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zstd/lib/dictBuilder/cover.c
Nick Terrell 71c5263c00 Attribute cover dictionary code
2017-02-07 11:35:07 -08:00

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/**
* Copyright (c) 2016-present, Yann Collet, Facebook, Inc.
* All rights reserved.
*
* This source code is licensed under the BSD-style license found in the
* LICENSE file in the root directory of this source tree. An additional grant
* of patent rights can be found in the PATENTS file in the same directory.
*/
/* *****************************************************************************
* Constructs a dictionary using a heuristic based on the following paper:
*
* Liao, Petri, Moffat, Wirth
* Effective Construction of Relative Lempel-Ziv Dictionaries
* Published in WWW 2016.
*
* Adapted from code originally written by @ot (Giuseppe Ottaviano).
******************************************************************************/
/*-*************************************
* Dependencies
***************************************/
#include <stdio.h> /* fprintf */
#include <stdlib.h> /* malloc, free, qsort */
#include <string.h> /* memset */
#include <time.h> /* clock */
#include "mem.h" /* read */
#include "pool.h"
#include "threading.h"
#include "zstd_internal.h" /* includes zstd.h */
#ifndef ZDICT_STATIC_LINKING_ONLY
#define ZDICT_STATIC_LINKING_ONLY
#endif
#include "zdict.h"
/*-*************************************
* Constants
***************************************/
#define COVER_MAX_SAMPLES_SIZE (sizeof(size_t) == 8 ? ((U32)-1) : ((U32)1 GB))
/*-*************************************
* Console display
***************************************/
static int g_displayLevel = 2;
#define DISPLAY(...) \
{ \
fprintf(stderr, __VA_ARGS__); \
fflush(stderr); \
}
#define LOCALDISPLAYLEVEL(displayLevel, l, ...) \
if (displayLevel >= l) { \
DISPLAY(__VA_ARGS__); \
} /* 0 : no display; 1: errors; 2: default; 3: details; 4: debug */
#define DISPLAYLEVEL(l, ...) LOCALDISPLAYLEVEL(g_displayLevel, l, __VA_ARGS__)
#define LOCALDISPLAYUPDATE(displayLevel, l, ...) \
if (displayLevel >= l) { \
if ((clock() - g_time > refreshRate) || (displayLevel >= 4)) { \
g_time = clock(); \
DISPLAY(__VA_ARGS__); \
if (displayLevel >= 4) \
fflush(stdout); \
} \
}
#define DISPLAYUPDATE(l, ...) LOCALDISPLAYUPDATE(g_displayLevel, l, __VA_ARGS__)
static const clock_t refreshRate = CLOCKS_PER_SEC * 15 / 100;
static clock_t g_time = 0;
/*-*************************************
* Hash table
***************************************
* A small specialized hash map for storing activeDmers.
* The map does not resize, so if it becomes full it will loop forever.
* Thus, the map must be large enough to store every value.
* The map implements linear probing and keeps its load less than 0.5.
*/
#define MAP_EMPTY_VALUE ((U32)-1)
typedef struct COVER_map_pair_t_s {
U32 key;
U32 value;
} COVER_map_pair_t;
typedef struct COVER_map_s {
COVER_map_pair_t *data;
U32 sizeLog;
U32 size;
U32 sizeMask;
} COVER_map_t;
/**
* Clear the map.
*/
static void COVER_map_clear(COVER_map_t *map) {
memset(map->data, MAP_EMPTY_VALUE, map->size * sizeof(COVER_map_pair_t));
}
/**
* Initializes a map of the given size.
* Returns 1 on success and 0 on failure.
* The map must be destroyed with COVER_map_destroy().
* The map is only guaranteed to be large enough to hold size elements.
*/
static int COVER_map_init(COVER_map_t *map, U32 size) {
map->sizeLog = ZSTD_highbit32(size) + 2;
map->size = (U32)1 << map->sizeLog;
map->sizeMask = map->size - 1;
map->data = (COVER_map_pair_t *)malloc(map->size * sizeof(COVER_map_pair_t));
if (!map->data) {
map->sizeLog = 0;
map->size = 0;
return 0;
}
COVER_map_clear(map);
return 1;
}
/**
* Internal hash function
*/
static const U32 prime4bytes = 2654435761U;
static U32 COVER_map_hash(COVER_map_t *map, U32 key) {
return (key * prime4bytes) >> (32 - map->sizeLog);
}
/**
* Helper function that returns the index that a key should be placed into.
