Stan Math Library Release Notes
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v.2.18.0 (05 September 2017)
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This is our first release with parallelism (through C++11 threads or MPI)!

New Features
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* Support for MPI parallelization with map_rect
* Support for threaded AD and a threaded map_rect implementation (#809)
* New periodic covariance function (#921)
* Integrated Boost's 1 dimensional integrator (#913)
* Added thin QR decomposition (#900)
* New `add_diag` function for adding a real or vector to the diagonal of a matrix (#871)
* New `log_inv_logit_diff` function for the log of the difference of two inverse logits (#856)
* New dot product kernel for GPs (#834)
* Vectorized many more RNGs (#833, #722, #622)
* Add `matrix_exp_action` to calculate `exp(At)*B` (#830)
* `log_mix` vectorized (#751, #664)
* New integrators from CVODES (`integrate_ode_adams`, `_bdf`) (#735)
* New `std_normal` (#609)
* New `std_normal_log` (#728)
* New GLM primitive `normal_id_glm` (#665)
* New `chol2inv` that computes a matrix's inverse from its Cholesky factor (#649)
* New `poisson_log_glm` poisson regression with log link (#647)
* New vectorized `ordered_probit` (#645)
* New `log_modified_bessel_first_kind` that expands where Bessel 1 function can be used (#640)
* New bernoulli logit GLM (#608)

Bug Fixes
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* Rising and falling factorial were not accepting negative arguments (#636)
* Fix normalizing constant for LKJ distribution (#628)

Other
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* Tweaks to `effective_sample_size` for performance and upstream compatibility (#865)
* Switch to sundials package combining CVODES and IDAS, updating versions (#779, #744)
* Now publishing the Math doxygen (http://mc-stan.org/math/)
* Faster `dirichlet_lpdf` accepting more vector types (#788)
* Upgrade to Boost 1.66 (#766)
* Improved derivatives for Gamma CDF (#780)
* Sped up `multi_normal_cholesky` (#753)
* More efficient `mdivide_right_tri` (#715)
* More efficient `integrate_ode_rk45_grad_test` (#714)
* Make algebraic solver easier to use (#703, #697)
* Begin thinking about internal compatibility for complex numbers (#643)
* Faster `pow` (#642)


v.2.17.0 (05 September 2017)
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New Features
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* New algebraic solver! (stan-dev/stan#2023, #516)
* append_array now supports vectors of vectors

Other
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* C++11 (and some of 14) now supported; see https://github.com/stan-dev/stan/wiki/Supported-C---Compilers-and-Language-Features
* Updated to Boost 1.64.0 (#599)
* Makefile refactoring (#602, others)
* New forward-mode test kit (#0557, #0568)
* replace copy args with refs (#346)

v.2.16.0 (15 June 2017)
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New Features
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* New append_array function
* Add categorical_logit_rng function

Bug Fixes
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* Align gamma_* function parameter names with documentation

Other
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* Update to Eigen 3.3.3
* Support g++ 4.9
* Fix overload logic in mdivide_left_tri_low so that it calls the var version of mdivide_left_tri where appropriate.
* Check consistent size of state and dy_dt in ode_system
* OperandsAndPartials refactor with new multivariate / nested container support
* Update LLT to inplace decomposition per eigen 3.3 doc
* Disable printf functions from CVODES


v.2.15.0 (13 April 2017)
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New Features
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* Efficient blocking algorithm for gradient of the Cholesky(#384)
* New distribution functions _lpdf / _lpmf / _lcdf / _lccdf to replace _log function (#320)
* Univariate normal distribution on sufficient statistics(#38)
* New to_matrix function for real arrays(real[]) (#467)
* New specialization of stan::math::array_builder for matrix types(#496)

Bug Fixes
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* Fixes to hypergeometric functions(#487)

Other
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* Speedup for categorical_rng(#503)
* Speedup for non-stiff ODE integration(#512)
* Refactor VectorView into scalar_seq_view(#464)


v.2.14.0 (26 December 2016)
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Bug Fixes
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* neg_binomial_2_log problem with large values of phi (#463)

Other
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* Remove check_equal() function (#398)

v2.13.0 (25 November 2016)
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New Features
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* vectorization of unary functions (#347)
* specialized gradients for cove_exp_quad for amplitude and/or length-scale
  parameters and input data (#353)
* math library is consistent with Eigen 3.2.9 and 3.3.0 (#432, #429)
* added choose(n, k) function (#400)
* added bernoulli_logit_rng function (#258)

Bug Fixes
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* beta_rng no longer returns NaN
* fixed memory issue with cholesky_decompose in reverse-mode (#415)
* no more mulitple definitions when including Stan headers in
  multiple source files (#394)
* fixed broken _MSC_VER conditionals and remove math.h includes (#370)

