-#include "vp4.h"
+#include "db.h"
+#include "turbopfor-encode.h"
#include <algorithm>
-#include <arpa/inet.h>
#include <assert.h>
#include <chrono>
-#include <endian.h>
-#include <fcntl.h>
+#include <iosfwd>
+#include <math.h>
+#include <memory>
+#include <stdint.h>
#include <stdio.h>
+#include <stdlib.h>
#include <string.h>
#include <string>
-#include <sys/mman.h>
+#include <string_view>
#include <sys/stat.h>
-#include <sys/types.h>
-#include <unistd.h>
-#include <unordered_map>
+#include <utility>
#include <vector>
#include <zstd.h>
#define dprintf(...)
//#define dprintf(...) fprintf(stderr, __VA_ARGS__);
+#define NUM_TRIGRAMS 16777216
+
using namespace std;
using namespace std::chrono;
string zstd_compress(const string &src, string *tempbuf);
+constexpr unsigned num_overflow_slots = 16;
+
static inline uint32_t read_unigram(const string_view s, size_t idx)
{
if (idx < s.size()) {
class PostingListBuilder {
public:
- void add_docid(uint32_t docid);
+ inline void add_docid(uint32_t docid);
void finish();
string encoded;
void write_header(uint32_t docid);
void append_block();
- vector<uint32_t> pending_docids;
+ vector<uint32_t> pending_deltas;
- uint32_t last_block_end;
+ uint32_t last_block_end, last_docid = -1;
};
void PostingListBuilder::add_docid(uint32_t docid)
{
// Deduplicate against the last inserted value, if any.
- if (pending_docids.empty()) {
- if (encoded.empty()) {
- // Very first docid.
- write_header(docid);
- ++num_docids;
- last_block_end = docid;
- return;
- } else if (docid == last_block_end) {
- return;
- }
- } else {
- if (docid == pending_docids.back()) {
- return;
- }
+ if (docid == last_docid) {
+ return;
+ }
+
+ if (num_docids == 0) {
+ // Very first docid.
+ write_header(docid);
+ ++num_docids;
+ last_block_end = last_docid = docid;
+ return;
}
- pending_docids.push_back(docid);
- if (pending_docids.size() == 128) {
+ pending_deltas.push_back(docid - last_docid - 1);
+ last_docid = docid;
+ if (pending_deltas.size() == 128) {
append_block();
- pending_docids.clear();
+ pending_deltas.clear();
last_block_end = docid;
}
++num_docids;
void PostingListBuilder::finish()
{
- if (pending_docids.empty()) {
+ if (pending_deltas.empty()) {
return;
}
// No interleaving for partial blocks.
unsigned char buf[P4NENC_BOUND(128)];
- unsigned char *end = p4d1enc32(pending_docids.data(), pending_docids.size(), buf, last_block_end);
+ unsigned char *end = encode_pfor_single_block<128>(pending_deltas.data(), pending_deltas.size(), /*interleaved=*/false, buf);
encoded.append(reinterpret_cast<char *>(buf), reinterpret_cast<char *>(end));
}
void PostingListBuilder::append_block()
{
unsigned char buf[P4NENC_BOUND(128)];
- assert(pending_docids.size() == 128);
- unsigned char *end = p4d1enc128v32(pending_docids.data(), 128, buf, last_block_end);
+ assert(pending_deltas.size() == 128);
+ unsigned char *end = encode_pfor_single_block<128>(pending_deltas.data(), 128, /*interleaved=*/true, buf);
encoded.append(reinterpret_cast<char *>(buf), reinterpret_cast<char *>(end));
}
void PostingListBuilder::write_header(uint32_t docid)
{
unsigned char buf[P4NENC_BOUND(1)];
- size_t bytes = p4nd1enc128v32(&docid, 1, buf);
- encoded.append(reinterpret_cast<char *>(buf), bytes);
+ unsigned char *end = write_baseval(docid, buf);