*/
static U32 COVER_map_index(COVER_map_t *map, U32 key) {
const U32 hash = COVER_map_hash(map, key);
U32 i;
for (i = hash;; i = (i + 1) & map->sizeMask) {
COVER_map_pair_t *pos = &map->data[i];
if (pos->value == MAP_EMPTY_VALUE) {
return i;
}
if (pos->key == key) {
return i;
}
}
}
/**
* Returns the pointer to the value for key.
* If key is not in the map, it is inserted and the value is set to 0.
* The map must not be full.
*/
static U32 *COVER_map_at(COVER_map_t *map, U32 key) {
COVER_map_pair_t *pos = &map->data[COVER_map_index(map, key)];
if (pos->value == MAP_EMPTY_VALUE) {
pos->key = key;
pos->value = 0;
}
return &pos->value;
}
/**
* Deletes key from the map if present.
*/
static void COVER_map_remove(COVER_map_t *map, U32 key) {
U32 i = COVER_map_index(map, key);
COVER_map_pair_t *del = &map->data[i];
U32 shift = 1;
if (del->value == MAP_EMPTY_VALUE) {
return;
}
for (i = (i + 1) & map->sizeMask;; i = (i + 1) & map->sizeMask) {
COVER_map_pair_t *const pos = &map->data[i];
/* If the position is empty we are done */
if (pos->value == MAP_EMPTY_VALUE) {
del->value = MAP_EMPTY_VALUE;
return;
}
/* If pos can be moved to del do so */
if (((i - COVER_map_hash(map, pos->key)) & map->sizeMask) >= shift) {
del->key = pos->key;
del->value = pos->value;
del = pos;
shift = 1;
} else {
++shift;
}
}
}
/**
* Destroyes a map that is inited with COVER_map_init().
*/
static void COVER_map_destroy(COVER_map_t *map) {
if (map->data) {
free(map->data);
}
map->data = NULL;
map->size = 0;
}
/*-*************************************
* Context
***************************************/
typedef struct {
const BYTE *samples;
size_t *offsets;
const size_t *samplesSizes;
size_t nbSamples;
U32 *suffix;
size_t suffixSize;
U32 *freqs;
U32 *dmerAt;
unsigned d;
} COVER_ctx_t;
/* We need a global context for qsort... */
static COVER_ctx_t *g_ctx = NULL;
/*-*************************************
* Helper functions
***************************************/
/**
* Returns the sum of the sample sizes.
*/
static size_t COVER_sum(const size_t *samplesSizes, unsigned nbSamples) {
size_t sum = 0;
size_t i;
for (i = 0; i < nbSamples; ++i) {
sum += samplesSizes[i];
}
return sum;
}
/**
* Returns -1 if the dmer at lp is less than the dmer at rp.
* Return 0 if the dmers at lp and rp are equal.
* Returns 1 if the dmer at lp is greater than the dmer at rp.
*/
static int COVER_cmp(COVER_ctx_t *ctx, const void *lp, const void *rp) {
const U32 lhs = *(const U32 *)lp;
const U32 rhs = *(const U32 *)rp;
return memcmp(ctx->samples + lhs, ctx->samples + rhs, ctx->d);
}
/**
* Same as COVER_cmp() except ties are broken by pointer value
* NOTE: g_ctx must be set to call this function. A global is required because
* qsort doesn't take an opaque pointer.
*/
static int COVER_strict_cmp(const void *lp, const void *rp) {
int result = COVER_cmp(g_ctx, lp, rp);
if (result == 0) {
result = lp < rp ? -1 : 1;
}
return result;
}
/**
* Returns the first pointer in [first, last) whose element does not compare
* less than value. If no such element exists it returns last.
*/
static const size_t *COVER_lower_bound(const size_t *first, const size_t *last,
size_t value) {
size_t count = last - first;
while (count != 0) {
size_t step = count / 2;
const size_t *ptr = first;
ptr += step;
if (*ptr < value) {
first = ++ptr;
count -= step + 1;
} else {
count = step;
}
}
return first;
}
/**
* Generic groupBy function.
* Groups an array sorted by cmp into groups with equivalent values.
* Calls grp for each group.
