Fixed crash when using face meshes and element IDs don't start to 0

adapter/CCXHelpers.h

@@ -53,6 +53,17 @@ enum CouplingDataType { TEMPERATURE,
                         VELOCITIES,
                         POSITIONS };
 
+/**
+ * @brief Type of element used for faces mesh, where we assume only one type of element is used.
+ *  TETRAHEDRA      - C3D4 or C3D10 element
+ *  HEXAEDRA        - C3D8 or C3D20 elment
+ *  INVALID_ELEMENT - Anything else
+ */
+enum ElemType { TETRAHEDRA,
+                HEXAEDRA,
+                INVALID_ELEMENT,
+};
+
 /**
  * @brief Returns node set name with internal CalculiX format
  * Prepends and appends an N: e.g. If the input name is "interface",

adapter/PreciceInterface.c

@@ -486,9 +486,28 @@ void PreciceInterface_Create(PreciceInterface *interface, SimulationData *sim, I
   PreciceInterface_ConfigureCouplingData(interface, sim, config);
 }
 
+static enum ElemType findSimulationMeshType(SimulationData *sim)
+{
+  // Assuming only tetrahedra are used, or only hexaedral, for faces meshes.
+  // Return first non-zero mesh type.
+  // lakon tab takes 8 chars per element
+
+  const char *lakon_ptr = sim->lakon;
+  for (int i = 0; i < sim->ne; ++i) {
+    if (startsWith(lakon_ptr, "C3D4") || startsWith(lakon_ptr, "C3D10")) {
+      return TETRAHEDRA;
+    } else if (startsWith(lakon_ptr, "C3D8") || startsWith(lakon_ptr, "C3D20")) {
+      return HEXAEDRA;
+    }
+    lakon_ptr += 8;
+  }
+
+  return INVALID_ELEMENT;
+}
+
 void PreciceInterface_ConfigureFaceCentersMesh(PreciceInterface *interface, SimulationData *sim)
 {
-  //printf("Entering ConfigureFaceCentersMesh \n");
+  // printf("Entering ConfigureFaceCentersMesh \n");
   char *faceSetName      = toFaceSetName(interface->name);
   interface->faceSetID   = getSetID(faceSetName, sim->set, sim->nset);
   interface->numElements = getNumSetElements(interface->faceSetID, sim->istartset, sim->iendset);
@@ -499,9 +518,14 @@ void PreciceInterface_ConfigureFaceCentersMesh(PreciceInterface *interface, Simu
 
   interface->faceCenterCoordinates = malloc(interface->numElements * 3 * sizeof(double));
   interface->preciceFaceCenterIDs  = malloc(interface->numElements * 3 * sizeof(int));
-  if (startsWith(&sim->lakon[1 * 8], "C3D4") || startsWith(&sim->lakon[1 * 8], "C3D10")) {
+
+  enum ElemType elemType = findSimulationMeshType(sim);
+
+  if (elemType == TETRAHEDRA) {
+    printf("Configuring faces mesh with tetrahedra.\n");
     getTetraFaceCenters(interface->elementIDs, interface->faceIDs, interface->numElements, sim->kon, sim->ipkon, sim->co, interface->faceCenterCoordinates);
-  } else if (startsWith(&sim->lakon[1 * 8], "C3D8") || startsWith(&sim->lakon[1 * 8], "C3D20")) {
+  } else if (elemType == HEXAEDRA) {
+    printf("Configuring faces mesh with hexahedra.\n");
     getHexaFaceCenters(interface->elementIDs, interface->faceIDs, interface->numElements, sim->kon, sim->ipkon, sim->co, interface->faceCenterCoordinates);
   } else {
     supportedElementError();

adapter/PreciceInterface.h

@@ -113,6 +113,7 @@ typedef struct SimulationData {
   int     nload;
   char *  sideload;
   double  nk;
+  ITG     ne;
   ITG     mt;
   double *theta;
   double *dtheta;

dyna_precice.c

@@ -230,6 +230,7 @@ void dyna_precice(double **cop, ITG *nk, ITG **konp, ITG **ipkonp, char **lakonp
       .sideload  = sideload,
       .mt        = mt,
       .nk        = *nk,
+      .ne        = *ne,
       .theta     = &theta,
       .dtheta    = &dtheta,
       .tper      = tper,

nonlingeo_precice.c

@@ -329,6 +329,7 @@ void nonlingeo_precice(double **cop, ITG *nk, ITG **konp, ITG **ipkonp, char **l
       .sideload  = sideload,
       .mt        = mt,
       .nk        = *nk,
+      .ne        = *ne,
       .theta     = &theta,
       .dtheta    = &dtheta,
       .tper      = tper,