                 Changes in version 2.1-0 (2026-09-11)                  

  - The C computational engine has been rewritten in Rcpp/RcppArmadillo,
    replacing the legacy .C() interface. qde() and qrjoint() now share a
    single underlying engine.
  - Fixed a bug in qrjoint() (not qde()) where observations with zero
    weight (wt = 0) could produce NaN in the log-posterior, potentially
    freezing the MCMC chain. Zero-weight observations now correctly
    contribute nothing to the likelihood, as documented. This has no
    effect on models fit with the default (all nonzero) weights.
  - Performance improvements, all exact (no change to the statistical
    model): Gaussian-process components are now cached and only
    recomputed for the MCMC blocks that actually change them; a
    redundant per-grid-point quantile-function evaluation in the base
    distribution is now computed once per log-posterior evaluation
    instead of once per grid point; and the per-observation
    quantile-bracket search now uses binary search instead of a linear
    scan. Combined, these give roughly a 1.7-1.9x speedup on typical
    problem sizes with identical statistical results.
  - Added a more numerically robust Cholesky factorization for the
    adaptive proposal covariance, with jitter-based recovery on failure
    instead of silently propagating NaN.
  - Updated the redmaple data source URL in the documentation.