+ encoded.append(reinterpret_cast<char *>(buf), end - buf);
}
class Corpus {
public:
- Corpus(size_t block_size)
- : block_size(block_size) {}
+ Corpus(FILE *outfp, size_t block_size)
+ : invindex(new PostingListBuilder *[NUM_TRIGRAMS]), outfp(outfp), block_size(block_size)
+ {
+ fill(invindex.get(), invindex.get() + NUM_TRIGRAMS, nullptr);
+ }
+ ~Corpus()
+ {
+ for (unsigned i = 0; i < NUM_TRIGRAMS; ++i) {
+ delete invindex[i];
+ }
+ }
+
void add_file(string filename);
void flush_block();
- vector<string> filename_blocks;
- unordered_map<uint32_t, PostingListBuilder> invindex;
+ vector<uint64_t> filename_blocks;
size_t num_files = 0, num_files_in_block = 0, num_blocks = 0;
+ bool seen_trigram(uint32_t trgm)
+ {
+ return invindex[trgm] != nullptr;
+ }
+ PostingListBuilder &get_pl_builder(uint32_t trgm)
+ {
+ if (invindex[trgm] == nullptr) {
+ invindex[trgm] = new PostingListBuilder;
+ }
+ return *invindex[trgm];
+ }
private:
+ unique_ptr<PostingListBuilder *[]> invindex;
+ FILE *outfp;
string current_block;
string tempbuf;
const size_t block_size;
if (s.size() >= 3) {
for (size_t j = 0; j < s.size() - 2; ++j) {
uint32_t trgm = read_trigram(s, j);
- invindex[trgm].add_docid(docid);
+ get_pl_builder(trgm).add_docid(docid);
}
}
ptr += s.size() + 1;
}
// Compress and add the filename block.
- filename_blocks.push_back(zstd_compress(current_block, &tempbuf));
+ filename_blocks.push_back(ftell(outfp));
+ string compressed = zstd_compress(current_block, &tempbuf);
+ if (fwrite(compressed.data(), compressed.size(), 1, outfp) != 1) {
+ perror("fwrite()");
+ exit(1);
+ }
current_block.clear();
num_files_in_block = 0;
++num_blocks;
}
-const char *handle_directory(const char *ptr, Corpus *corpus)
+string read_cstr(FILE *fp)
+{
+ string ret;
+ for (;;) {
+ int ch = getc(fp);
+ if (ch == -1) {
+ perror("getc");
+ exit(1);
+ }
+ if (ch == 0) {
+ return ret;
+ }
+ ret.push_back(ch);
+ }
+}
+
+void handle_directory(FILE *fp, Corpus *corpus)
{
- ptr += sizeof(db_directory);
+ db_directory dummy;
+ if (fread(&dummy, sizeof(dummy), 1, fp) != 1) {
+ if (feof(fp)) {
+ return;
+ } else {
+ perror("fread");
+ }
+ }
- string dir_path = ptr;
- ptr += dir_path.size() + 1;
+ string dir_path = read_cstr(fp);
if (dir_path == "/") {
dir_path = "";
}
for (;;) {
- uint8_t type = *ptr++;
+ int type = getc(fp);
if (type == DBE_NORMAL) {
- string filename = ptr;
+ string filename = read_cstr(fp);
corpus->add_file(dir_path + "/" + filename);
- ptr += filename.size() + 1;
} else if (type == DBE_DIRECTORY) {
- string dirname = ptr;
+ string dirname = read_cstr(fp);
corpus->add_file(dir_path + "/" + dirname);
- ptr += dirname.size() + 1;
} else {
- return ptr;
+ return; // Probably end.
}
}
}
void read_mlocate(const char *filename, Corpus *corpus)
{
- int fd = open(filename, O_RDONLY);
- if (fd == -1) {
+ FILE *fp = fopen(filename, "rb");
+ if (fp == nullptr) {
perror(filename);
exit(1);
}
- off_t len = lseek(fd, 0, SEEK_END);
- if (len == -1) {
- perror("lseek");
- exit(1);
- }
- const char *data = (char *)mmap(nullptr, len, PROT_READ, MAP_SHARED, fd, /*offset=*/0);
- if (data == MAP_FAILED) {
- perror("mmap");
+
+ db_header hdr;
+ if (fread(&hdr, sizeof(hdr), 1, fp) != 1) {
+ perror("short read");
exit(1);
}
- const db_header *hdr = (const db_header *)data;
-
// TODO: Care about the base path.