Other
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* chi-square test in RNG testing pulled into utility function (#412)
* error check functions are now all void functions (#382)
* remove math.h includes (#277)
* update to Boost 1.62.0 (#435)



v2.12.0 (6 September 2016)
======================================================================

New Features
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* update to Eigen 3.2.9 (#362)
* lots of unary functions vectorized (#202)
* reverse-mode gradients for matrix/matrix multiply,
  matrix/vector multiply, and vector/vector multiply
  received rewrites and significant speed ups for
  large matrices/vectors (#323)

Bug Fixes
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* fixed exception handling with CVODES for g++6 (#348)
* squashed warnings with g++6 (#345)
* enforce symmetry on cov_matrix parameter inverse transform (#342)
* added int overload for log(), exp(), log2(), and log1p() to resolve
  ambiguity with g++6 (#327)
* sort_asc and sort_desc check for NaN (#253)
* wiener_log: raise exception for tau >= y (#150)
* stopped printing matrices in check functions (#146)
* added check for positive definiteness in multi_normal_rng (#44)


Other
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* added multi-core to travis builds (#373)
* fixed makefile to recognize N_TESTS (#367)
* updated error message for check_bounded() (#332)
* made the use of stan::math namespace within the math library
  more consistent (#331)
* reimplemented integer division (#329)
* added test for multiple translation units (#328)
* updated costs for Eigen::NumTraits (#233)
* worked on getting the Math library working with Eigen 3.3-beta (#187)




v2.11.0 (27 July 2016)
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New Features
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* vectorization of a many unary math functions (#202)

Bug Fixes
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* throw exception on integer divide by 0 (#321)
* allow inclusing of Stan headers in multiple translation units (#311)





v2.10.0 (15 June 2016)
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New Features
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* append_row and append_col for scalars (stan-dev/stan #1347)
* PYTHON2 property in makefile for 2.x requirement for
  cpplint (#300)
* refactored general ODE interface and add CVODES bdf
  integrator (#262, #293, #281, #284, #288)
* rename integrate_ode to integrate_ode_rk45 (#292)
* update to Eigen 3.2.8 (#256)
* efficiency improvement in value_of and value_of_rec (#249)
* generalize dependencies in runTests.py (#247)
* untangle include dependencies, add finer headers (#246)
* std::vector version of value_of and value_of_rec (#243)
* doc for is_vector_like and more tests (#241)
* issue and pull-request templates on GitHub (#237)
* top-level includes by shape and autodiff type (#236)
* upgrade to Boost 1.60 (#221)
* unary vectorization infrastructure (#202)
* ODE integrator fails if precision not reachable (#179)

Bug Fixes
--------------------------------------------------
* fix elementwise division argument cast problem with
  operator/(matrix, var) not compiling (#290)
* fix QR decomposition segfault for no-square matrices (#286)
* fix off-by-one bug in nested Jacobian autodiff in degenerate
  set_zero_all_adjoints_nested() call (#278)
* squash compiler warnings in OperandsAndPartials (#274)
* ifdef out residual Sundials (CVODES) print statements (#257)
* fix binomial coefficient branch to remove integer division and
  rounding (#239)
* refine clean-all make target to remove .d files (#234)
* fix Jacobian bug returning transposed result (#230)
* include stdexcept so container_view header compiles (#223)






v2.9.0 (3 December 2015)
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New Features
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* Added container_view (#103)
* Improved derivative calculation for beta_cdf (#124)
* Gradients computed for cholesky_decompose (#125)
* Added functions for sparse matrix multiplication (#159)
* Changed the unit_vector transformation (#204)

Bug Fixes
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* Check inputs for cholesky_decompose (#48)
* Fixed documentation for wiener.hpp (#140)

Other
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* Cleaned up couple_ode_system for clarity (#180)
* Additional forward mode specializations (#16, #17)
* Removed unused chaintable base class (#183)
* Updated clang++ compiler options to supress warnings (#197)
* Fixed some unit tests (#199)
* Replaced top-level using statements (#207)


v2.8.0 (8 September 2015)
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New Features
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* Added standard normal quantile function (#148)
* Add sparse matrix (csr format) by dense vector multiplication (#127)
* Faster derivative calculation for cholesky (#125)
* Fixes for MSVC 2008 and 2010 (#134)

Bug Fixes
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* Fixed unit test for `mdivide_right_spd` (#153)
* Reduced compiler warnings for sing comparisons for sign functions (#151)
* Fixed gitignore for test directory (#149)
* Better assignment error messages (#146)


v2.7.0 (8 July 2015; first independent release)
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First release
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* Previously included as part of Stan
* Release numbering started at release number of Stan
* All work done up to and including the release of Stan Math 2.7.0
  is documented under the Stan C++ 2.7.0 release notes
