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* `--train-fastcover[=k#,d=#,f=#,steps=#,split=#,accel=#]`:
    Same as cover but with extra parameters _f_ and _accel_ and different default value of split
    If _split_ is not specified, then it tries _split_ = 75.
    If _f_ is not specified, then it tries _f_ = 20.
    Requires that 0 < _f_ < 32.
    If _accel_ is not specified, then it tries _accel_ = 1.
    Requires that 0 < _accel_ <= 10.
    Requires that _d_ = 6 or _d_ = 8.

    _f_ is log of size of array that keeps track of frequency of subsegments of size _d_.
    The subsegment is hashed to an index in the range [0,2^_f_ - 1].
    It is possible that 2 different subsegments are hashed to the same index, and they are considered as the same subsegment when computing frequency.
    Using a higher _f_ reduces collision but takes longer.

    Examples:

    `zstd --train-fastcover FILEs`

    `zstd --train-fastcover=d=8,f=15,accel=2 FILEs`

* `--train-legacy[=selectivity=#]`:
    Use legacy dictionary builder algorithm with the given dictionary
    _selectivity_ (default: 9).
    The smaller the _selectivity_ value, the denser the dictionary,
    improving its efficiency but reducing its achievable maximum size.
    `--train-legacy=s=#` is also accepted.

    Examples:

    `zstd --train-legacy FILEs`

    `zstd --train-legacy=selectivity=8 FILEs`


BENCHMARK
---------

* `-b#`:
    benchmark file(s) using compression level #
* `-e#`:
    benchmark file(s) using multiple compression levels, from `-b#` to `-e#` (inclusive)
* `-i#`:
    minimum evaluation time, in seconds (default: 3s), benchmark mode only
* `-B#`, `--block-size=#`:
    cut file(s) into independent chunks of size # (default: no chunking)
* `--priority=rt`:
    set process priority to real-time

**Output Format:** CompressionLevel#Filename: InputSize -> OutputSize (CompressionRatio), CompressionSpeed, DecompressionSpeed

**Methodology:** For both compression and decompression speed, the entire input is compressed/decompressed in-memory to measure speed. A run lasts at least 1 sec, so when files are small, they are compressed/decompressed several times per run, in ord...

ADVANCED COMPRESSION OPTIONS
----------------------------
### -B#:
Specify the size of each compression job.
This parameter is only available when multi-threading is enabled.
Each compression job is run in parallel, so this value indirectly impacts the nb of active threads.
Default job size varies depending on compression level (generally  `4 * windowSize`).
`-B#` makes it possible to manually select a custom size.
Note that job size must respect a minimum value which is enforced transparently.
This minimum is either 512 KB, or `overlapSize`, whichever is largest.
Different job sizes will lead to non-identical compressed frames.

### --zstd[=options]:
`zstd` provides 22 predefined regular compression levels plus the fast levels.
This compression level is translated internally into a number of specific parameters that actually control the behavior of the compressor.
(You can see the result of this translation with `--show-default-cparams`.)
These specific parameters can be overridden with advanced compression options.
The _options_ are provided as a comma-separated list.
You may specify only the options you want to change and the rest will be
taken from the selected or default compression level.
The list of available _options_:

- `strategy`=_strat_, `strat`=_strat_:
    Specify a strategy used by a match finder.

    There are 9 strategies numbered from 1 to 9, from fastest to strongest:
    1=`ZSTD_fast`, 2=`ZSTD_dfast`, 3=`ZSTD_greedy`,
    4=`ZSTD_lazy`, 5=`ZSTD_lazy2`, 6=`ZSTD_btlazy2`,
    7=`ZSTD_btopt`, 8=`ZSTD_btultra`, 9=`ZSTD_btultra2`.

- `windowLog`=_wlog_, `wlog`=_wlog_:
    Specify the maximum number of bits for a match distance.

    The higher number of increases the chance to find a match which usually
    improves compression ratio.
    It also increases memory requirements for the compressor and decompressor.
    The minimum _wlog_ is 10 (1 KiB) and the maximum is 30 (1 GiB) on 32-bit
    platforms and 31 (2 GiB) on 64-bit platforms.

    Note: If `windowLog` is set to larger than 27, `--long=windowLog` or
    `--memory=windowSize` needs to be passed to the decompressor.

- `hashLog`=_hlog_, `hlog`=_hlog_:
    Specify the maximum number of bits for a hash table.

    Bigger hash tables cause fewer collisions which usually makes compression
    faster, but requires more memory during compression.

    The minimum _hlog_ is 6 (64 entries / 256 B) and the maximum is 30 (1B entries / 4 GiB).

- `chainLog`=_clog_, `clog`=_clog_:
    Specify the maximum number of bits for the secondary search structure,
    whose form depends on the selected `strategy`.

    Higher numbers of bits increases the chance to find a match which usually
    improves compression ratio.
    It also slows down compression speed and increases memory requirements for
    compression.
    This option is ignored for the `ZSTD_fast` `strategy`, which only has the primary hash table.

    The minimum _clog_ is 6 (64 entries / 256 B) and the maximum is 29 (512M entries / 2 GiB) on 32-bit platforms
    and 30 (1B entries / 4 GiB) on 64-bit platforms.

- `searchLog`=_slog_, `slog`=_slog_:
    Specify the maximum number of searches in a hash chain or a binary tree
    using logarithmic scale.

    More searches increases the chance to find a match which usually increases
    compression ratio but decreases compression speed.