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

Chris Hegarty chris.hegarty at oracle.com
Thu May 14 07:58:52 UTC 2015

On 14 May 2015, at 03:24, Martin Buchholz <martinrb at google.com> wrote:

> Your changes look good,

Yes, this is a nice improvement.

> but:
> 204             check(map.size() == i, "insertion: map expected size
> m%d != i%d", map.size(), i);
> many of those detail messages look like leftovers from a long debugging
> session.  Here I would consider converting to a testng test (I ended up
> doing this a few times myself) and writing very simply, standardly,
> efficiently and readably
> assertEquals(map.size(), i);

Or could use jdk.testlibrary.Asserts.assertEquals, if you want to avoid spinning up the testng machinery, and generating yet another xml test report. If you are only interested in assertEquals.

> only adding more breadcrumbs if it's non-obvious, which is generally not
> the case in this test.

Either if ok with me.

> testMap already prints out keys_desc, so the test output is unambiguous.
> On Wed, May 13, 2015 at 6:44 PM, Stuart Marks <stuart.marks at oracle.com>
> 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’ve used the varargs version a number of times in my own tests. It is simple and easy to read. But if this 15% is important, then it could be worth the extra overloads.  Either way I’m happy to this this change going in.


>> Thanks.
>> s'marks

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