*/
static void
COVER_groupBy(const void *data, size_t count, size_t size, COVER_ctx_t *ctx,
int (*cmp)(COVER_ctx_t *, const void *, const void *),
void (*grp)(COVER_ctx_t *, const void *, const void *)) {
const BYTE *ptr = (const BYTE *)data;
size_t num = 0;
while (num < count) {
const BYTE *grpEnd = ptr + size;
++num;
while (num < count && cmp(ctx, ptr, grpEnd) == 0) {
grpEnd += size;
++num;
}
grp(ctx, ptr, grpEnd);
ptr = grpEnd;
}
}
/*-*************************************
* Cover functions
***************************************/
/**
* Called on each group of positions with the same dmer.
* Counts the frequency of each dmer and saves it in the suffix array.
* Fills `ctx->dmerAt`.
*/
static void COVER_group(COVER_ctx_t *ctx, const void *group,
const void *groupEnd) {
/* The group consists of all the positions with the same first d bytes. */
const U32 *grpPtr = (const U32 *)group;
const U32 *grpEnd = (const U32 *)groupEnd;
/* The dmerId is how we will reference this dmer.
* This allows us to map the whole dmer space to a much smaller space, the
* size of the suffix array.
*/
const U32 dmerId = (U32)(grpPtr - ctx->suffix);
/* Count the number of samples this dmer shows up in */
U32 freq = 0;
/* Details */
const size_t *curOffsetPtr = ctx->offsets;
const size_t *offsetsEnd = ctx->offsets + ctx->nbSamples;
/* Once *grpPtr >= curSampleEnd this occurrence of the dmer is in a
* different sample than the last.
*/
size_t curSampleEnd = ctx->offsets[0];
for (; grpPtr != grpEnd; ++grpPtr) {
/* Save the dmerId for this position so we can get back to it. */
ctx->dmerAt[*grpPtr] = dmerId;
/* Dictionaries only help for the first reference to the dmer.
* After that zstd can reference the match from the previous reference.
* So only count each dmer once for each sample it is in.
*/
if (*grpPtr < curSampleEnd) {
continue;
}
freq += 1;
/* Binary search to find the end of the sample *grpPtr is in.
* In the common case that grpPtr + 1 == grpEnd we can skip the binary
* search because the loop is over.
*/
if (grpPtr + 1 != grpEnd) {
const size_t *sampleEndPtr =
COVER_lower_bound(curOffsetPtr, offsetsEnd, *grpPtr);
curSampleEnd = *sampleEndPtr;
curOffsetPtr = sampleEndPtr + 1;
}
}
/* At this point we are never going to look at this segment of the suffix
* array again. We take advantage of this fact to save memory.
* We store the frequency of the dmer in the first position of the group,
* which is dmerId.
*/
ctx->suffix[dmerId] = freq;
}
/**
* A segment is a range in the source as well as the score of the segment.
*/
typedef struct {
U32 begin;
U32 end;
double score;
} COVER_segment_t;
/**
* Selects the best segment in an epoch.
* Segments of are scored according to the function:
*
* Let F(d) be the frequency of dmer d.
* Let S_i be the dmer at position i of segment S which has length k.
*
* Score(S) = F(S_1) + F(S_2) + ... + F(S_{k-d+1})
*
* Once the dmer d is in the dictionay we set F(d) = 0.
*/
static COVER_segment_t COVER_selectSegment(const COVER_ctx_t *ctx, U32 *freqs,
COVER_map_t *activeDmers, U32 begin,
U32 end, COVER_params_t parameters) {
/* Constants */
const U32 k = parameters.k;
const U32 d = parameters.d;
const U32 dmersInK = k - d + 1;
/* Try each segment (activeSegment) and save the best (bestSegment) */
COVER_segment_t bestSegment = {0, 0, 0};
COVER_segment_t activeSegment;
/* Reset the activeDmers in the segment */
COVER_map_clear(activeDmers);
/* The activeSegment starts at the beginning of the epoch. */
activeSegment.begin = begin;
activeSegment.end = begin;
activeSegment.score = 0;
/* Slide the activeSegment through the whole epoch.
* Save the best segment in bestSegment.
*/
while (activeSegment.end < end) {
/* The dmerId for the dmer at the next position */
U32 newDmer = ctx->dmerAt[activeSegment.end];
/* The entry in activeDmers for this dmerId */
U32 *newDmerOcc = COVER_map_at(activeDmers, newDmer);
/* If the dmer isn't already present in the segment add its score. */
if (*newDmerOcc == 0) {
/* The paper suggest using the L-0.5 norm, but experiments show that it
* doesn't help.
