blob: f12acd19d13d0c4b71e4cb9cbcf1e77520ebd67a [file] [log] [blame]
#include "./deorummolae.h"
#include <array>
#include <cstdio>
#include "third_party/esaxx/sais.hxx"
/* Used for quick SA-entry to file mapping. Each file is padded to size that
is a multiple of chunk size. */
#define CHUNK_SIZE 64
/* Length of substring that is considered to be covered by dictionary string. */
#define CUT_MATCH 6
/* Minimal dictionary entry size. */
#define MIN_MATCH 24
/* Non tunable definitions. */
#define CHUNK_MASK (CHUNK_SIZE - 1)
#define COVERAGE_SIZE (1 << (DM_LOG_MAX_FILES - 6))
/* File coverage: every bit set to 1 denotes a file covered by an isle. */
typedef std::array<uint64_t, COVERAGE_SIZE> Coverage;
/* Symbol of text alphabet. */
typedef int32_t TextChar;
/* Pointer to position in text. */
typedef uint32_t TextIdx;
/* SAIS sarray_type; unfortunately, must be a signed type. */
typedef int32_t TextSaIdx;
static size_t popcount(uint64_t u) {
return static_cast<size_t>(__builtin_popcountll(u));
}
/* Condense terminators and pad file entries. */
static void rewriteText(std::vector<TextChar>* text) {
TextChar terminator = text->back();
TextChar prev = terminator;
TextIdx to = 0;
for (TextIdx from = 0; from < text->size(); ++from) {
TextChar next = text->at(from);
if (next < 256 || prev < 256) {
text->at(to++) = next;
if (next >= 256) terminator = next;
}
prev = next;
}
text->resize(to);
if (text->empty()) text->push_back(terminator);
while (text->size() & CHUNK_MASK) text->push_back(terminator);
}
/* Reenumerate terminators for smaller alphabet. */
static void remapTerminators(std::vector<TextChar>* text,
TextChar* next_terminator) {
TextChar prev = -1;
TextChar x = 256;
for (TextIdx i = 0; i < text->size(); ++i) {
TextChar next = text->at(i);
if (next < 256) { // Char.
// Do nothing.
} else if (prev < 256) { // Terminator after char.
next = x++;
} else { // Terminator after terminator.
next = prev;
}
text->at(i) = next;
prev = next;
}
*next_terminator = x;
}
/* Combine all file entries; create mapping position->file. */
static void buildFullText(std::vector<std::vector<TextChar>>* data,
std::vector<TextChar>* full_text, std::vector<TextIdx>* file_map,
std::vector<TextIdx>* file_offset, TextChar* next_terminator) {
file_map->resize(0);
file_offset->resize(0);
full_text->resize(0);
for (TextIdx i = 0; i < data->size(); ++i) {
file_offset->push_back(full_text->size());
std::vector<TextChar>& file = data->at(i);
rewriteText(&file);
full_text->insert(full_text->end(), file.begin(), file.end());
file_map->insert(file_map->end(), file.size() / CHUNK_SIZE, i);
}
if (false) remapTerminators(full_text, next_terminator);
}
/* Build longest-common-prefix based on suffix array and text.
TODO: borrowed -> unknown efficiency. */
static void buildLcp(std::vector<TextChar>* text, std::vector<TextIdx>* sa,
std::vector<TextIdx>* lcp, std::vector<TextIdx>* invese_sa) {
TextIdx size = static_cast<TextIdx>(text->size());
lcp->resize(size);
TextIdx k = 0;
lcp->at(size - 1) = 0;
for (TextIdx i = 0; i < size; ++i) {
if (invese_sa->at(i) == size - 1) {
k = 0;
continue;
}
// Suffix which follow i-th suffix.
TextIdx j = sa->at(invese_sa->at(i) + 1);
while (i + k < size && j + k < size && text->at(i + k) == text->at(j + k)) {
++k;
}
lcp->at(invese_sa->at(i)) = k;
if (k > 0) --k;
}
}
/* Isle is a range in SA with LCP not less than some value.
When we raise the LCP requirement, the isle sunks and smaller isles appear
instead. */
typedef struct {
TextIdx lcp;
TextIdx l;
TextIdx r;
Coverage coverage;
} Isle;
/* Helper routine for `cutMatch`. */
static void poisonData(TextIdx pos, TextIdx length,
std::vector<std::vector<TextChar>>* data, std::vector<TextIdx>* file_map,
std::vector<TextIdx>* file_offset, TextChar* next_terminator) {
TextIdx f = file_map->at(pos / CHUNK_SIZE);
pos -= file_offset->at(f);
std::vector<TextChar>& file = data->at(f);
TextIdx l = (length == CUT_MATCH) ? CUT_MATCH : 1;
for (TextIdx j = 0; j < l; j++, pos++) {
if (file[pos] >= 256) continue;
if (file[pos + 1] >= 256) {
file[pos] = file[pos + 1];
} else if (pos > 0 && file[pos - 1] >= 256) {
file[pos] = file[pos - 1];
} else {
file[pos] = (*next_terminator)++;
}
}
}
/* Remove substrings of a given match from files.
