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[cover] Make optimization faster

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Nick Terrell
2017-05-02 11:02:48 -07:00
parent f2d9ef1dc0
commit 020b960e13
3 changed files with 8 additions and 11 deletions
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programs/zstd.1.md
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@@ -194,9 +194,9 @@ Typical gains range from 10% (at 64KB) to x5 better (at <1KB).
* `--optimize-cover[=steps=#,k=#,d=#]`:
If _steps_ is not specified, the default value of 32 is used.
If _k_ is not specified, the _k_ values in [16, 2048] are checked for each
If _k_ is not specified, the _k_ values in [48, 2048] are checked for each
value of _d_.
If _d_ is not specified, the values checked are [6, 8, ..., 16].
If _d_ is not specified, the values checked are [6, 8].
Runs the cover dictionary builder for each parameter set
and saves the optimal parameters and dictionary.
@@ -204,15 +204,12 @@ Typical gains range from 10% (at 64KB) to x5 better (at <1KB).
Supports multithreading if `zstd` is compiled with threading support.
The parameter _k_ is more sensitive than _d_, and is faster to optimize over.
Suggested use is to run with a _steps_ <= 32 with neither _k_ nor _d_ set.
Once it completes, use the value of _d_ it selects with a higher _steps_
(in the range [256, 1024]).
Examples :
`zstd --train --optimize-cover FILEs`
`zstd --train --optimize-cover=d=d,steps=512 FILEs`
`zstd --train --optimize-cover=d=8,steps=512 FILEs`
BENCHMARK