// *****************************************************************************
// *****************************************************************************
void Euler2D_Mesh::Tag_Boundary_Nodes() {
    int i, n1, n2, bctype, ibn;
    List bnode;

    // Tag the Boundary Nodes Points
    // Method of Tagging is not robust as boundary connecting points have Tag
    // which are tagged last.
    BNTag = (int *) calloc(mesh.nnodes, sizeof (int));
    for (i = 0; i < mesh.nnodes; i++)
        BNTag[i] = -1;

    for (i = 0; i < mesh.nbedges; i++) {
        n1 = edge[boundaryEdge[i].edgeNumber].node1;
        n2 = edge[boundaryEdge[i].edgeNumber].node2;
        bctype = -1;
        // BCType 0: 0-999
        if ((boundaryEdge[i].bcType >= 0) && (boundaryEdge[i].bcType <= 999))
            bctype = 0;
        // BCType 1: 1000-1999 : Solid Wall
        if ((boundaryEdge[i].bcType >= 1000) && (boundaryEdge[i].bcType <= 1999))
            bctype = 1;
        // BCType 2: 2000-2999 : Dirchlet Boundary Condition
        if ((boundaryEdge[i].bcType >= 2000) && (boundaryEdge[i].bcType <= 2999))
            bctype = 2;
        // BCType 2: 3000-3999 : Freestream
        if ((boundaryEdge[i].bcType >= 3000) && (boundaryEdge[i].bcType <= 3999))
            bctype = 3;

        if (bctype != -1) {
            BNTag[n1] = bctype;
            BNTag[n2] = bctype;
        }
    }

    mesh.nbnodes = 0;
    for (i = 0; i < mesh.nnodes; i++) {
        if (BNTag[i] != -1)
            mesh.nbnodes++;
    }

#ifdef VERBOSE
    info("NBNodes = %d", mesh.nbnodes);
#endif
    
    boundaryNode = (BOUNDARYNODE *) calloc(mesh.nbnodes, sizeof (BOUNDARYNODE));
    ibn = 0;
    for (i = 0; i < mesh.nbedges; i++) {
        n1 = edge[boundaryEdge[i].edgeNumber].node1;
        n2 = edge[boundaryEdge[i].edgeNumber].node2;

        // BCType 0: 0-999
        if ((boundaryEdge[i].bcType >= 0) && (boundaryEdge[i].bcType <= 999)) {
            if (!bnode.Is_In_List(n1)) {
                bnode.Add_To_List(n1);
                boundaryNode[ibn].bcType     = BNTag[n1];
                boundaryNode[ibn].nodeNumber = n1;
                boundaryNode[ibn].constant   = 0.0;
                ibn++;
            }
            if (!bnode.Is_In_List(n2)) {
                bnode.Add_To_List(n2);
                boundaryNode[ibn].bcType     = BNTag[n2];
                boundaryNode[ibn].nodeNumber = n2;
                boundaryNode[ibn].constant   = 0.0;
                ibn++;
            }
        }
        // BCType 1: 1000-1999 : Solid Wall
        if ((boundaryEdge[i].bcType >= 1000) && (boundaryEdge[i].bcType <= 1999)) {
            if (!bnode.Is_In_List(n1)) {
                bnode.Add_To_List(n1);
                boundaryNode[ibn].bcType     = BNTag[n1];
                boundaryNode[ibn].nodeNumber = n1;
                boundaryNode[ibn].constant   = 0.0;
                ibn++;
            }
            if (!bnode.Is_In_List(n2)) {
                bnode.Add_To_List(n2);
                boundaryNode[ibn].bcType     = BNTag[n2];
                boundaryNode[ibn].nodeNumber = n2;
                boundaryNode[ibn].constant   = 0.0;
                ibn++;
            }
        }
        // BCType 2: 2000-2999 : Dirchlet Boundary Condition
        if ((boundaryEdge[i].bcType >= 2000) && (boundaryEdge[i].bcType <= 2999)) {
            if (BNTag[n1] != 2) {
                if (!bnode.Is_In_List(n1)) {
                    bnode.Add_To_List(n1);
                    boundaryNode[ibn].bcType     = BNTag[n1];
                    boundaryNode[ibn].nodeNumber = n1;
                    if (boundaryEdge[i].bcType == 2000) {
                        boundaryNode[ibn].constant = node[n1].x;
                    } else {
                        boundaryNode[ibn].constant = boundaryEdge[i].c1;
                    }
                    ibn++;
                }
            }
            if (BNTag[n2] != 2) {
                if (!bnode.Is_In_List(n2)) {
                    bnode.Add_To_List(n2);
                    boundaryNode[ibn].bcType     = BNTag[n2];
                    boundaryNode[ibn].nodeNumber = n2;
                    if (boundaryEdge[i].bcType == 2000) {
                        boundaryNode[ibn].constant = node[n2].x;
                    } else {
                        boundaryNode[ibn].constant = boundaryEdge[i].c1;
                    }
                    ibn++;
                }
            }
        }
        // BCType 2: 3000-3999 : Freestream
        if ((boundaryEdge[i].bcType >= 3000) && (boundaryEdge[i].bcType <= 3999)) {
            if (!bnode.Is_In_List(n1)) {
                bnode.Add_To_List(n1);
                boundaryNode[ibn].bcType     = BNTag[n1];
                boundaryNode[ibn].nodeNumber = n1;
                boundaryNode[ibn].constant   = 0.0;
                ibn++;
            }
            if (!bnode.Is_In_List(n2)) {
                bnode.Add_To_List(n2);
                boundaryNode[ibn].bcType     = BNTag[n2];
                boundaryNode[ibn].nodeNumber = n2;
                boundaryNode[ibn].constant   = 0.0;
                ibn++;
            }
        }
    }
}