Log of /trunk/misc/table/src/TFileIter.cxx
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Revision
41088 -
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Modified
Sat Oct 1 19:38:48 2011 UTC (3 years, 3 months ago) by
pcanal
File length: 21707 byte(s)
Diff to
previous 39696
In table, use TDirectory::TContext to save/restore gDirectory rather than table's own mechanism (in preparation to gFile becoming read only)
Revision
39696 -
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Modified
Mon Jun 13 21:35:34 2011 UTC (3 years, 7 months ago) by
pcanal
File length: 21848 byte(s)
Diff to
previous 35878
From David Dagenhart:
Implement an option to allow ROOT to use the LZMA compression
algorithm to compress data instead of the ZLIB compression algorithm.
LZMA compression typically results in smaller files, but takes more
CPU time to compress data. To use the new feature, the external XZ
package must be installed when ROOT is configured and built:
Download 5.0.3 from here http://tukaani.org/xz/
and make sure to configure with fPIC:
./configure CFLAGS='-fPIC'
Then the client C++ code must call routines to explicitly request LZMA
compression.
ZLIB compression is still the default.
Setting the Compression Level and Algorithm:
There are three equivalent ways to set the compression level and
algorithm. For example, to set the compression to the LZMA algorithm
and compression level 5.
1. TFile f(filename, option, title);
f.SetCompressionSettings(ROOT::CompressionSettings(ROOT::kLZMA, 5));
OR
2. TFile f(filename, option, title, ROOT::CompressionSettings(ROOT::kLZMA, 5));
OR
3. TFile f(filename, option, title);
f.SetCompressionAlgorithm(ROOT::kLZMA);
f.SetCompressionLevel(5);
These methods work for TFile, TBranch, TMessage, TSocket, and TBufferXML.
The compression algorithm and level settings only affect compression of
data after they have been set. TFile passes its settings to its branches
only at the time the branches are created. This can be overidden by
explicitly setting the level and algorithm for the branch. These classes
also have the following methods to access the algorithm and level for
compression.
Int_t GetCompressionAlgorithm() const;
Int_t GetCompressionLevel() const;
Int_t GetCompressionSettings() const;
If the compression level is set to 0, then no compression will be
done. All of the currently supported algorithms allow the level to be
set to any value from 1 to 9. The higher the level, the larger the
compression factors will be (smaller compressed data size). The
tradeoff is that for higher levels more CPU time is used for
compression and possibly more memory. The ZLIB algorithm takes less
CPU time during compression than the LZMA algorithm, but the LZMA
algorithm usually delivers higher compression factors.
The header file core/zip/inc/Compression.h declares the function
"CompressionSettings" and the enumeration for the algorithms.
Currently the following selections can be made for the algorithm:
kZLIB (1), kLZMA (2), kOldCompressionAlgo (3), and kUseGlobalSetting
(0). The last option refers to an older interface used to control the
algorithm that is maintained for backward compatibility. The following
function is defined in core/zip/inc/Bits.h and it set the global
variable.
R__SetZipMode(int algorithm)
If the algorithm is set to kUseGlobalSetting (0), the global variable
controls the algorithm for compression operations. This is the
default and the default value for the global variable is kZLIB.
Note that the LZMA algorithm will only be available if the LZMA
libraries from the XZ package were available when the ROOT executable
being used was configured and built. If you are building ROOT and want
LZMA then you must do something similar to the following if XZ is not
already installed on your system.
Download XZ version 5.0.3 from http://tukaani.org/xz/
unwind the tarball
cd xz-5.0.3
./configure CFLAGS='-fPIC'
make
ROOT was tested with version 5.0.3 of XZ. It might work with earlier
versions and will probably work with later versions of XZ.
Then either use "make install" to put the library and headers into
/usr/local/* so the scripts building ROOT can find them or use
arguments to the ROOT configure script to point to the proper
directories containing the XZ library and headers. These are the
library and the included header (lzma.h includes other headers in the
lzma subdirectory).
src/liblzma/.libs/liblzma.a
src/liblzma/api/lzma.h
WARNING: Data compressed with the LZMA algorithm cannot be read by
ROOT executables that were not built with LZMA support.
Revision
23733 -
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Modified
Wed May 7 18:59:02 2008 UTC (6 years, 8 months ago) by
brun
File length: 21278 byte(s)
Diff to
previous 23254
From valeri fine:
- Merge with STAR local version to allow iteration of the nested TDirectory (Thanks Rene Brun for the idea)
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