RFR: Here are some easy patches

[Michael Rasmussen]

Hi Martin,


Did you consider using Class::isArray in the loop? Something like the following:

for (Object element : a) {
  final int elementHash;
  if (element == null) {
    elementHash = 0;
  }
  else {
    final Class<?> cl = element.getClass();
    if (!cl.isArray())
      elementHash = element.hashCode();
    else if (element instanceof Object[])
      elementHash = deepHashCode((Object[]) element);
    else
      elementHash = primitiveArrayHashCode(element, cl.getComponentType());
  }

  result = 31 * result + elementHash;
}


In my quick JMH test running on Java 10, it improved the performance with your test array (Object[100000] full of Integers) from 244 us/op to 160 us/op (vs current JDK: 399 us/op).


/Michael

________________________________
From: core-libs-dev <core-libs-dev-bounces at openjdk.java.net> on behalf of Martin Buchholz <martinrb at google.com>
Sent: 02 May 2018 21:17:19
To: Paul Sandoz
Cc: core-libs-dev
Subject: Re: RFR: Here are some easy patches

Hi Paul,

On Mon, Apr 30, 2018 at 2:03 PM, Paul Sandoz <paul.sandoz at oracle.com> wrote:

>
>
> On Apr 30, 2018, at 11:18 AM, Martin Buchholz <martinrb at google.com> wrote:
>
>
>
> On Mon, Apr 30, 2018 at 10:35 AM, Paul Sandoz <paul.sandoz at oracle.com>
> wrote:
>
>> An obvious optimization:
>>
>> 8202398: Optimize Arrays.deepHashCode
>> http://cr.openjdk.java.net/~martin/webrevs/jdk/deepHashCode-optimize/
>> https://bugs.openjdk.java.net/browse/JDK-8202398
>>
>> I would prefer that the deeply nested ternary expressions be changed to a
>> more expected if/else if/else
>>
>
> My brain much prefers code transforming tabular data to "look tabular".
>
>
>
> I think you will like expression switch :-) in the interim i would stick
> with the less eyebrow raising syntax.
>
>
I'm going to claim committer's privilege and check in with my preferred
tabular style.  You can rewrite using suburban sprawl style when us
dinosaurs from the last milllenium have gone extinct.