Re: Small patch for loop macro

> If you just have one string to output, it doesn't make much of a
> difference, since the Helma Skin class will just do the res.write()
> for you. If, on the other hand, your macro output is composed of many
> small pieces, it's better to directly use res.write(), since
> composing a string with multiple + concatenations adds a lot of
> memory overhead (each + operation results in the whole string being
> reallocated in memory).      

which is, btw., not true anymore in browsers (esp. firefox). i once benchmarked the various methods (see below) and found that only helma/rhino behaves pretty badly when concatenating strings via the "+" operator.

the methods i checked:

 * String assignment: str = str + "foo"
 * String.concat: String.concat(str, "foo") // if available
 * Array assignment: arr[arr.length] = str
 * Array.push: arr.push(str)

here's a typical result creating strings with 50.000 chars as an example (the first values represent the duration in milliseconds, the string lengths appear in brackets):

Browser (IE)
String assignment: 1031 (50000)
Array assignment: 406 (50000)
Array.push: 547 (50000)

Server
String assignment: 6256 (50000)
Array assignment: 112 (50000)
Array.push: 133 (50000)

--

Browser (Moz)
String assignment: 47 (50000)
String.concat: 797 (50000)
Array assignment: 172 (50000)
Array.push: 203 (50000)

Server
String assignment: 6388 (50000)
Array assignment: 337 (50000)
Array.push: 249 (50000)


(i attached the source code of the benchmark test to this message -- hope it gets through our firewall :)

i am still wonderung what could be the reason that the string concatenation operator performs so differently in helma/rhino?

ciao,
tobi

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var str_benchmark = function() {
   var benchmark = function() {
      var log = function(str) {
         str += "<br />";
         (typeof res === "undefined") ? document.writeln(str) : res.writeln(str$
      };

      var MAX = 50000;
      var start, str, arr;

      start = new Date;
      str = "";
      for (var i=0; i<MAX; i+=1) {
         str = str + "x";
      }
      log("String assignment: " + (new Date - start) + " (" + str.length + ")");

      if (String.concat) {
         start = new Date;
         str = "";
         for (var i=0; i<MAX; i+=1) {
            str = String.concat(str, "x");
         }
         log("String.concat: " + (new Date - start) + " (" + str.length + ")");
      }

      start = new Date;
      arr = [];
      for (var i=0; i<MAX; i+=1) {
         arr[arr.length] = "x";
      }
      arr.join();
      log("Array assignment: " + (new Date - start) + " (" + arr.length + ")");

      start = new Date;
      arr = [];
      for (var i=0; i<MAX; i+=1) {
         arr.push("x");
      }
      arr.join();
      log("Array.push: " + (new Date - start) + " (" + arr.length + ")");
      return;
   };

   res.writeln("<h4>Browser</h4>");
   res.writeln("<script>");
   res.write("var benchmark = ");
   res.writeln(benchmark.toSource() + ";");
   res.writeln("benchmark();");
   res.writeln("</script>");
   res.writeln("<h4>Server</h4>");
   benchmark();
   return;
};