v.2.18.0 (13 July 2018)

This is our first release with parallelism (through C++11 threads or MPI)!

New Features

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)

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)