[Mono-bugs] [Bug 59537][Nor] Changed - improve NameTable performance

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Changed by atsushi@ximian.com.

http://bugzilla.ximian.com/show_bug.cgi?id=59537

--- shadow/59537	2004-06-06 10:12:08.000000000 -0400
+++ shadow/59537.tmp.27631	2004-06-06 10:52:50.000000000 -0400
@@ -90,6 +90,111 @@
 someone will overload the Add with StringBuilder parameter?) . In
 order to make the code resilient I think we should pay the performance
 "fee" and perform a delegation to one ImplMethod. Afterall , the real
 performance problems are not here, they are in System.Data (this is
 why I rated the issue NORMAL and not CRITICAL)
 
+
+------- Additional Comments From atsushi@ximian.com  2004-06-06 10:52 -------
+I have three points to say.
+
+1) Again, we need concrete performance comparison data such as  shown
+below.
+2) Our GC is convervative so that avoiding object creation is 
+   much important than MS.NET that has generational GC.
+3) You should not set CRITICAL priority without reading what
+"priority" means. It is written in the page linked from the immediate
+side of the select box, no matter how big the performance difference is.
+
+
+// net nametable implementation
+using System;
+using System.Collections;
+namespace System.Xml
+{
+	public class NameTable : XmlNameTable
+	{
+		Hashtable table = new Hashtable ();
+
+		public NameTable () {}
+
+		public override string Add (string name)
+		{
+			int hash = name.GetHashCode ();
+			string ret = (string) table [hash];
+			if (ret != null)
+				return ret;
+			table [hash] = name;
+			return name;
+		}
+
+		public override string Add (char [] name, int start, int len)
+		{
+			return Add (new string (name, start, len));
+		}
+
+		public override string Get (string name)
+		{
+			int hash = name.GetHashCode ();
+			return (string) table [hash];
+		}
+
+		public override string Get (char [] name, int start, int len)
+		{
+			return Get (new string (name, start, len));
+		}
+	}
+}
+
+// comparison code
+
+using System;
+using System.Xml;
+
+public class Test
+{
+  public static void Main ()
+  {
+    long start = DateTime.Now.Ticks;
+    NameTable nt = new NameTable ();
+    char [] name = new char [] {'n', 'a', 'm', 'e', '0', '0', '0',
+'0', '0'};
+    AddBatch (nt, name);
+    AddBatch (nt, name);
+    Console.WriteLine (DateTime.Now.Ticks - start);
+  }
+
+  private static void AddBatch (NameTable nt, char [] name)
+  {
+    for (int i = 0x30; i < 0x3A; i++) {
+      name [4] = (char) i;
+      for (int j = 0x30; j < 0x3A; j++) {
+        name [5] = (char) j;
+        for (int k = 0x30; k < 0x3A; k++) {
+          name [6] = (char) k;
+          for (int l = 0x30; l < 0x3A; l++) {
+            name [7] = (char) l;
+            for (int m = 0x30; m < 0x3A; m++) {
+              name [8] = (char) m;
+              nt.Add (name, 0, 9);
+            }
+          }
+        }
+      }
+    }
+  }
+}
+
+// The result with new code:
+12020000
+Total time spent compiling 602 methods (sec): 0.07
+Slowest method to compile (sec): 0.01: System.Xml.XmlNameTable::.ctor()
+
+Total memory allocated: 13530 KB
+
+// The result with existing code:
+4810000
+Total time spent compiling 604 methods (sec): 0.1
+Slowest method to compile (sec): 0.01: System.DateTime::GetNow()
+
+Total memory allocated: 6880 KB
+