I am an idiot ;-))))
I had used Eclipse's recover a deleted method utility and brought back an
old version of test() that had additional calls to hashCode() in it. It was
no wonder that it was slower. When I made it have the same code it gave the
same results....
Apologies for my input, and thanks for the input anyway.
Stephen
----- Original Message -----
From: "Tim Funk" <[EMAIL PROTECTED]>
> Could the compiler being doing some optimization?
>
> Version 1: The compiler might be able to infer that a HashMap is being
> used so it doesn't need a late-binding lookup on Map.
>
> Version 2: The late-binding lookup is needed since a Map is passed into
> the method.
>
> What happens if test(Map map) changes to test(HashMap map) for your test?
>
> -Tim
>
>
> [EMAIL PROTECTED] wrote:
> >> from: "Shapira, Yoav" <[EMAIL PROTECTED]>
> >>
> >>>Test class #2)
> >>>public static void main(String[] args) {
> >>> Map map = new HashMap();
> >>> map.put("AAA");
> >>> map.put("BBB");
> >>> map.put("CCC");
> >>>
> >>> test(map);
> >>>}
> >>>private static void test(Map map) {
> >>> long start = 0;
> >>> long end = 0;
> >>>
> >>> start = System.currentTimeMillis();
> >>> for (int i = RUNS; i >= 0; i--) {
> >>> map.get("AAA");
> >>> map.get("BBB");
> >>> map.get("CCC");
> >>> }
> >>> end = System.currentTimeMillis();
> >>> System.out.println(end - start);
> >>>}
> >>>
> >>>These two classes give very different results. The refactored version
> >>
> >>#2 is
> >>
> >>>much slower, between 20% and 80% depending on the type of Map.
> >>>
> >>>Am I missing something obvious???
> >>>[Sun JDK 1.4.1_01 (client or server)]
> >>
> >>I don't think you're missing something obvious. But out of curiosity,
> >>if you mark the test(Map) method final, does the performance come out
> >>equal to version #1 of your class? It should, as the 1.4.1 compiler
> >>will inline the method.
> >>
> >>Also, does the 20% difference reduce when you increase RUNS? If RUNS is
> >>a very small value, then the method invocation overhead can actually be
> >>pretty high when compared to the run itself. Make RUNS 100000 and
> >>measure the difference between the classes again, if you haven't done so
> >>already...
> >
> >
> > The value I'm using for RUNS is 10,000,000, giving total time of the
order of 2-7 seconds for each loop.
> >
> > Also, if you look at the code, the measurement (start to end) is all
within the test(Map) method and doesn't include method invocations. Thats
whats so strange...
> >
> > Stephen
> >
>
>
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