ElementConnectivityx.cpp

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#include "./ElementConnectivityx.h"
 
#include "../../shared/shared.h"
#include "../../toolkits/toolkits.h"
 
int hascommondedge(int* element1,int* element2);
 
void ElementConnectivityx(int** pelementconnectivity,int* elements, int nels,int* nodeconnectivity, int nods, int width){
 
   int i,j,k,n;
 
   /*intermediary: */
   int    maxels;
   int  connectedelement;
   int    connectedelementindex;
   int    node;
   int    index;
   int    num_elements;
 
   /*maxels: */
   maxels=width-1;
 
   /*Allocate connectivity: */
   int* elementconnectivity=xNewZeroInit<int>(nels*3);
 
   /*Go through all elements, and for each element, go through its nodes, to get the neighbouring elements. 
    * Once we get the neighbouring elements, figure out if they share a segment with the current element. If so, 
    * plug them in the connectivity, unless they are already there.: */
   for(n=0;n<nels;n++){
 
      //element=n+1; //matlab indexing
 
      for(i=0;i<3;i++){
 
         node=elements[n*3+i]; //already matlab indexed, elements comes directly from the workspace.
         index=node-1;
 
         num_elements=nodeconnectivity[width*index+maxels]; //retrieve number of elements already  plugged into the connectivity of this node.
 
         for(j=0;j<num_elements;j++){
 
            /*for each element connected to node, figure out if it has a commond edge with element: */
            connectedelement=nodeconnectivity[width*index+j];
            connectedelementindex=connectedelement-1; //go from matlab indexing to c indexing.
 
            if(hascommondedge(&elements[n*3+0],&elements[connectedelementindex*3+0])){
               /*Ok, this connected element has a commond edge  with element, plug it into elementconnectivity, unless 
                *it is already there: */
 
               for(k=0;k<3;k++){
                  if(elementconnectivity[3*n+k]==0){
                     elementconnectivity[3*n+k]=connectedelement;
                     break;
                  }
                  else{
                     if(connectedelement==elementconnectivity[3*n+k]) break;
                  }
               }
            }
         }
      }
   }
 
   /*Assign output pointers: */
   *pelementconnectivity=elementconnectivity;
}
 
int hascommondedge(int* el1,int* el2){
 
   int count=0;
   for(int i=0;i<3;i++){
      for(int j=0;j<3;j++){
         if(el1[i]==el2[j]) count++;
      }
   }
   if(count==2)
    return 1;
   else
    return 0;
}