*/
activeSegment.score += freqs[newDmer];
}
/* Add the dmer to the segment */
activeSegment.end += 1;
*newDmerOcc += 1;
/* If the window is now too large, drop the first position */
if (activeSegment.end - activeSegment.begin == dmersInK + 1) {
U32 delDmer = ctx->dmerAt[activeSegment.begin];
U32 *delDmerOcc = COVER_map_at(activeDmers, delDmer);
activeSegment.begin += 1;
*delDmerOcc -= 1;
/* If this is the last occurence of the dmer, subtract its score */
if (*delDmerOcc == 0) {
COVER_map_remove(activeDmers, delDmer);
activeSegment.score -= freqs[delDmer];
}
}
/* If this segment is the best so far save it */
if (activeSegment.score > bestSegment.score) {
bestSegment = activeSegment;
}
}
{
/* Trim off the zero frequency head and tail from the segment. */
U32 newBegin = bestSegment.end;
U32 newEnd = bestSegment.begin;
U32 pos;
for (pos = bestSegment.begin; pos != bestSegment.end; ++pos) {
U32 freq = freqs[ctx->dmerAt[pos]];
if (freq != 0) {
newBegin = MIN(newBegin, pos);
newEnd = pos + 1;
}
}
bestSegment.begin = newBegin;
bestSegment.end = newEnd;
}
{
/* Zero out the frequency of each dmer covered by the chosen segment. */
U32 pos;
for (pos = bestSegment.begin; pos != bestSegment.end; ++pos) {
freqs[ctx->dmerAt[pos]] = 0;
}
}
return bestSegment;
}
/**
* Check the validity of the parameters.
* Returns non-zero if the parameters are valid and 0 otherwise.
*/
static int COVER_checkParameters(COVER_params_t parameters) {
/* k and d are required parameters */
if (parameters.d == 0 || parameters.k == 0) {
return 0;
}
/* d <= k */
if (parameters.d > parameters.k) {
return 0;
}
return 1;
}
/**
* Clean up a context initialized with `COVER_ctx_init()`.
*/
static void COVER_ctx_destroy(COVER_ctx_t *ctx) {
if (!ctx) {
return;
}
if (ctx->suffix) {
free(ctx->suffix);
ctx->suffix = NULL;
}
if (ctx->freqs) {
free(ctx->freqs);
ctx->freqs = NULL;
}
if (ctx->dmerAt) {
free(ctx->dmerAt);
ctx->dmerAt = NULL;
}
if (ctx->offsets) {
free(ctx->offsets);
ctx->offsets = NULL;
}
}
/**
* Prepare a context for dictionary building.
* The context is only dependent on the parameter `d` and can used multiple
* times.
* Returns 1 on success or zero on error.
* The context must be destroyed with `COVER_ctx_destroy()`.
*/
static int COVER_ctx_init(COVER_ctx_t *ctx, const void *samplesBuffer,
const size_t *samplesSizes, unsigned nbSamples,
unsigned d) {
const BYTE *const samples = (const BYTE *)samplesBuffer;
const size_t totalSamplesSize = COVER_sum(samplesSizes, nbSamples);
/* Checks */
if (totalSamplesSize < d ||
totalSamplesSize >= (size_t)COVER_MAX_SAMPLES_SIZE) {
DISPLAYLEVEL(1, "Total samples size is too large, maximum size is %u MB\n",
(COVER_MAX_SAMPLES_SIZE >> 20));
return 0;
}
/* Zero the context */
memset(ctx, 0, sizeof(*ctx));
DISPLAYLEVEL(2, "Training on %u samples of total size %u\n", nbSamples,
(U32)totalSamplesSize);
ctx->samples = samples;
ctx->samplesSizes = samplesSizes;
ctx->nbSamples = nbSamples;
/* Partial suffix array */
ctx->suffixSize = totalSamplesSize - d + 1;
ctx->suffix = (U32 *)malloc(ctx->suffixSize * sizeof(U32));
/* Maps index to the dmerID */
ctx->dmerAt = (U32 *)malloc(ctx->suffixSize * sizeof(U32));
/* The offsets of each file */
ctx->offsets = (size_t *)malloc((nbSamples + 1) * sizeof(size_t));
if (!ctx->suffix || !ctx->dmerAt || !ctx->offsets) {
DISPLAYLEVEL(1, "Failed to allocate scratch buffers\n");
COVER_ctx_destroy(ctx);
return 0;
}
ctx->freqs = NULL;
ctx->d = d;
/* Fill offsets from the samlesSizes */
{
U32 i;
ctx->offsets[0] = 0;
for (i = 1; i <= nbSamples; ++i) {
ctx->offsets[i] = ctx->offsets[i - 1] + samplesSizes[i - 1];
}
}
DISPLAYLEVEL(2, "Constructing partial suffix array\n");
{
/* suffix is a partial suffix array.
