RFR(s): 8078463: optimize java/util/Map/Collisions.java

[Daniel Fuchs]

Hi Stuart,

On 5/14/15 3:44 AM, Stuart Marks wrote:
> Hi all,
>
> Please review this change to optimize a test. Basically the test did 
> string formatting for every assertion, but the string was thrown away 
> if the assertion passed -- the most common case. The change is to do 
> the string formatting only when an assertion fails and information 
> needs to be printed out.
>
> Thanks to Andrey Zakharov for discovering and investigating this.
>
> Bug report:
>
>     https://bugs.openjdk.java.net/browse/JDK-8078463
>
> Webrev:
>
>     http://cr.openjdk.java.net/~smarks/reviews/8078463/webrev.0/
>
> On my (new, fast) laptop, with JVM options -Xcomp -XX:+DeoptimizeALot 
> -client, the unmodified test takes about 21.4 seconds to run. The 
> modified test takes only 12.3 seconds.
>
> Note that I have added several overloads of check() with different 
> arguments. I tried an alternative, which is a varargs version of check():
>
>     static void    check(boolean cond, String fmt,    Object... args) {
>         if (cond) {
>             pass();
>         } else {
>             fail(String.format(fmt, args));
>         }
>     }
>
> This of course is much simpler code, but it took 14.2 seconds, about 
> 15% slower than the proposed version. Is the simpler code worth the 
> slowdown? I could go either way.
I'm curious: have you tried with using a lambda instead? changing:

  394     static void check(String desc, boolean cond) {
  395         if (cond) {
  396             pass();
  397         } else {
  398             fail(desc);
  399         }
  400     }

into

static void check(Supplier<String> descSupplier, boolean cond) {
     if (cond) {
         pass();
     } else {
         fail(descSupplier.get())
     }
}

I wonder how the performance would compare...

best regards,

-- daniel
>
> Thanks.
>
> s'marks
>
>