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161 paired block bloom bpk adjustment #163

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merged 1 commit into from
Dec 18, 2022
Merged

161 paired block bloom bpk adjustment #163

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13 changes: 7 additions & 6 deletions plugin/speedb/paired_filter/speedb_paired_bloom_internal.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -192,14 +192,14 @@ inline int GetBitPosInBlockForHash(uint32_t hash, uint32_t set_idx) {

if (set_idx == 0) {
bitpos = hash >> 23;
if (LIKELY(bitpos > 6)) {
if (LIKELY(bitpos > static_cast<int>(kInBatchIdxNumBits - 1))) {
return bitpos;
}
hash <<= 9;
} else {
constexpr uint32_t mask = 0x007FC000;
bitpos = (hash & mask) >> 14;
if (LIKELY(bitpos > 6)) {
if (LIKELY(bitpos > static_cast<int>(kInBatchIdxNumBits - 1))) {
return bitpos;
}
}
Expand All @@ -214,7 +214,8 @@ inline void BuildBlock::SetBlockBloomBits(uint32_t hash, uint32_t set_idx,
size_t hash_set_size) {
for (auto i = 0U; i < hash_set_size; ++i) {
int bitpos = GetBitPosInBlockForHash(hash, set_idx);
block_address_[bitpos >> 3] |= (char{1} << (bitpos & kInBatchIdxNumBits));
// Find the byte, and set the proper bit within that byte
block_address_[bitpos >> 3] |= (char{1} << (bitpos & 7));
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Can you please add a comment here on why 3?

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The expectation is that the code will work for any value that is <=8.
There is a comment there.
There are comments describing it (lines 41-42 of the source file) and static assertions to verify that the limit is 256 (the index must fit within a single byte, otherwise the code will break).
That is the reason for the >>3 and & 7
Per your request, I have added a comment to clarify the >> and & where they are used
Please see additional commit.

hash *= 0x9e3779b9;
}
}
Expand Down Expand Up @@ -268,7 +269,7 @@ bool ReadBlock::AreAllBlockBloomBitsSet(uint32_t hash, uint32_t set_idx,

#ifdef HAVE_AVX2
const __m256i mask_vec = _mm256_set1_epi32(0x007FC000);
const __m256i max_bitpos_vec = _mm256_set1_epi32(7);
const __m256i max_bitpos_vec = _mm256_set1_epi32(kInBatchIdxNumBits);
const __m256i fast_range_vec = _mm256_set1_epi32(KNumBitsInBlockBloom);
const __m256i num_idx_bits_vec = _mm256_set1_epi32(kInBatchIdxNumBits);

Expand Down Expand Up @@ -364,8 +365,8 @@ bool ReadBlock::AreAllBlockBloomBitsSetNonAvx2(uint32_t hash, uint32_t set_idx,
size_t hash_set_size) const {
for (auto i = 0U; i < hash_set_size; ++i) {
int bitpos = GetBitPosInBlockForHash(hash, set_idx);
if ((block_address_[bitpos >> 3] &
(char{1} << (bitpos & kInBatchIdxNumBits))) == 0) {
// Find the byte, and check the proper bit within that byte
if ((block_address_[bitpos >> 3] & (char{1} << (bitpos & 7))) == 0) {
return false;
}
hash *= 0x9e3779b9;
Expand Down
2 changes: 1 addition & 1 deletion plugin/speedb/paired_filter/speedb_paired_bloom_internal.h
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Original file line number Diff line number Diff line change
Expand Up @@ -23,7 +23,7 @@
namespace ROCKSDB_NAMESPACE {

namespace speedb_filter {
inline constexpr size_t kPairedBloomBatchSizeInBlocks = 128U;
inline constexpr size_t kPairedBloomBatchSizeInBlocks = 32U;
// Max supported BPK. Filters using higher BPK-s will use the max
inline constexpr int kMinMillibitsPerKey = 1000.0;

Expand Down