* It only sorts suffixes by their first parameters.d bytes.
* The sort is stable, so each dmer group is sorted by position in input.
*/
U32 i;
for (i = 0; i < ctx->suffixSize; ++i) {
ctx->suffix[i] = i;
}
/* qsort doesn't take an opaque pointer, so pass as a global */
g_ctx = ctx;
qsort(ctx->suffix, ctx->suffixSize, sizeof(U32), &COVER_strict_cmp);
}
DISPLAYLEVEL(2, "Computing frequencies\n");
/* For each dmer group (group of positions with the same first d bytes):
* 1. For each position we set dmerAt[position] = dmerID. The dmerID is
* (groupBeginPtr - suffix). This allows us to go from position to
* dmerID so we can look up values in freq.
* 2. We calculate how many samples the dmer occurs in and save it in
* freqs[dmerId].
*/
COVER_groupBy(ctx->suffix, ctx->suffixSize, sizeof(U32), ctx, &COVER_cmp,
&COVER_group);
ctx->freqs = ctx->suffix;
ctx->suffix = NULL;
return 1;
}
/**
* Given the prepared context build the dictionary.
*/
static size_t COVER_buildDictionary(const COVER_ctx_t *ctx, U32 *freqs,
COVER_map_t *activeDmers, void *dictBuffer,
size_t dictBufferCapacity,
COVER_params_t parameters) {
BYTE *const dict = (BYTE *)dictBuffer;
size_t tail = dictBufferCapacity;
/* Divide the data up into epochs of equal size.
* We will select at least one segment from each epoch.
*/
const U32 epochs = (U32)(dictBufferCapacity / parameters.k);
const U32 epochSize = (U32)(ctx->suffixSize / epochs);
size_t epoch;
DISPLAYLEVEL(2, "Breaking content into %u epochs of size %u\n", epochs,
epochSize);
/* Loop through the epochs until there are no more segments or the dictionary
* is full.
*/
for (epoch = 0; tail > 0; epoch = (epoch + 1) % epochs) {
const U32 epochBegin = (U32)(epoch * epochSize);
const U32 epochEnd = epochBegin + epochSize;
size_t segmentSize;
/* Select a segment */
COVER_segment_t segment = COVER_selectSegment(
ctx, freqs, activeDmers, epochBegin, epochEnd, parameters);
/* Trim the segment if necessary and if it is empty then we are done */
segmentSize = MIN(segment.end - segment.begin + parameters.d - 1, tail);
if (segmentSize == 0) {
break;
}
/* We fill the dictionary from the back to allow the best segments to be
* referenced with the smallest offsets.
*/
tail -= segmentSize;
memcpy(dict + tail, ctx->samples + segment.begin, segmentSize);
DISPLAYUPDATE(
2, "\r%u%% ",
(U32)(((dictBufferCapacity - tail) * 100) / dictBufferCapacity));
}
DISPLAYLEVEL(2, "\r%79s\r", "");
return tail;
}
/**
* Translate from COVER_params_t to ZDICT_params_t required for finalizing the
* dictionary.
