• More gracefully cope with filenames containing parentheses
• Added JavaScript support, importing code previously in odin.js. Models with delays are not supported (mrc-1624)
• Optimise some if/else statements where the condition can be worked out at compile time; this means only one clause may be present in the generated code (mrc-2529)
• Deprecate the function-style constructors (e.g., generator(...)) in favour of R6-style constructors (generator$new(...)) (#206) • Allow spaces in filenames passed to odin::odin() (#225) • New option rewrite_constants (via odin::odin_options) which attempts to rewrite all constants in the model code before generation. This can considerably reduce the number of variable lookups (mrc-2252) • New option substitutions (via odin::odin_options) which can substitute in scalar user values at compile time (#220) • New option rewrite_dims (via odin::odin_options) which will attempt to simplify common dimensions. This can reduce the number of variables carried around in the model as these are typically very redundant and also known at compile time (mrc-2093) • Annotate equations with # ignore.unused to locally suppress messages about unused variables (mrc-2122) • odin no longer warns about use of index variables on rhs as new behaviour has been established for a while (#136) • Support for config(include) has been expanded, working for R models and designed to be extensible for other targets (mrc-2016) • The basic infrastructure has been overhauled, which will make some alternative compilation targets easier to support. We now use pkgbuild for the compilation which should ease debugging, and odin code compiled into packages will no longer issue a slew of warnings (and cooperate with automatic routine registration). This refactor has caused a few minor breaking changes: • $initial() always requires time, even if it is ignored
• $set_user() and construction no longer work with positional argument matching - all arguments must be named • The $ir field has become a method; add parentheses after it
• The compiler_warnings option has been removed
• Support for as.integer() to cast to integer for use within array expressions (#200)
• Fixed bug in code generation for initial conditions involving sums of matrices (#196)
• Support for multivariate hypergeometric function via the odin function rmhyper() - there is no analogue for this in base R. Like rmultinom this returns a vector and the interface is subject to possible change (mrc-1621)
• New vignette functions, which briefly describes all supported odin functions (mrc-1623)
• Support for 2-argument round (e.g., round(1.23, 1) is 1.2), and enforce the same 0.5 rounding behaviour as R when used from C (mrc-511, #116, #179)
• Initial release to CRAN
• Default history size is back to 10,000 steps (not 1,000) as in pre-0.2.0 (mrc-327, #176)
• odin_package now works with R staged installation as introduced in 3.6.0 (#170, mrc-257)
• Better error messages for some invalid uses of array indices that previously manifested as compiler errors #166
• Fix two memory leaks (#163); these leaked once per model creation.
• Continuous time models with delays can now return derivatives (#161, #162)

A complete rewrite of the odin engine, designed to increase future maintainability but have few user-visible effects. In brief, this does add

• Ability to transpile to R (removing the need for a C compiler, though creating code that is necessarily much slower than the compiled version). Pass target = "r" to use this.
• A new intermediate representation for odin models that can be used to determine features of a model
• Better caching (#64)
• Delays on discrete time models are much more efficient and work properly with stochastic equations (#72, #98)

This does introduce a few user-visible breaking changes: - use of array indices outside of an array subset (e.g., x[] <- i) produces output that is off-by-one compared with the previous version (see #136) - The “safe” mode has been removed, at least for now. This failed to compile for complex models and was not well used. A better static check mechanism will be introduced (#148) - Arguments to odin() have been modified slightly - odin_package() no longer supports multi-file mode (I don’t think this was ever used). - Argument order in generated functions, as well as variable/output order, is likely to change but this should not generally be relied upon. - The methods for a model object have been extensively rationalised. I don’t think that anything has been removed that anyone is using in their code. - The parameters passed as a list user are validated and providing additional parameters is a warning (by default; this can be configured to be more or less strict as desired).

Fixes many outstanding issues: #139, #136, #132, #130, #129, #127, #123, #122, #121, #120, #117, #115, #112, #106, #99, #98, #84, #72, #64, #57, #52, #12, #4

• Validate parameters in input
• Replication interface for discrete models (primarily for stochastic models) #125.
• Delay differential equations may use interpolated functions within their delays #130
• Fix caching of models specified with files (rather than inline code) #99
• Support for multinomial distributions, which are the first example of supported vector-returning functions #100
• New vignette for discrete time models, contributed by @thibautjombart #102
• Generate odin models in “safe” mode, where all array access is bounds-checked. This will run slower but make debugging crashes much simpler (#79, #49)
• Implement caching layer #54 and possibly enough for #62. The interface here is subject to change (currently there is no way to interact with the cache) but should be enough for most cases. Setting the output directory explicitly will be necessary to cache across sessions.