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| </pre><pre class="rust"><code><span class="kw">use </span><span class="kw">super</span>::bitpacker::BitPacker; |
| <span class="kw">use </span><span class="kw">super</span>::compute_num_bits; |
| <span class="kw">use crate</span>::{minmax, BitUnpacker}; |
| |
| <span class="kw">const </span>BLOCK_SIZE: usize = <span class="number">128</span>; |
| |
| <span class="doccomment">/// `BlockedBitpacker` compresses data in blocks of |
| /// 128 elements, while keeping an index on it |
| </span><span class="attribute">#[derive(Debug, Clone)] |
| </span><span class="kw">pub struct </span>BlockedBitpacker { |
| <span class="comment">// bitpacked blocks |
| </span>compressed_blocks: Vec<u8>, |
| <span class="comment">// uncompressed data, collected until BLOCK_SIZE |
| </span>buffer: Vec<u64>, |
| offset_and_bits: Vec<BlockedBitpackerEntryMetaData>, |
| } |
| <span class="kw">impl </span>Default <span class="kw">for </span>BlockedBitpacker { |
| <span class="kw">fn </span>default() -> <span class="self">Self </span>{ |
| BlockedBitpacker::new() |
| } |
| } |
| |
| <span class="doccomment">/// `BlockedBitpackerEntryMetaData` encodes the |
| /// offset and bit_width into a u64 bit field |
| /// |
| /// This saves some space, since 7byte is more |
| /// than enough and also keeps the access fast |
| /// because of alignment |
| </span><span class="attribute">#[derive(Debug, Clone, Default)] |
| </span><span class="kw">struct </span>BlockedBitpackerEntryMetaData { |
| encoded: u64, |
| base_value: u64, |
| } |
| |
| <span class="kw">impl </span>BlockedBitpackerEntryMetaData { |
| <span class="kw">fn </span>new(offset: u64, num_bits: u8, base_value: u64) -> <span class="self">Self </span>{ |
| <span class="kw">let </span>encoded = offset | (num_bits <span class="kw">as </span>u64) << (<span class="number">64 </span>- <span class="number">8</span>); |
| <span class="self">Self </span>{ |
| encoded, |
| base_value, |
| } |
| } |
| <span class="kw">fn </span>offset(<span class="kw-2">&</span><span class="self">self</span>) -> u64 { |
| (<span class="self">self</span>.encoded << <span class="number">8</span>) >> <span class="number">8 |
| </span>} |
| <span class="kw">fn </span>num_bits(<span class="kw-2">&</span><span class="self">self</span>) -> u8 { |
| (<span class="self">self</span>.encoded >> <span class="number">56</span>) <span class="kw">as </span>u8 |
| } |
| <span class="kw">fn </span>base_value(<span class="kw-2">&</span><span class="self">self</span>) -> u64 { |
| <span class="self">self</span>.base_value |
| } |
| } |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>metadata_test() { |
| <span class="kw">let </span>meta = BlockedBitpackerEntryMetaData::new(<span class="number">50000</span>, <span class="number">6</span>, <span class="number">40000</span>); |
| <span class="macro">assert_eq!</span>(meta.offset(), <span class="number">50000</span>); |
| <span class="macro">assert_eq!</span>(meta.num_bits(), <span class="number">6</span>); |
| } |
| |
| <span class="kw">fn </span>mem_usage<T>(items: <span class="kw-2">&</span>Vec<T>) -> usize { |
| items.capacity() * std::mem::size_of::<T>() |
| } |
| |
| <span class="kw">impl </span>BlockedBitpacker { |
| <span class="kw">pub fn </span>new() -> <span class="self">Self </span>{ |
| <span class="kw">let </span><span class="kw-2">mut </span>compressed_blocks = <span class="macro">vec!</span>[]; |
| compressed_blocks.resize(<span class="number">8</span>, <span class="number">0</span>); |
| <span class="self">Self </span>{ |
| compressed_blocks, |
| buffer: <span class="macro">vec!</span>[], |
| offset_and_bits: <span class="macro">vec!</span>[], |
| } |
| } |
| |
| <span class="doccomment">/// The memory used (inclusive childs) |
| </span><span class="kw">pub fn </span>mem_usage(<span class="kw-2">&</span><span class="self">self</span>) -> usize { |
| std::mem::size_of::<BlockedBitpacker>() |
| + <span class="self">self</span>.compressed_blocks.capacity() |
| + mem_usage(<span class="kw-2">&</span><span class="self">self</span>.offset_and_bits) |
| + mem_usage(<span class="kw-2">&</span><span class="self">self</span>.buffer) |
| } |
| |
| <span class="attribute">#[inline] |
| </span><span class="kw">pub fn </span>add(<span class="kw-2">&mut </span><span class="self">self</span>, val: u64) { |
| <span class="self">self</span>.buffer.push(val); |
| <span class="kw">if </span><span class="self">self</span>.buffer.len() == BLOCK_SIZE <span class="kw">as </span>usize { |
| <span class="self">self</span>.flush(); |
| } |
| } |
| |
| <span class="kw">pub fn </span>flush(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="kw">if let </span><span class="prelude-val">Some</span>((min_value, max_value)) = minmax(<span class="self">self</span>.buffer.iter()) { |
| <span class="kw">let </span><span class="kw-2">mut </span>bit_packer = BitPacker::new(); |
| <span class="kw">let </span>num_bits_block = compute_num_bits(<span class="kw-2">*</span>max_value - min_value); |
| <span class="comment">// todo performance: the padding handling could be done better, e.g. use a slice and |
| // return num_bytes written from bitpacker |
