NEWS.md
Added Model::likelihood_total_grad() and Model::likelihood_total_hess() for the exact gradient and Hessian of the total log-likelihood, and Model::likelihood_total_and_grad() to compute the log-likelihood and gradient together. The Hessian is returned as a row-major vector. These methods use numerically stable, max-shifted exponentials and do not modify the model or its cached normalizing constants (USCbiostats/barry#27).
Fixed defm_motif_parser reading covariate names as motif terms: a formula such as {y0} > {y0} x Day1 silently added y1 to the motif. Variables are now only read from the bracketed groups. Also fixed {...}x Covar (no space before x) silently dropping the covariate, transitions accepting current-time rows on the LHS (e.g., {y0_1} > {y1}), and unchecked out-of-range rows with Markov order 1 (USCbiostats/barry#26).
Fixed support-vs-array index confusion in Model::sample and DEFM::simulate, which produced wrong draws when simulating (USCbiostats/barry#25).
Fixed catastrophic hash collisions in FreqTable::make_hash and vecHasher: hashes of small-integer statistics had no entropy in their low bits, so std::unordered_map placed (nearly) all keys in a single bucket, making support computation O(4^ncol) instead of O(2^ncol). Models with many response columns (e.g., 16) appeared to hang during initialization (USCbiostats/barry#24).
FreqTable::add() now verifies the stored row on a hash hit and keeps true 64-bit hash collisions in a per-hash overflow chain, so distinct statistics can no longer be silently merged (USCbiostats/barry#24).