annotate contrib/python-zstandard/zstd/dictBuilder/cover.h @ 44413:4cabeea6d214

hgext: start building a library for simple hooks

Many workflows depend on hooks to enforce certain policies, e.g. to
prevent forced pushes. The Mercurial Guide includes some cases and
Google can help finding others, but it can save users a lot of time
if hg itself has a couple of examples for further customization.

Differential Revision: https://phab.mercurial-scm.org/D6825

#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"

/**
 * 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 {
  ZSTD_pthread_mutex_t mutex;
  ZSTD_pthread_cond_t cond;
  size_t liveJobs;
  void *dict;
  size_t dictSize;
  ZDICT_cover_params_t parameters;
  size_t compressedSize;
} COVER_best_t;

/**
 * A segment is a range in the source as well as the score of the segment.
 */
typedef struct {
  U32 begin;
  U32 end;
  U32 score;
} COVER_segment_t;

/**
 *Number of epochs and size of each epoch.
 */
typedef struct {
  U32 num;
  U32 size;
} COVER_epoch_info_t;

/**
 * Struct used for the dictionary selection function.
 */
typedef struct COVER_dictSelection {
  BYTE* dictContent;
  size_t dictSize;
  size_t totalCompressedSize;
} COVER_dictSelection_t;

/**
 * Computes the number of epochs and the size of each epoch.
 * We will make sure that each epoch gets at least 10 * k bytes.
 *
 * The COVER algorithms divide the data up into epochs of equal size and
 * select one segment from each epoch.
 *
 * @param maxDictSize The maximum allowed dictionary size.
 * @param nbDmers     The number of dmers we are training on.
 * @param k           The parameter k (segment size).
 * @param passes      The target number of passes over the dmer corpus.
 *                    More passes means a better dictionary.
 */
COVER_epoch_info_t COVER_computeEpochs(U32 maxDictSize, U32 nbDmers,
                                       U32 k, U32 passes);

/**
 * Warns the user when their corpus is too small.
 */
void COVER_warnOnSmallCorpus(size_t maxDictSize, size_t nbDmers, int displayLevel);

/**
 *  Checks total compressed size of a dictionary
 */
size_t COVER_checkTotalCompressedSize(const ZDICT_cover_params_t parameters,
                                      const size_t *samplesSizes, const BYTE *samples,
                                      size_t *offsets,
                                      size_t nbTrainSamples, size_t nbSamples,
                                      BYTE *const dict, size_t dictBufferCapacity);

/**
 * Returns the sum of the sample sizes.
 */
size_t COVER_sum(const size_t *samplesSizes, unsigned nbSamples) ;

/**
 * Initialize the `COVER_best_t`.
 */
void COVER_best_init(COVER_best_t *best);

/**
 * Wait until liveJobs == 0.
 */
void COVER_best_wait(COVER_best_t *best);

/**
 * Call COVER_best_wait() and then destroy the COVER_best_t.
 */
void COVER_best_destroy(COVER_best_t *best);

/**
 * Called when a thread is about to be launched.
 * Increments liveJobs.
 */
void COVER_best_start(COVER_best_t *best);

/**
 * 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.
 */
void COVER_best_finish(COVER_best_t *best, ZDICT_cover_params_t parameters,
                       COVER_dictSelection_t selection);
/**
 * Error function for COVER_selectDict function. Checks if the return
 * value is an error.
 */
unsigned COVER_dictSelectionIsError(COVER_dictSelection_t selection);

 /**
  * Error function for COVER_selectDict function. Returns a struct where
  * return.totalCompressedSize is a ZSTD error.
  */
COVER_dictSelection_t COVER_dictSelectionError(size_t error);

/**
 * Always call after selectDict is called to free up used memory from
 * newly created dictionary.
 */
void COVER_dictSelectionFree(COVER_dictSelection_t selection);

/**
 * Called to finalize the dictionary and select one based on whether or not
 * the shrink-dict flag was enabled. If enabled the dictionary used is the
 * smallest dictionary within a specified regression of the compressed size
 * from the largest dictionary.
 */
 COVER_dictSelection_t COVER_selectDict(BYTE* customDictContent,
                       size_t dictContentSize, const BYTE* samplesBuffer, const size_t* samplesSizes, unsigned nbFinalizeSamples,
                       size_t nbCheckSamples, size_t nbSamples, ZDICT_cover_params_t params, size_t* offsets, size_t totalCompressedSize);