*/
static ZDICT_params_t COVER_translateParams(COVER_params_t parameters) {
ZDICT_params_t zdictParams;
memset(&zdictParams, 0, sizeof(zdictParams));
zdictParams.notificationLevel = 1;
zdictParams.dictID = parameters.dictID;
zdictParams.compressionLevel = parameters.compressionLevel;
return zdictParams;
}
ZDICTLIB_API size_t COVER_trainFromBuffer(
void *dictBuffer, size_t dictBufferCapacity, const void *samplesBuffer,
const size_t *samplesSizes, unsigned nbSamples, COVER_params_t parameters) {
BYTE *const dict = (BYTE *)dictBuffer;
COVER_ctx_t ctx;
COVER_map_t activeDmers;
/* Checks */
if (!COVER_checkParameters(parameters)) {
DISPLAYLEVEL(1, "Cover parameters incorrect\n");
return ERROR(GENERIC);
}
if (nbSamples == 0) {
DISPLAYLEVEL(1, "Cover must have at least one input file\n");
return ERROR(GENERIC);
}
if (dictBufferCapacity < ZDICT_DICTSIZE_MIN) {
DISPLAYLEVEL(1, "dictBufferCapacity must be at least %u\n",
ZDICT_DICTSIZE_MIN);
return ERROR(dstSize_tooSmall);
}
/* Initialize global data */
g_displayLevel = parameters.notificationLevel;
/* Initialize context and activeDmers */
if (!COVER_ctx_init(&ctx, samplesBuffer, samplesSizes, nbSamples,
parameters.d)) {
return ERROR(GENERIC);
}
if (!COVER_map_init(&activeDmers, parameters.k - parameters.d + 1)) {
DISPLAYLEVEL(1, "Failed to allocate dmer map: out of memory\n");
COVER_ctx_destroy(&ctx);
return ERROR(GENERIC);
}
DISPLAYLEVEL(2, "Building dictionary\n");
{
const size_t tail =
COVER_buildDictionary(&ctx, ctx.freqs, &activeDmers, dictBuffer,
dictBufferCapacity, parameters);
ZDICT_params_t zdictParams = COVER_translateParams(parameters);
const size_t dictionarySize = ZDICT_finalizeDictionary(
dict, dictBufferCapacity, dict + tail, dictBufferCapacity - tail,
samplesBuffer, samplesSizes, nbSamples, zdictParams);
if (!ZSTD_isError(dictionarySize)) {
DISPLAYLEVEL(2, "Constructed dictionary of size %u\n",
(U32)dictionarySize);
}
COVER_ctx_destroy(&ctx);
COVER_map_destroy(&activeDmers);
return dictionarySize;
}
}
/**
* COVER_best_t is used for two purposes:
* 1. Synchronizing threads.
* 2. Saving the best parameters and dictionary.
*
* All of the methods except COVER_best_init() are thread safe if zstd is
* compiled with multithreaded support.
*/
typedef struct COVER_best_s {
pthread_mutex_t mutex;
pthread_cond_t cond;
size_t liveJobs;
void *dict;
size_t dictSize;
COVER_params_t parameters;
size_t compressedSize;
} COVER_best_t;
/**
* Initialize the `COVER_best_t`.
*/
static void COVER_best_init(COVER_best_t *best) {
if (!best) {
return;
}
pthread_mutex_init(&best->mutex, NULL);
pthread_cond_init(&best->cond, NULL);
best->liveJobs = 0;
best->dict = NULL;
best->dictSize = 0;
best->compressedSize = (size_t)-1;
memset(&best->parameters, 0, sizeof(best->parameters));
}
/**
* Wait until liveJobs == 0.
*/
static void COVER_best_wait(COVER_best_t *best) {
if (!best) {
return;
}
pthread_mutex_lock(&best->mutex);
while (best->liveJobs != 0) {
pthread_cond_wait(&best->cond, &best->mutex);
}
pthread_mutex_unlock(&best->mutex);
}
/**
* Call COVER_best_wait() and then destroy the COVER_best_t.
*/
static void COVER_best_destroy(COVER_best_t *best) {
if (!best) {
return;
}
COVER_best_wait(best);
if (best->dict) {
free(best->dict);
}
pthread_mutex_destroy(&best->mutex);
pthread_cond_destroy(&best->cond);
}
/**
* Called when a thread is about to be launched.
* Increments liveJobs.
*/
static void COVER_best_start(COVER_best_t *best) {
if (!best) {
return;
}
pthread_mutex_lock(&best->mutex);
++best->liveJobs;
pthread_mutex_unlock(&best->mutex);
}
/**
* Called when a thread finishes executing, both on error or success.
* Decrements liveJobs and signals any waiting threads if liveJobs == 0.
* If this dictionary is the best so far save it and its parameters.
*/
static void COVER_best_finish(COVER_best_t *best, size_t compressedSize,
COVER_params_t parameters, void *dict,
size_t dictSize) {
if (!best) {
return;
}
{
size_t liveJobs;
pthread_mutex_lock(&best->mutex);
--best->liveJobs;
liveJobs = best->liveJobs;
/* If the new dictionary is better */
if (compressedSize < best->compressedSize) {
/* Allocate space if necessary */
if (!best->dict || best->dictSize < dictSize) {
if (best->dict) {
free(best->dict);
}
best->dict = malloc(dictSize);
if (!best->dict) {
best->compressedSize = ERROR(GENERIC);
best->dictSize = 0;
return;
}
}
/* Save the dictionary, parameters, and size */
memcpy(best->dict, dict, dictSize);
best->dictSize = dictSize;
best->parameters = parameters;
best->compressedSize = compressedSize;
}
pthread_mutex_unlock(&best->mutex);
if (liveJobs == 0) {
pthread_cond_broadcast(&best->cond);
}
}
}
/**
* Parameters for COVER_tryParameters().
