add dahlquist

Author: markaren

examples/CMakeLists.txt

@@ -6,3 +6,4 @@ add_subdirectory(VanDerPol)
 add_subdirectory(ExternalSharedLib)
 add_subdirectory(ExternalInterfaceLib)
 add_subdirectory(Identity)
+add_subdirectory(Dahlquist)

examples/Dahlquist/CMakeLists.txt

@@ -0,0 +1,8 @@
+
+generateFMU("Dahlquist"
+        SOURCES
+        "dahlquist.cpp"
+        FMI_VERSIONS
+        "fmi2;fmi3"
+        WITH_SOURCES
+)

examples/Dahlquist/dahlquist.cpp

@@ -0,0 +1,60 @@
+
+#include "fmu4cpp/fmu_base.hpp"
+
+#include <cmath>
+
+class Dahlquist : public fmu4cpp::fmu_base {
+
+public:
+    FMU4CPP_CTOR(Dahlquist) {
+
+        register_variable(real("x", &x)
+                                  .setCausality(fmu4cpp::causality_t::OUTPUT)
+                                  .setVariability(fmu4cpp::variability_t::CONTINUOUS)
+                                  .setInitial(fmu4cpp::initial_t::EXACT));
+
+        register_variable(real("dx", &dx)
+                                  .setCausality(fmu4cpp::causality_t::LOCAL)
+                                  .setVariability(fmu4cpp::variability_t::CONTINUOUS));
+
+        register_variable(real("k", &k)
+                                  .setCausality(fmu4cpp::causality_t::PARAMETER)
+                                  .setVariability(fmu4cpp::variability_t::FIXED));
+
+        Dahlquist::reset();
+    }
+
+    bool do_step(double dt) override {
+
+        const double lambda = k;
+        // exact Dahlquist step: x_{n+1} = exp(lambda * dt) * x_n
+        double x_new = std::exp(lambda * dt) * x;
+        // derivative at the new state
+        dx = lambda * x_new;
+        x = x_new;
+
+        return true;
+    }
+
+
+    void reset() override {
+        x = 1.0;
+        dx = 0.0;
+        k = -1.0;
+    }
+
+private:
+    double x{};
+    double dx{};
+    double k{};
+};
+
+fmu4cpp::model_info fmu4cpp::get_model_info() {
+    model_info info;
+    info.modelName = "Dahlquist";
+    info.description = "This model implements the Dahlquist test equation";
+    info.defaultExperiment = {0, 10, 0.1};
+    return info;
+}
+
+FMU4CPP_INSTANTIATE(Dahlquist);