- string path = data + sizeof(db_header);
- uint64_t offset = sizeof(db_header) + path.size() + 1 + ntohl(hdr->conf_size);
-
- const char *ptr = data + offset;
- while (ptr < data + len) {
- ptr = handle_directory(ptr, corpus);
+ string path = read_cstr(fp);
+ while (!feof(fp)) {
+ handle_directory(fp, corpus);
}
-
- munmap((void *)data, len);
- close(fd);
+ fclose(fp);
}
string zstd_compress(const string &src, string *tempbuf)
return string(tempbuf->data(), size);
}
+bool is_prime(uint32_t x)
+{
+ if ((x % 2) == 0 || (x % 3) == 0) {
+ return false;
+ }
+ uint32_t limit = ceil(sqrt(x));
+ for (uint32_t factor = 5; factor <= limit; ++factor) {
+ if ((x % factor) == 0) {
+ return false;
+ }
+ }
+ return true;
+}
+
+uint32_t next_prime(uint32_t x)
+{
+ if ((x % 2) == 0) {
+ ++x;
+ }
+ while (!is_prime(x)) {
+ x += 2;
+ }
+ return x;
+}
+
+unique_ptr<Trigram[]> create_hashtable(Corpus &corpus, const vector<uint32_t> &all_trigrams, uint32_t ht_size, uint32_t num_overflow_slots)
+{
+ unique_ptr<Trigram[]> ht(new Trigram[ht_size + num_overflow_slots + 1]); // 1 for the sentinel element at the end.
+ for (unsigned i = 0; i < ht_size + num_overflow_slots + 1; ++i) {
+ ht[i].trgm = uint32_t(-1);
+ ht[i].num_docids = 0;
+ ht[i].offset = 0;
+ }
+ for (uint32_t trgm : all_trigrams) {
+ // We don't know offset yet, so set it to zero.
+ Trigram to_insert{ trgm, uint32_t(corpus.get_pl_builder(trgm).num_docids), 0 };
+
+ uint32_t bucket = hash_trigram(trgm, ht_size);
+ unsigned distance = 0;
+ while (ht[bucket].num_docids != 0) {
+ // Robin Hood hashing; reduces the longest distance by a lot.
+ unsigned other_distance = bucket - hash_trigram(ht[bucket].trgm, ht_size);
+ if (distance > other_distance) {
+ swap(to_insert, ht[bucket]);
+ distance = other_distance;
+ }
+
+ ++bucket, ++distance;
+ if (distance > num_overflow_slots) {
+ return nullptr;
+ }
+ }
+ ht[bucket] = to_insert;
+ }
+ return ht;
+}
+
void do_build(const char *infile, const char *outfile, int block_size)
{
steady_clock::time_point start __attribute__((unused)) = steady_clock::now();
- Corpus corpus(block_size);
+ umask(0027);
+ FILE *outfp = fopen(outfile, "wb");
+
+ // Write the header.
+ Header hdr;
+ memcpy(hdr.magic, "\0plocate", 8);
+ hdr.version = -1; // Mark as broken.
+ hdr.hashtable_size = 0; // Not known yet.
+ hdr.extra_ht_slots = num_overflow_slots;
+ hdr.num_docids = 0;
+ hdr.hash_table_offset_bytes = -1; // We don't know these offsets yet.
+ hdr.filename_index_offset_bytes = -1;
+ fwrite(&hdr, sizeof(hdr), 1, outfp);
+
+ Corpus corpus(outfp, block_size);
read_mlocate(infile, &corpus);
if (false) { // To read a plain text file.
