesRangeLen = 0;
}
// Accumulate size of zeros-range encoding.
u32 zeros_range_len_bitsize = NumUsedBits(posOnes[i] - prevOnePos - 2);
u32 zeros_range_len_bitsize = bits::NumUsedBits(posOnes[i] - prevOnePos - 2);
numBytesRangesEncVint += (zeros_range_len_bitsize + BLOCK_SIZE - 1) / BLOCK_SIZE;
numBitsRangesEncArith += zeros_range_len_bitsize > 0 ? zeros_range_len_bitsize - 1 : 0;
++ranges0SizesFreqs[zeros_range_len_bitsize];
@ -201,7 +196,7 @@ void BuildCompressedBitVector(Writer & writer, vector<u32> const & posOnes, int
// Accumulate size of remaining ones-range encoding.
if (onesRangeLen > 0)
{
u32 onesRangeLenBitsize = NumUsedBits(onesRangeLen - 1);
u32 onesRangeLenBitsize = bits::NumUsedBits(onesRangeLen - 1);
numBytesRangesEncVint += (onesRangeLenBitsize + BLOCK_SIZE - 1) / BLOCK_SIZE;
numBitsRangesEncArith = onesRangeLenBitsize > 0 ? onesRangeLenBitsize - 1 : 0;
++ranges1SizesFreqs[onesRangeLenBitsize];
@ -312,7 +307,7 @@ void BuildCompressedBitVector(Writer & writer, vector<u32> const & posOnes, int
for (u64 i = 0; i < posOnes.size(); ++i)
{
CHECK_GREATER(posOnes[i], prevOnePos, ());
u32 bitsUsed = NumUsedBits(posOnes[i] - prevOnePos - 1);
u32 bitsUsed = bits::NumUsedBits(posOnes[i] - prevOnePos - 1);
arithEnc.Encode(bitsUsed);
++cntElements;
prevOnePos = posOnes[i];
@ -336,7 +331,7 @@ void BuildCompressedBitVector(Writer & writer, vector<u32> const & posOnes, int
CHECK_GREATER(posOnes[i], prevOnePos, ());
// Encode one's pos (diff - 1).
u64 diff = posOnes[i] - prevOnePos - 1;
u32 bitsUsed = NumUsedBits(diff);
u32 bitsUsed = bits::NumUsedBits(diff);
if (bitsUsed > 1)
{
// Most significant bit is always 1 for non-zero diffs, so don't store it.
@ -424,13 +419,13 @@ void BuildCompressedBitVector(Writer & writer, vector<u32> const & posOnes, int
if (onesRangeLen > 0)
{
// Encode ones range bits size.
u32 bitsUsed = NumUsedBits(onesRangeLen - 1);
u32 bitsUsed = bits::NumUsedBits(onesRangeLen - 1);
arith_enc1.Encode(bitsUsed);
++cntElements1;
onesRangeLen = 0;
}
// Encode zeros range bits size - 1.
u32 bitsUsed = NumUsedBits(posOnes[i] - prevOnePos - 2);
u32 bitsUsed = bits::NumUsedBits(posOnes[i] - prevOnePos - 2);
arith_enc0.Encode(bitsUsed);
++cntElements0;
}
@ -440,7 +435,7 @@ void BuildCompressedBitVector(Writer & writer, vector<u32> const & posOnes, int
if (onesRangeLen > 0)
{
// Encode last ones range size - 1.
u32 bitsUsed = NumUsedBits(onesRangeLen - 1);
u32 bitsUsed = bits::NumUsedBits(onesRangeLen - 1);
arith_enc1.Encode(bitsUsed);
++cntElements1;
onesRangeLen = 0;
@ -470,7 +465,7 @@ void BuildCompressedBitVector(Writer & writer, vector<u32> const & posOnes, int
if (onesRangeLen > 0)
{
// Encode ones range bits size.
u32 bitsUsed = NumUsedBits(onesRangeLen - 1);
u32 bitsUsed = bits::NumUsedBits(onesRangeLen - 1);
if (bitsUsed > 1)
{
// Most significant bit for non-zero values is always 1, don't encode it.
@ -480,7 +475,7 @@ void BuildCompressedBitVector(Writer & writer, vector<u32> const & posOnes, int
onesRangeLen = 0;
}
// Encode zeros range bits size - 1.
u32 bitsUsed = NumUsedBits(posOnes[i] - prevOnePos - 2);
u32 bitsUsed = bits::NumUsedBits(posOnes[i] - prevOnePos - 2);
if (bitsUsed > 1)
{
// Most significant bit for non-zero values is always 1, don't encode it.
@ -494,7 +489,7 @@ void BuildCompressedBitVector(Writer & writer, vector<u32> const & posOnes, int
if (onesRangeLen > 0)
{
// Encode last ones range size - 1.
u32 bitsUsed = NumUsedBits(onesRangeLen - 1);
u32 bitsUsed = bits::NumUsedBits(onesRangeLen - 1);
if (bitsUsed > 1)
{
// Most significant bit for non-zero values is always 1, don't encode it.