| </span><span class="self">self</span>.compressed_blocks |
| .resize(<span class="self">self</span>.compressed_blocks.len() - <span class="number">8</span>, <span class="number">0</span>); <span class="comment">// remove padding for bitpacker |
| </span><span class="kw">let </span>offset = <span class="self">self</span>.compressed_blocks.len() <span class="kw">as </span>u64; |
| <span class="comment">// todo performance: for some bit_width we |
| // can encode multiple vals into the |
| // mini_buffer before checking to flush |
| // (to be done in BitPacker) |
| </span><span class="kw">for </span>val <span class="kw">in </span><span class="self">self</span>.buffer.iter() { |
| bit_packer |
| .write( |
| <span class="kw-2">*</span>val - min_value, |
| num_bits_block, |
| <span class="kw-2">&mut </span><span class="self">self</span>.compressed_blocks, |
| ) |
| .expect(<span class="string">"cannot write bitpacking to output"</span>); <span class="comment">// write to in memory can't fail |
| </span>} |
| bit_packer.flush(<span class="kw-2">&mut </span><span class="self">self</span>.compressed_blocks).unwrap(); |
| <span class="self">self</span>.offset_and_bits |
| .push(BlockedBitpackerEntryMetaData::new( |
| offset, |
| num_bits_block, |
| <span class="kw-2">*</span>min_value, |
| )); |
| |
| <span class="self">self</span>.buffer.clear(); |
| <span class="self">self</span>.compressed_blocks |
| .resize(<span class="self">self</span>.compressed_blocks.len() + <span class="number">8</span>, <span class="number">0</span>); <span class="comment">// add padding for bitpacker |
| </span>} |
| } |
| <span class="attribute">#[inline] |
| </span><span class="kw">pub fn </span>get(<span class="kw-2">&</span><span class="self">self</span>, idx: usize) -> u64 { |
| <span class="kw">let </span>metadata_pos = idx / BLOCK_SIZE <span class="kw">as </span>usize; |
| <span class="kw">let </span>pos_in_block = idx % BLOCK_SIZE <span class="kw">as </span>usize; |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(metadata) = <span class="self">self</span>.offset_and_bits.get(metadata_pos) { |
| <span class="kw">let </span>unpacked = BitUnpacker::new(metadata.num_bits()).get( |
| pos_in_block <span class="kw">as </span>u32, |
| <span class="kw-2">&</span><span class="self">self</span>.compressed_blocks[metadata.offset() <span class="kw">as </span>usize..], |
| ); |
| unpacked + metadata.base_value() |
| } <span class="kw">else </span>{ |
| <span class="self">self</span>.buffer[pos_in_block] |
| } |
| } |
| |
| <span class="kw">pub fn </span>iter(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="kw">impl </span>Iterator<Item = u64> + <span class="lifetime">'_ </span>{ |
| <span class="comment">// todo performance: we could decompress a whole block and cache it instead |
| </span><span class="kw">let </span>bitpacked_elems = <span class="self">self</span>.offset_and_bits.len() * BLOCK_SIZE; |
| <span class="kw">let </span>iter = (<span class="number">0</span>..bitpacked_elems) |
| .map(<span class="kw">move </span>|idx| <span class="self">self</span>.get(idx)) |
| .chain(<span class="self">self</span>.buffer.iter().cloned()); |
| iter |
| } |
| } |
| |
| <span class="attribute">#[cfg(test)] |
| </span><span class="kw">mod </span>tests { |
| <span class="kw">use super</span>::<span class="kw-2">*</span>; |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>blocked_bitpacker_empty() { |
| <span class="kw">let </span>blocked_bitpacker = BlockedBitpacker::new(); |
| <span class="macro">assert_eq!</span>(blocked_bitpacker.iter().collect::<Vec<u64>>(), <span class="macro">vec!</span>[]); |
| } |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>blocked_bitpacker_one() { |
| <span class="kw">let </span><span class="kw-2">mut </span>blocked_bitpacker = BlockedBitpacker::new(); |
| blocked_bitpacker.add(<span class="number">50000</span>); |
| <span class="macro">assert_eq!</span>(blocked_bitpacker.get(<span class="number">0</span>), <span class="number">50000</span>); |
| <span class="macro">assert_eq!</span>(blocked_bitpacker.iter().collect::<Vec<u64>>(), <span class="macro">vec!</span>[<span class="number">50000</span>]); |
| } |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>blocked_bitpacker_test() { |
| <span class="kw">let </span><span class="kw-2">mut </span>blocked_bitpacker = BlockedBitpacker::new(); |
| <span class="kw">for </span>val <span class="kw">in </span><span class="number">0</span>..<span class="number">21500 </span>{ |
| blocked_bitpacker.add(val); |
| } |
| <span class="kw">for </span>val <span class="kw">in </span><span class="number">0</span>..<span class="number">21500 </span>{ |
| <span class="macro">assert_eq!</span>(blocked_bitpacker.get(val <span class="kw">as </span>usize), val); |
| } |
| <span class="macro">assert_eq!</span>(blocked_bitpacker.iter().count(), <span class="number">21500</span>); |
| <span class="macro">assert_eq!</span>(blocked_bitpacker.iter().last().unwrap(), <span class="number">21499</span>); |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../" data-current-crate="tantivy_bitpacker" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
