view release on metacpan or  search on metacpan

ext/zstd/programs/zstd.1.md  view on Meta::CPAN

    The minimum _ovlog_ is 0, and the maximum is 9.
    1 means "no overlap", hence completely independent jobs.
    9 means "full overlap", meaning up to `windowSize` is reloaded from previous job.
    Reducing _ovlog_ by 1 reduces the reloaded amount by a factor 2.
    For example, 8 means "windowSize/2", and 6 means "windowSize/8".
    Value 0 is special and means "default" : _ovlog_ is automatically determined by `zstd`.
    In which case, _ovlog_ will range from 6 to 9, depending on selected _strat_.

- `ldmHashLog`=_lhlog_, `lhlog`=_lhlog_:
    Specify the maximum size for a hash table used for long distance matching.

    This option is ignored unless long distance matching is enabled.

    Bigger hash tables usually improve compression ratio at the expense of more
    memory during compression and a decrease in compression speed.

    The minimum _lhlog_ is 6 and the maximum is 26 (default: 20).

- `ldmMinMatch`=_lmml_, `lmml`=_lmml_:
    Specify the minimum searched length of a match for long distance matching.

    This option is ignored unless long distance matching is enabled.

    Larger/very small values usually decrease compression ratio.

    The minimum _lmml_ is 4 and the maximum is 4096 (default: 64).

- `ldmBucketSizeLog`=_lblog_, `lblog`=_lblog_:
    Specify the size of each bucket for the hash table used for long distance
    matching.

    This option is ignored unless long distance matching is enabled.

    Larger bucket sizes improve collision resolution but decrease compression
    speed.

    The minimum _lblog_ is 0 and the maximum is 8 (default: 3).

- `ldmHashRateLog`=_lhrlog_, `lhrlog`=_lhrlog_:
    Specify the frequency of inserting entries into the long distance matching
    hash table.

    This option is ignored unless long distance matching is enabled.

    Larger values will improve compression speed. Deviating far from the
    default value will likely result in a decrease in compression ratio.

    The default value is `wlog - lhlog`.

### Example
The following parameters sets advanced compression options to something
similar to predefined level 19 for files bigger than 256 KB:

`--zstd`=wlog=23,clog=23,hlog=22,slog=6,mml=3,tlen=48,strat=6

### -B#:
Select the size of each compression job.
This parameter is available only when multi-threading is enabled.
Default value is `4 * windowSize`, which means it varies depending on compression level.
`-B#` makes it possible to select a custom value.
Note that job size must respect a minimum value which is enforced transparently.
This minimum is either 1 MB, or `overlapSize`, whichever is largest.

BUGS
----
Report bugs at: https://github.com/facebook/zstd/issues

AUTHOR
------
Yann Collet