Java 9 and IntSummaryStatistics et al.

[Chris Dennis]

Taking from this conversation that there is consensus (at least amongst those on this thread) that this is an issue that should be fixed, what should my next steps be in order to help move this forward?

> On Mar 30, 2017, at 10:01 AM, Peter Levart <peter.levart at gmail.com> wrote:
> 
> 
> 
> On 03/30/2017 03:14 PM, Chris Dennis wrote:
>> This is indeed nice… but I presume that we all agree that the best solution here would be to allow instantiation of an IntSummaryStatistics object in a specific state.
> 
> Of course. I just couldn't resist the challenge of Rémi's nice math exercise...
> 
> Regards, Peter
> 
>> 
>>> On Mar 29, 2017, at 2:43 PM, Peter Levart <peter.levart at gmail.com> wrote:
>>> 
>>> 
>>> 
>>> On 03/29/2017 06:06 PM, Chris Dennis wrote:
>>>> Remi: I really have to squint pretty hard to see that as anything other than “brute-force” - it’s still an O(N) calculation.
>>> Here's O(log2(N)):
>>> 
>>>    static IntSummaryStatistics create(long count, long sum, int min, int max) {
>>>        if (count < 2 || min == max) {
>>>            return combineProduct(new IntSummaryStatistics(), count, min);
>>>        } else {
>>>            long minCnt = (count * max - sum) / (max - min);
>>>            long maxCnt = count - minCnt - 1;
>>>            long minSum = minCnt * min;
>>>            long maxSum = maxCnt * max;
>>>            long minMaxSum = minSum + maxSum;
>>>            int mid = (int) (sum - minMaxSum);
>>>            IntSummaryStatistics stats = new IntSummaryStatistics();
>>>            combineProduct(stats, minCnt, min);
>>>            combineProduct(stats, maxCnt, max);
>>>            stats.accept(mid);
>>>            return stats;
>>>        }
>>>    }
>>> 
>>>    static IntSummaryStatistics combineProduct(IntSummaryStatistics stats, long count, int value) {
>>>        IntSummaryStatistics pow2 = null;
>>>        while (count > 0) {
>>>            if (pow2 == null) {
>>>                pow2 = new IntSummaryStatistics();
>>>                pow2.accept(value);
>>>            } else {
>>>                pow2.combine(pow2);
>>>            }
>>>            if ((count & 1L) == 1L) {
>>>                stats.combine(pow2);
>>>            }
>>>            count >>>= 1;
>>>        }
>>>        return stats;
>>>    }
>>> 
>>> 
>>> Regards, Peter
>>> 
>