*/
typedef struct COVER_tryParameters_data_s {
const COVER_ctx_t *ctx;
COVER_best_t *best;
size_t dictBufferCapacity;
COVER_params_t parameters;
} COVER_tryParameters_data_t;
/**
* Tries a set of parameters and upates the COVER_best_t with the results.
* This function is thread safe if zstd is compiled with multithreaded support.
* It takes its parameters as an *OWNING* opaque pointer to support threading.
*/
static void COVER_tryParameters(void *opaque) {
/* Save parameters as local variables */
COVER_tryParameters_data_t *const data = (COVER_tryParameters_data_t *)opaque;
const COVER_ctx_t *const ctx = data->ctx;
const COVER_params_t parameters = data->parameters;
size_t dictBufferCapacity = data->dictBufferCapacity;
size_t totalCompressedSize = ERROR(GENERIC);
/* Allocate space for hash table, dict, and freqs */
COVER_map_t activeDmers;
BYTE *const dict = (BYTE * const)malloc(dictBufferCapacity);
U32 *freqs = (U32 *)malloc(ctx->suffixSize * sizeof(U32));
if (!COVER_map_init(&activeDmers, parameters.k - parameters.d + 1)) {
DISPLAYLEVEL(1, "Failed to allocate dmer map: out of memory\n");
goto _cleanup;
}
if (!dict || !freqs) {
DISPLAYLEVEL(1, "Failed to allocate buffers: out of memory\n");
goto _cleanup;
}
/* Copy the frequencies because we need to modify them */
memcpy(freqs, ctx->freqs, ctx->suffixSize * sizeof(U32));
/* Build the dictionary */
{
const size_t tail = COVER_buildDictionary(ctx, freqs, &activeDmers, dict,
dictBufferCapacity, parameters);
const ZDICT_params_t zdictParams = COVER_translateParams(parameters);
dictBufferCapacity = ZDICT_finalizeDictionary(
dict, dictBufferCapacity, dict + tail, dictBufferCapacity - tail,
ctx->samples, ctx->samplesSizes, (unsigned)ctx->nbSamples, zdictParams);
if (ZDICT_isError(dictBufferCapacity)) {
DISPLAYLEVEL(1, "Failed to finalize dictionary\n");
goto _cleanup;
}
}
/* Check total compressed size */
{
/* Pointers */
ZSTD_CCtx *cctx;
ZSTD_CDict *cdict;
void *dst;
/* Local variables */
size_t dstCapacity;
size_t i;
/* Allocate dst with enough space to compress the maximum sized sample */
{
size_t maxSampleSize = 0;
for (i = 0; i < ctx->nbSamples; ++i) {
maxSampleSize = MAX(ctx->samplesSizes[i], maxSampleSize);
}
dstCapacity = ZSTD_compressBound(maxSampleSize);
dst = malloc(dstCapacity);
}
/* Create the cctx and cdict */
cctx = ZSTD_createCCtx();
cdict =
ZSTD_createCDict(dict, dictBufferCapacity, parameters.compressionLevel);
if (!dst || !cctx || !cdict) {
goto _compressCleanup;
}
/* Compress each sample and sum their sizes (or error) */
totalCompressedSize = 0;
for (i = 0; i < ctx->nbSamples; ++i) {
const size_t size = ZSTD_compress_usingCDict(
cctx, dst, dstCapacity, ctx->samples + ctx->offsets[i],
ctx->samplesSizes[i], cdict);
if (ZSTD_isError(size)) {
totalCompressedSize = ERROR(GENERIC);
goto _compressCleanup;
}
totalCompressedSize += size;
}
_compressCleanup:
ZSTD_freeCCtx(cctx);
ZSTD_freeCDict(cdict);
if (dst) {
free(dst);
}
}
_cleanup:
COVER_best_finish(data->best, totalCompressedSize, parameters, dict,
dictBufferCapacity);
free(data);
COVER_map_destroy(&activeDmers);
if (dict) {
free(dict);
}
if (freqs) {
free(freqs);
}
}
ZDICTLIB_API size_t COVER_optimizeTrainFromBuffer(void *dictBuffer,
size_t dictBufferCapacity,
const void *samplesBuffer,
const size_t *samplesSizes,
unsigned nbSamples,
COVER_params_t *parameters) {
/* constants */
const unsigned nbThreads = parameters->nbThreads;
