Yann Collet [Thu, 7 Jun 2018 22:12:13 +0000 (15:12 -0700)]
fuzzer: make negative compression level fail
result of ZSTD_compress_advanced()
is different from ZSTD_compress_generic()
when using negative compression levels
because the disabling of huffman compression is not passed in parameters.
Yann Collet [Thu, 7 Jun 2018 20:53:30 +0000 (13:53 -0700)]
clean ZSTD_compress() initialization
The (pretty old) code inside ZSTD_compress()
was making some pretty bold assumptions
on what's inside a CCtx and how to init it.
This is pretty fragile by design.
CCtx content evolve.
Knowledge of how to handle that should be concentrate in one place.
A side effect of this strategy
is that ZSTD_compress() wouldn't check for BMI2 capability,
and is therefore missing out some potential speed opportunity.
This patch makes ZSTD_compress() use
the same initialization and release functions
as the normal creator / destructor ones.
Measured on my laptop, with a custom version of bench
manually modified to use ZSTD_compress() (instead of the advanced API) :
This patch :
1#silesia.tar : 211984896 -> 73651053 (2.878), 312.2 MB/s , 723.8 MB/s
2#silesia.tar : 211984896 -> 70163650 (3.021), 226.2 MB/s , 649.8 MB/s
3#silesia.tar : 211984896 -> 66996749 (3.164), 169.4 MB/s , 636.7 MB/s
4#silesia.tar : 211984896 -> 65998319 (3.212), 136.7 MB/s , 619.2 MB/s
dev branch :
1#silesia.tar : 211984896 -> 73651053 (2.878), 291.7 MB/s , 727.5 MB/s
2#silesia.tar : 211984896 -> 70163650 (3.021), 216.2 MB/s , 655.7 MB/s
3#silesia.tar : 211984896 -> 66996749 (3.164), 162.2 MB/s , 633.1 MB/s
4#silesia.tar : 211984896 -> 65998319 (3.212), 130.6 MB/s , 618.6 MB/s
Yann Collet [Thu, 7 Jun 2018 19:18:47 +0000 (12:18 -0700)]
disable aarch64 test on travis CI
there's a bug on travis' ld
> collect2: error: ld terminated with signal 11 [Segmentation fault], core dumped
I cannot reproduce it.
Note that travis' ld version is 2.24
while the one in my Linux VM is 2.26.1.
ld is part of binutils, so it's pretty hard to change.
I would expect the bug to no longer be triggered after some random code change.
To be re-enabled later.
Yann Collet [Wed, 6 Jun 2018 22:04:12 +0000 (15:04 -0700)]
context can be sized down even with constant parameters
when parameters are "equivalent",
the context is re-used in continue mode,
hence needed workspace size is not recalculated.
This incidentally also evades the size-down check and action.
This patch intercepts the "continue mode"
so that the size-down check and action is actually triggered.
Yann Collet [Fri, 1 Jun 2018 22:18:32 +0000 (15:18 -0700)]
Fixed a nasty corruption bug
recently introduce into the new dictionary mode.
The bug could be reproduced with this command :
./zstreamtest -v --opaqueapi --no-big-tests -s4092 -t639
error was in function ZSTD_count_2segments() :
the beginning of the 2nd segment corresponds to prefixStart
and not the beginning of the current block (istart == src).
This would result in comparing the wrong byte.
Yann Collet [Sat, 26 May 2018 00:41:16 +0000 (17:41 -0700)]
changed dynamic fse threshold for offset
recent experienced showed that
default distribution table for offset
can get it wrong pretty quickly with the nb of symbols,
while it remains a reasonable choice much longer for lengths symbols.
Changed the formula,
so that dynamic threshold is now 32 symbols for offsets.
It remains at 64 symbols for lengths.
Yann Collet [Fri, 25 May 2018 22:19:52 +0000 (15:19 -0700)]
btultra accepts blocks with poorer compression ratio
zstd rejects blocks which do not compress by at least a certain amount.
In which case, such block is simply emitted uncompressed (even if a little bit of compression could be achieved).
This is better for decompression speed, hence for energy.
The logic is controlled by ZSTD_minGain().
The rule is applied uniformly, at all compression levels.
This change makes btultra accepts blocks with poor compression ratios.
We presume that users of btultra mode prefers compression ratio over some decompress speed gains.
The threshold for minimum gain is lowered for btultra
from s>>6 (~1.5% minimum gain)
to s>>7 (~0.8% minimum gain).
This is a prudent change.
Not sure if it's large enough.