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  • Xu Chen Xu Chen chenxu
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  1. Jul 04, 2013
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  25. Sep 13, 2011
    • Philippe Canal's avatar
      From Chris Jones: · 7de5e0a0
      Philippe Canal authored 
      Put in place the infrastructure to optimize the I/O writes in the same way we optimized the I/O reads.

Rename TBuffer::ReadSequence to TBuffer::ApplySequence as they can be used both for reading and writing.  The 3 new signatures:

1. virtual Int_t ApplySequence(const TStreamerInfoActions::TActionSequence &sequence, void *object);      
2. virtual Int_t ApplySequenceVecPtr(const TStreamerInfoActions::TActionSequence &sequence, void *start_collection, void *end_collection);      
3. virtual Int_t ApplySequence(const TStreamerInfoActions::TActionSequence &sequence, void *start_collection, void *end_collection);

The 1st version is optimized to read a single object. The 2nd version is optimized to read the content of TClonesArrays and vectors of pointers to objects.
The 3rd version is used to streamed any collections.

In TBranchElement, introduce a set FillLeaves member functions to precalculate many of the (existing) conditional.  Introduction support for the StreamerInfo write actions and sequences.


git-svn-id: http://root.cern.ch/svn/root/trunk@40872 27541ba8-7e3a-0410-8455-c3a389f83636
      7de5e0a0
  27. Aug 23, 2011
  29. Aug 19, 2011
    • Philippe Canal's avatar
      From Bruno Lenzi: TEntryListArray · f95f142d
      Philippe Canal authored 
      TEntryListArray is an extension of TEntryList, used to hold selected entries and subentries (sublists) of a TTree. It is useful in case of a TTree with containers (vectors, arrays, ...). A typical example is the case when each entry of a TTree corresponds to physics events and each subentry (index of arrays) represents a particle.

Its main purpose is to improve the performance of a code that needs to apply complex selections (cuts) on TTree::Draw multiple times. Evaluating such cuts can be time consuming for large trees due to the need for loading the associated information (branches). This operation is done once with the use of a TEntryListArray. Subsequent calls to TTree::Draw only need to load the requested branches for histogramming, while using only the entries and subentries that satisfied the previous selection.

TTree/TSelectorDraw: use of TEntryListArray to select entries and subentries. If the option "entrylistarray" is specified, a TEntryListArray is created and filled with the entries and subentries that pass the given selection. If TTree::Draw is called after a TEntryList is set, only the selected entries and subentries are used to fill histograms or create new entrylists.


git-svn-id: http://root.cern.ch/svn/root/trunk@40643 27541ba8-7e3a-0410-8455-c3a389f83636
      f95f142d
  31. Aug 14, 2011
  33. Jun 13, 2011
    • Philippe Canal's avatar
      From David Dagenhart: · 02d8d542
      Philippe Canal authored 
      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.


git-svn-id: http://root.cern.ch/svn/root/trunk@39696 27541ba8-7e3a-0410-8455-c3a389f83636
      02d8d542
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