changelog

This library is a C port of the implementation of Limited-memory Broyden-Fletcher-Goldfarb-Shanno (L

2009-02-28  Naoaki Okazaki  <okazaki at chokkan org>

	* libLBFGS 1.7:
	- Improved OWL-QN routines for stability.
	- Removed the support of OWL-QN method in MoreThuente algorithm
	  because it accidentally fails in early stages of iterations for some
	  objectives. Because of this change, the OW-LQN method must be used
	  with the backtracking algorithm (LBFGS_LINESEARCH_BACKTRACKING), or
	  the library returns LBFGSERR_INVALID_LINESEARCH.
	- Renamed line search algorithms as follows:
	    - LBFGS_LINESEARCH_BACKTRACKING: regular Wolfe condition.
	    - LBFGS_LINESEARCH_BACKTRACKING_LOOSE: regular Wolfe condition.
	    - LBFGS_LINESEARCH_BACKTRACKING_STRONG: strong Wolfe condition.
	- Source code clean-up.


2008-11-02  Naoaki Okazaki  <okazaki at chokkan org>

	* libLBFGS 1.6:
	- Improved line-search algorithm with strong Wolfe condition, which
	  was contributed by Takashi Imamichi. This routine is now default for
	  LBFGS_LINESEARCH_BACKTRACKING. The previous line search algorithm
	  with regular Wolfe condition is still available as
	  LBFGS_LINESEARCH_BACKTRACKING_LOOSE.
	- Configurable stop index for L1-norm computation. A member variable
	  lbfgs_parameter_t::orthantwise_end was added to specify the index
	  number at which the library stops computing the L1 norm of the
	  variables. This is useful to prevent some variables from being
	  regularized by the OW-LQN method.
	- A sample program written in C++ (sample/sample.cpp).


2008-07-10  Naoaki Okazaki  <okazaki at chokkan org>

	* libLBFGS 1.5:
	- Configurable starting index for L1-norm computation. A member
	  variable lbfgs_parameter_t::orthantwise_start was added to specify
	  the index number from which the library computes the L1 norm of the
	  variables.
	- Fixed a zero-division error when the initial variables have already
	  been a minimizer (reported by Takashi Imamichi). In this case, the
	  library returns LBFGS_ALREADY_MINIMIZED status code.
	- Defined LBFGS_SUCCESS status code as zero; removed unused constants,
	  LBFGSFALSE and LBFGSTRUE.
	- Fixed a compile error in an implicit down-cast.


2008-04-25  Naoaki Okazaki  <okazaki at chokkan org>

	* libLBFGS 1.4:
	- Configurable line search algorithms. A member variable
	  lbfgs_parameter_t::linesearch was added to choose either MoreThuente
	  method (LBFGS_LINESEARCH_MORETHUENTE) or backtracking algorithm
	  (LBFGS_LINESEARCH_BACKTRACKING).
	- Fixed a bug: the previous version did not compute psuedo-gradients
	  properly in the line search routines for OW-LQN. This bug might quit
	  an iteration process too early when the OW-LQN routine was activated
	  (0 < lbfgs_parameter_t::orthantwise_c).
	- Configure script for POSIX environments.
	- SSE/SSE2 optimizations with GCC.
	- New functions lbfgs_malloc and lbfgs_free to use SSE/SSE2 routines
	  transparently. It is uncessary to use these functions for libLBFGS
	  built without SSE/SSE2 routines; you can still use any memory
	  allocators if SSE/SSE2 routines are disabled in libLBFGS.


2007-12-16  Naoaki Okazaki  <okazaki at chokkan org>

	* libLBFGS 1.3:
	- An API change. An argument was added to lbfgs() function to receive
	  the final value of the objective function. This argument can be set
	  to NULL if the final value is unnecessary.
	- Fixed a null-pointer bug in the sample code (reported by Takashi
	  Imamichi).
	- Added build scripts for Microsoft Visual Studio 2005 and GCC.
	- Added README file.
	

2007-12-13  Naoaki Okazaki  <okazaki at chokkan org>

	* libLBFGS 1.2:
	- Fixed a serious bug in orthant-wise L-BFGS. An important variable
	  was used without initialization.
	- Configurable L-BFGS parameters (number of limited memories, epsilon).
	
	
2007-12-01  Naoaki Okazaki  <okazaki at chokkan org>

	* libLBFGS 1.1:
	- Implemented orthant-wise L-BFGS.
	- Implemented lbfgs_parameter_init() function.
	- Fixed several bugs.
	- API documentation.
	
	
2007-09-20  Naoaki Okazaki  <okazaki at chokkan org>

	* libLBFGS 1.0
	- Initial release.