Refactor: move Model::state_ initalization to ModelState ctor (AMICI-…

…dev#2533)

Move `Model::state_` initalization to `ModelState` ctor where it belongs.

Closes AMICI-dev#2531.

include/amici/model_state.h

@@ -18,6 +18,19 @@ namespace amici {
  * number of attributes that need to be transferred.
  */
 struct ModelState {
+    ModelState() = default;
+    /**
+     * @brief Constructor from model dimensions.
+     * @param dim Model dimensions
+     */
+    explicit ModelState(ModelDimensions const& dim) {
+        h.resize(dim.ne, 0.0);
+        total_cl.resize(dim.nx_rdata - dim.nx_solver, 0.0);
+        stotal_cl.resize((dim.nx_rdata - dim.nx_solver) * dim.np, 0.0);
+        unscaledParameters.resize(dim.np);
+        fixedParameters.resize(dim.nk);
+    }
+
     /**
      * Flag indicating whether a certain Heaviside function should be active or
      * not (dimension: `ne`)

src/model.cpp

@@ -183,7 +183,8 @@ Model::Model(
     , o2mode(o2mode)
     , idlist(std::move(idlist))
     , state_independent_events_(std::move(state_independent_events))
-    , derived_state_(model_dimensions)
+    , state_(*this)
+    , derived_state_(*this)
     , z2event_(std::move(z2event))
     , state_is_non_negative_(nx_solver, false)
     , simulation_parameters_(std::move(simulation_parameters)) {
@@ -200,10 +201,6 @@ Model::Model(
         model_dimensions.np, ParameterScaling::none
     );
 
-    state_.h.resize(ne, 0.0);
-    state_.total_cl.resize(nx_rdata - nx_solver, 0.0);
-    state_.stotal_cl.resize((nx_rdata - nx_solver) * np(), 0.0);
-    state_.unscaledParameters.resize(np());
     unscaleParameters(
         simulation_parameters_.parameters, simulation_parameters_.pscale,
         state_.unscaledParameters