}
corpus.flush_block();
dprintf("Read %zu files from %s\n", corpus.num_files, infile);
+ hdr.num_docids = corpus.filename_blocks.size();
+ // Stick an empty block at the end as sentinel.
+ corpus.filename_blocks.push_back(ftell(outfp));
+ const size_t bytes_for_filenames = corpus.filename_blocks.back() - corpus.filename_blocks.front();
+
+ // Write the offsets to the filenames.
+ hdr.filename_index_offset_bytes = ftell(outfp);
+ const size_t bytes_for_filename_index = corpus.filename_blocks.size() * sizeof(uint64_t);
+ fwrite(corpus.filename_blocks.data(), corpus.filename_blocks.size(), sizeof(uint64_t), outfp);
+ corpus.filename_blocks.clear();
+ corpus.filename_blocks.shrink_to_fit();
+
+ // Finish up encoding the posting lists.
size_t trigrams = 0, longest_posting_list = 0;
- size_t bytes_used = 0;
- for (auto &[trigram, pl_builder] : corpus.invindex) {
+ size_t bytes_for_posting_lists = 0;
+ for (unsigned trgm = 0; trgm < NUM_TRIGRAMS; ++trgm) {
+ if (!corpus.seen_trigram(trgm))
+ continue;
+ PostingListBuilder &pl_builder = corpus.get_pl_builder(trgm);
pl_builder.finish();
longest_posting_list = max(longest_posting_list, pl_builder.num_docids);
trigrams += pl_builder.num_docids;
- bytes_used += pl_builder.encoded.size();
+ bytes_for_posting_lists += pl_builder.encoded.size();
}
dprintf("%zu files, %zu different trigrams, %zu entries, avg len %.2f, longest %zu\n",
corpus.num_files, corpus.invindex.size(), trigrams, double(trigrams) / corpus.invindex.size(), longest_posting_list);
- dprintf("%zu bytes used for posting lists (%.2f bits/entry)\n", bytes_used, 8 * bytes_used / double(trigrams));
+ dprintf("%zu bytes used for posting lists (%.2f bits/entry)\n", bytes_for_posting_lists, 8 * bytes_for_posting_lists / double(trigrams));
dprintf("Building posting lists took %.1f ms.\n\n", 1e3 * duration<float>(steady_clock::now() - start).count());
+ // Find the used trigrams.
vector<uint32_t> all_trigrams;
- for (auto &[trigram, pl_builder] : corpus.invindex) {
- all_trigrams.push_back(trigram);
+ for (unsigned trgm = 0; trgm < NUM_TRIGRAMS; ++trgm) {
+ if (corpus.seen_trigram(trgm)) {
+ all_trigrams.push_back(trgm);
+ }
}
- sort(all_trigrams.begin(), all_trigrams.end());
- umask(0027);
- FILE *outfp = fopen(outfile, "wb");
+ // Create the hash table.
+ unique_ptr<Trigram[]> hashtable;
+ uint32_t ht_size = next_prime(all_trigrams.size());
+ for (;;) {
+ hashtable = create_hashtable(corpus, all_trigrams, ht_size, num_overflow_slots);
+ if (hashtable == nullptr) {
+ dprintf("Failed creating hash table of size %u, increasing by 5%% and trying again.\n", ht_size);
+ ht_size = next_prime(ht_size * 1.05);
+ } else {
+ dprintf("Created hash table of size %u.\n\n", ht_size);
+ break;
+ }
+ }
- // Write the header.
- uint64_t num_trigrams = corpus.invindex.size(); // 64 to get alignment.
- fwrite(&num_trigrams, sizeof(num_trigrams), 1, outfp);
+ // Find the offsets for each posting list.
+ size_t bytes_for_hashtable = (ht_size + num_overflow_slots + 1) * sizeof(Trigram);
+ uint64_t offset = ftell(outfp) + bytes_for_hashtable;
+ for (unsigned i = 0; i < ht_size + num_overflow_slots + 1; ++i) {
+ hashtable[i].offset = offset; // Needs to be there even for empty slots.
