feat: expose accessor functions for control parameters (#296)

Fixes #295
climateinteractive · Dec 9, 2022 · a44d097 · a44d097
1 parent ba510b0
commit a44d097
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Showing 2 changed files with 57 additions and 2 deletions.
diff --git a/packages/cli/src/c/sde.h b/packages/cli/src/c/sde.h
@@ -50,15 +50,20 @@ EXTERN double _final_time;
 EXTERN double _time_step;
 EXTERN double _saveper;
 
-// API
+// API (defined in model.h)
 char* run_model(const char* inputs);
 void runModelWithBuffers(double* inputs, double* outputs);
 void run(void);
 void startOutput(void);
 void outputVar(double value);
 void finish(void);
 
-// Functions implemented by the model
+// API (defined by the generated model)
+double getInitialTime(void);
+double getFinalTime(void);
+double getSaveper(void);
+
+// Functions implemented by the generated model
 void initConstants(void);
 void initLevels(void);
 void setInputs(const char* inputData);

diff --git a/packages/compile/src/generate/code-gen.js b/packages/compile/src/generate/code-gen.js
@@ -42,6 +42,7 @@ let codeGenerator = (parseTree, opts) => {
       } else if (operation === 'generateC') {
         // Generate code for each variable in the proper order.
         let code = emitDeclCode()
+        code += emitGetControlValuesCode()
         code += emitInitLookupsCode()
         code += emitInitConstantsCode()
         code += emitInitLevelsCode()
@@ -79,6 +80,55 @@ ${dimensionMappingsSection()}
 ${section(Model.lookupVars())}
 ${section(Model.dataVars())}
 
+`
+  }
+
+  //
+  // Control value getters section
+  //
+  function emitGetControlValuesCode() {
+    function getConstTimeValue(vensimName) {
+      const v = Model.varWithName(Model.cName(vensimName))
+      if (v && v.varType === 'const') {
+        return v.modelFormula
+      } else {
+        throw new Error(`SDE only supports ${vensimName} defined as a constant value`)
+      }
+    }
+
+    function getSaveperValue() {
+      const v = Model.varWithName('_saveper')
+      if (v && v.varType === 'const') {
+        return v.modelFormula
+      } else if (v && v.varType === 'aux' && v.modelFormula === 'TIME STEP') {
+        return getConstTimeValue('TIME STEP')
+      } else {
+        throw new Error(`SDE only supports SAVEPER defined as TIME STEP or a constant value`)
+      }
+    }
+
+    // For now we only allow models that have:
+    //   INITIAL TIME = a constant value
+    //   FINAL TIME = a constant value
+    //   SAVEPER = a constant value or constant `TIME STEP`
+    // If the model does not meet these expectations, we throw an error.
+    // TODO: Loosen this up to allow for certain common constant expressions
+    const initialTimeValue = getConstTimeValue('INITIAL TIME')
+    const finalTimeValue = getConstTimeValue('FINAL TIME')
+    const saveperValue = getSaveperValue('SAVEPER')
+
+    return `
+// Control parameter accessors
+double getInitialTime() {
+  return ${initialTimeValue};
+}
+double getFinalTime() {
+  return ${finalTimeValue};
+}
+double getSaveper() {
+  return ${saveperValue};
+}
+
 `
   }