const unsigned kMinD = parameters->d == 0 ? 6 : parameters->d;
const unsigned kMaxD = parameters->d == 0 ? 16 : parameters->d;
const unsigned kMinK = parameters->k == 0 ? kMaxD : parameters->k;
const unsigned kMaxK = parameters->k == 0 ? 2048 : parameters->k;
const unsigned kSteps = parameters->steps == 0 ? 32 : parameters->steps;
const unsigned kStepSize = MAX((kMaxK - kMinK) / kSteps, 1);
const unsigned kIterations =
(1 + (kMaxD - kMinD) / 2) * (1 + (kMaxK - kMinK) / kStepSize);
/* Local variables */
const int displayLevel = parameters->notificationLevel;
unsigned iteration = 1;
unsigned d;
unsigned k;
COVER_best_t best;
POOL_ctx *pool = NULL;
/* Checks */
if (kMinK < kMaxD || kMaxK < kMinK) {
LOCALDISPLAYLEVEL(displayLevel, 1, "Incorrect parameters\n");
return ERROR(GENERIC);
}
if (nbSamples == 0) {
DISPLAYLEVEL(1, "Cover must have at least one input file\n");
return ERROR(GENERIC);
}
if (dictBufferCapacity < ZDICT_DICTSIZE_MIN) {
DISPLAYLEVEL(1, "dictBufferCapacity must be at least %u\n",
ZDICT_DICTSIZE_MIN);
return ERROR(dstSize_tooSmall);
}
if (nbThreads > 1) {
pool = POOL_create(nbThreads, 1);
if (!pool) {
return ERROR(memory_allocation);
}
}
/* Initialization */
COVER_best_init(&best);
/* Turn down global display level to clean up display at level 2 and below */
g_displayLevel = parameters->notificationLevel - 1;
/* Loop through d first because each new value needs a new context */
LOCALDISPLAYLEVEL(displayLevel, 2, "Trying %u different sets of parameters\n",
kIterations);
for (d = kMinD; d <= kMaxD; d += 2) {
/* Initialize the context for this value of d */
COVER_ctx_t ctx;
LOCALDISPLAYLEVEL(displayLevel, 3, "d=%u\n", d);
if (!COVER_ctx_init(&ctx, samplesBuffer, samplesSizes, nbSamples, d)) {
LOCALDISPLAYLEVEL(displayLevel, 1, "Failed to initialize context\n");
COVER_best_destroy(&best);
return ERROR(GENERIC);
}
/* Loop through k reusing the same context */
for (k = kMinK; k <= kMaxK; k += kStepSize) {
/* Prepare the arguments */
COVER_tryParameters_data_t *data = (COVER_tryParameters_data_t *)malloc(
sizeof(COVER_tryParameters_data_t));
LOCALDISPLAYLEVEL(displayLevel, 3, "k=%u\n", k);
if (!data) {
LOCALDISPLAYLEVEL(displayLevel, 1, "Failed to allocate parameters\n");
COVER_best_destroy(&best);
COVER_ctx_destroy(&ctx);
return ERROR(GENERIC);
}
data->ctx = &ctx;
data->best = &best;
data->dictBufferCapacity = dictBufferCapacity;
data->parameters = *parameters;
data->parameters.k = k;
data->parameters.d = d;
data->parameters.steps = kSteps;
/* Check the parameters */
if (!COVER_checkParameters(data->parameters)) {
DISPLAYLEVEL(1, "Cover parameters incorrect\n");
continue;
}
/* Call the function and pass ownership of data to it */
COVER_best_start(&best);
if (pool) {
POOL_add(pool, &COVER_tryParameters, data);
} else {
COVER_tryParameters(data);
}
/* Print status */
LOCALDISPLAYUPDATE(displayLevel, 2, "\r%u%% ",
(U32)((iteration * 100) / kIterations));
++iteration;
}
COVER_best_wait(&best);
COVER_ctx_destroy(&ctx);
}
LOCALDISPLAYLEVEL(displayLevel, 2, "\r%79s\r", "");
/* Fill the output buffer and parameters with output of the best parameters */
{
const size_t dictSize = best.dictSize;
if (ZSTD_isError(best.compressedSize)) {
COVER_best_destroy(&best);
return best.compressedSize;
}
*parameters = best.parameters;
memcpy(dictBuffer, best.dict, dictSize);
COVER_best_destroy(&best);
POOL_free(pool);
return dictSize;
}
}
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