+ if (hashtable[i].num_docids == 0) {
+ continue;
+ }
- // Find out where the posting lists will end.
- uint64_t offset = sizeof(uint64_t) * 2 + 16 * all_trigrams.size();
- uint64_t filename_index_offset = offset;
- for (auto &[trigram, pl_builder] : corpus.invindex) {
- filename_index_offset += pl_builder.encoded.size();
+ const string &encoded = corpus.get_pl_builder(hashtable[i].trgm).encoded;
+ offset += encoded.size();
}
- fwrite(&filename_index_offset, sizeof(filename_index_offset), 1, outfp);
- size_t bytes_for_trigrams = 0, bytes_for_posting_lists = 0, bytes_for_filename_index = 0, bytes_for_filenames = 0;
- for (uint32_t trgm : all_trigrams) {
- // 16 bytes: trgm (4), number of docids (4), byte offset (8)
- fwrite(&trgm, sizeof(trgm), 1, outfp); // One byte wasted, but OK.
- const PostingListBuilder &pl_builder = corpus.invindex[trgm];
- uint32_t num_docids = pl_builder.num_docids;
- fwrite(&num_docids, sizeof(num_docids), 1, outfp);
- fwrite(&offset, sizeof(offset), 1, outfp);
- offset += pl_builder.encoded.size();
- bytes_for_trigrams += 16;
- }
+ // Write the hash table.
+ hdr.hash_table_offset_bytes = ftell(outfp);
+ hdr.hashtable_size = ht_size;
+ fwrite(hashtable.get(), ht_size + num_overflow_slots + 1, sizeof(Trigram), outfp);
// Write the actual posting lists.
- for (uint32_t trgm : all_trigrams) {
- const string &encoded = corpus.invindex[trgm].encoded;
+ for (unsigned i = 0; i < ht_size + num_overflow_slots + 1; ++i) {
+ if (hashtable[i].num_docids == 0) {
+ continue;
+ }
+ const string &encoded = corpus.get_pl_builder(hashtable[i].trgm).encoded;
fwrite(encoded.data(), encoded.size(), 1, outfp);
- bytes_for_posting_lists += encoded.size();
- }
-
- // Stick an empty block at the end as sentinel.
- corpus.filename_blocks.push_back("");
-
- // Write the offsets to the filenames.
- offset = filename_index_offset + corpus.filename_blocks.size() * sizeof(offset);
- for (const string &filename : corpus.filename_blocks) {
- fwrite(&offset, sizeof(offset), 1, outfp);
- offset += filename.size();
- bytes_for_filename_index += sizeof(offset);
- bytes_for_filenames += filename.size();
- }
-
- // Write the actual filenames.
- for (const string &filename : corpus.filename_blocks) {
- fwrite(filename.data(), filename.size(), 1, outfp);
}
+ // Rewind, and write the updated header.
+ hdr.version = 0;
+ fseek(outfp, 0, SEEK_SET);
+ fwrite(&hdr, sizeof(hdr), 1, outfp);
fclose(outfp);
- size_t total_bytes __attribute__((unused)) = (bytes_for_trigrams + bytes_for_posting_lists + bytes_for_filename_index + bytes_for_filenames);
+ size_t total_bytes __attribute__((unused)) = (bytes_for_hashtable + bytes_for_posting_lists + bytes_for_filename_index + bytes_for_filenames);
dprintf("Block size: %7d files\n", block_size);
- dprintf("Trigrams: %'7.1f MB\n", bytes_for_trigrams / 1048576.0);
+ dprintf("Hash table: %'7.1f MB\n", bytes_for_hashtable / 1048576.0);
dprintf("Posting lists: %'7.1f MB\n", bytes_for_posting_lists / 1048576.0);
dprintf("Filename index: %'7.1f MB\n", bytes_for_filename_index / 1048576.0);
dprintf("Filenames: %'7.1f MB\n", bytes_for_filenames / 1048576.0);
projects / plocate / blobdiff