Substrings are replaced with unique terminators, so next iteration SA would
not allow to cross removed areas. */
static void cutMatch(std::vector<std::vector<TextChar>>* data, TextIdx index,
TextIdx length, std::vector<TextIdx>* sa, std::vector<TextIdx>* lcp,
std::vector<TextIdx>* invese_sa, TextChar* next_terminator,
std::vector<TextIdx>* file_map, std::vector<TextIdx>* file_offset) {
while (length >= CUT_MATCH) {
TextIdx i = index;
while (lcp->at(i) >= length) {
i++;
poisonData(
sa->at(i), length, data, file_map, file_offset, next_terminator);
}
while (true) {
poisonData(
sa->at(index), length, data, file_map, file_offset, next_terminator);
if (index == 0 || lcp->at(index - 1) < length) break;
index--;
}
length--;
index = invese_sa->at(sa->at(index) + 1);
}
}
std::string DM_generate(size_t dictionary_size_limit,
const std::vector<size_t>& sample_sizes, const uint8_t* sample_data) {
{
TextIdx tmp = static_cast<TextIdx>(dictionary_size_limit);
if ((tmp != dictionary_size_limit) || (tmp > 1u << 30)) {
fprintf(stderr, "dictionary_size_limit is too large\n");
return "";
}
}
/* Could use 256 + '0' for easier debugging. */
TextChar next_terminator = 256;
std::string output;
std::vector<std::vector<TextChar>> data;
TextIdx offset = 0;
size_t num_samples = sample_sizes.size();
if (num_samples > DM_MAX_FILES) num_samples = DM_MAX_FILES;
for (size_t n = 0; n < num_samples; ++n) {
TextIdx delta = static_cast<TextIdx>(sample_sizes[n]);
if (delta != sample_sizes[n]) {
fprintf(stderr, "sample is too large\n");
return "";
}
if (delta == 0) {
fprintf(stderr, "0-length samples are prohibited\n");
return "";
}
TextIdx next_offset = offset + delta;
if (next_offset <= offset) {
fprintf(stderr, "corpus is too large\n");
return "";
}
data.push_back(
std::vector<TextChar>(sample_data + offset, sample_data + next_offset));
offset = next_offset;
data.back().push_back(next_terminator++);
}
/* Most arrays are allocated once, and then just resized to smaller and
smaller sizes. */
std::vector<TextChar> full_text;
std::vector<TextIdx> file_map;
std::vector<TextIdx> file_offset;
std::vector<TextIdx> sa;
std::vector<TextIdx> invese_sa;
std::vector<TextIdx> lcp;
std::vector<Isle> isles;
std::vector<char> output_data;
TextIdx total = 0;
TextIdx total_cost = 0;
TextIdx best_cost;
Isle best_isle;
size_t min_count = num_samples;
while (true) {
TextIdx max_match = static_cast<TextIdx>(dictionary_size_limit) - total;
buildFullText(&data, &full_text, &file_map, &file_offset, &next_terminator);
sa.resize(full_text.size());
/* Hopefully, non-negative TextSaIdx is the same sa TextIdx counterpart. */
saisxx(full_text.data(), reinterpret_cast<TextSaIdx*>(sa.data()),
static_cast<TextChar>(full_text.size()), next_terminator);
invese_sa.resize(full_text.size());
for (TextIdx i = 0; i < full_text.size(); ++i) {
invese_sa[sa[i]] = i;
}
buildLcp(&full_text, &sa, &lcp, &invese_sa);
/* Do not rebuild SA/LCP, just use different selection. */
retry:
best_cost = 0;
best_isle = {0, 0, 0, {{0}}};
isles.resize(0);
isles.push_back(best_isle);
for (TextIdx i = 0; i < lcp.size(); ++i) {
TextIdx l = i;
Coverage cov = {{0}};
size_t f = file_map[sa[i] / CHUNK_SIZE];
cov[f >> 6] = (static_cast<uint64_t>(1)) << (f & 63);
while (lcp[i] < isles.back().lcp) {
Isle& top = isles.back();
top.r = i;
l = top.l;
for (size_t x = 0; x < cov.size(); ++x) cov[x] |= top.coverage[x];
size_t count = 0;
for (size_t x = 0; x < cov.size(); ++x) count += popcount(cov[x]);
TextIdx effective_lcp = top.lcp;
/* Restrict (last) dictionary entry length. */
if (effective_lcp > max_match) effective_lcp = max_match;
TextIdx cost = count * effective_lcp;
if (cost > best_cost && count >= min_count &&
effective_lcp >= MIN_MATCH) {
best_cost = cost;
best_isle = top;
best_isle.lcp = effective_lcp;
}
isles.pop_back();
for (size_t x = 0; x < cov.size(); ++x) {
isles.back().coverage[x] |= cov[x];
}
}
if (lcp[i] > isles.back().lcp) isles.push_back({lcp[i], l, 0, {{0}}});
for (size_t x = 0; x < cov.size(); ++x) {
isles.back().coverage[x] |= cov[x];
}
}
/* When saturated matches do not match length restrictions, lower the
saturation requirements. */
if (best_cost == 0 || best_isle.lcp < MIN_MATCH) {
if (min_count >= 8) {
min_count = (min_count * 7) / 8;
fprintf(stderr, "Retry: min_count=%zu\n", min_count);
goto retry;
}
break;
}
/* Save the entry. */
fprintf(stderr, "Savings: %d+%d, dictionary: %d+%d\n",
total_cost, best_cost, total, best_isle.lcp);
int* piece = &full_text[sa[best_isle.l]];
output.insert(output.end(), piece, piece + best_isle.lcp);
total += best_isle.lcp;
total_cost += best_cost;
cutMatch(&data, best_isle.l, best_isle.lcp, &sa, &lcp, &invese_sa,
&next_terminator, &file_map, &file_offset);
if (total >= dictionary_size_limit) break;
}
return output;
}