An unhandled exception of type 'System.StackOverflowException' occurred in mscorlib.dll during calling recursive function

Question

// code execute infinite and giving me error as unhanded exception of type 'System.StackOverflowException////

//default declaration //

Hashtable ht = new Hashtable(); // for store pagerank during recursion i have used hash table
DBML.Dbml_UploadDataContext objdbcontext = new DBML.Dbml_UploadDataContext(TDBConvertion.Properties.Settings.Default.MY_DBConnectionString); // this is DataContext of my DBML  and all tables have primary key and foreign key in it.

//method for calling recursive function //

 public string calculatepagerank()
        {
            double damp = 0.85;
           double output=0;

                objdbcontext.Connection.Open();
                string stroutput = "";

               foreach (var item in objdbcontext.Engine_Directories) // for all ids i want to calculate pr
                    {

                        output = pagerank(item.ID, objdbcontext.Engine_Links_Inlinks.Where(w => w.LinkID == item.ID).ToList(), objdbcontext.Engine_linkcounts.Where(x => x.ID == item.ID).FirstOrDefault().OutLinks.Value,damp);
                        stroutput = stroutput + ",Iteration::" + i + ",ID=" + item.ID + ",pagerank=" + output.ToString() + "\n";
                    }
                    ht.Clear();
                objdbcontext.Connection.Close();
            return stroutput;
        }

/// recursive function //

        public double pagerank(Int64 intId,List<DBML.Engine_Links_Inlink> listInlinksID,Int64 intoutlinkcount,double dumpingfactor)
        {

            double count = 0;
            double o = 0;

            foreach(var item in listInlinksID)
            {
                Int64 outlinkcount=1;
                if( objdbcontext.Engine_linkcounts.Where(x => x.ID == item.InlinksID).FirstOrDefault()!=null)
                {
                    Int64 outc = objdbcontext.Engine_linkcounts.Where(x => x.ID == item.InlinksID).FirstOrDefault().OutLinks.Value;
                    outlinkcount=( outc !=0)?outc:1 ;
                }

                if (!ht.ContainsKey(item.InlinksID))
                {
                    o = pagerank(item.InlinksID.Value,objdbcontext.Engine_Links_Inlinks.Where(w => w.LinkID == item.InlinksID).ToList(), outlinkcount, dumpingfactor);

                    ht.Add(item.InlinksID.Value, o);
                    count = count + o;
                }
                else
                {
                    count = count + Convert.ToDouble(ht[item.InlinksID].ToString());
                }

            }          
            return dumpingfactor + dumpingfactor * (count/intoutlinkcount);
        }

Answer 1

Well .NET have not infinity-size stack. By default it's 1MB only. Execute this code in new thread with larger stack size(second argument for "Thread" constructor), or use loops instead of recursion.

Answer 2

Could you possibly refactor the following piece of code?

if (!ht.ContainsKey(item.InlinksID))
{
   o = pagerank(item.InlinksID.Value,objdbcontext.Engine_Links_Inlinks.Where(w => w.LinkID == item.InlinksID).ToList(), outlinkcount, dumpingfactor);

   ht.Add(item.InlinksID.Value, o);
   count = count + o;
}

Instead of recursively calling pagerank, why don't you do take the code and add use coroutines ?