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Merge branch 'dev' into adapt

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Yann Collet
2018-09-19 12:43:42 -07:00
parent c71c4f23d7 c8ff5200f9
commit 2f78228f65
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@@ -207,9 +207,10 @@ Compression of small files similar to the sample set will be greatly improved.
(for example, 10 MB for a 100 KB dictionary).
Supports multithreading if `zstd` is compiled with threading support.
Additional parameters can be specified with `--train-cover`.
Additional parameters can be specified with `--train-fastcover`.
The legacy dictionary builder can be accessed with `--train-legacy`.
Equivalent to `--train-cover=d=8,steps=4`.
The cover dictionary builder can be accessed with `--train-cover`.
Equivalent to `--train-fastcover=d=8,steps=4`.
* `-o file`:
Dictionary saved into `file` (default name: dictionary).
* `--maxdict=#`:
@@ -261,6 +262,26 @@ Compression of small files similar to the sample set will be greatly improved.
`zstd --train-cover=k=50,split=60 FILEs`
* `--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).