RFR Re: [PATCH] 8178117: Add public state constructors for Int/Long/DoubleSummaryStatistics

[Joseph D. Darcy]

Hello,

Is it intentional that "DoubleSummaryStatistics" is used in a sentence like

   91      * @apiNote
   92      * The enforcement of argument correctness means that the 
retrieved set of
   93      * recorded values obtained from a {@code 
DoubleSummaryStatistics} source

in all three types being updated?

For the code in the constructor, if you don't want to have something 
like an explicit switch on Long.signum(count), I'd prefer to see at 
least a comment like

// Use default field values if count == 0

For the double case, I'd recommend future work change the new 
constructor to

     DoubleSummaryStatistics(long count, double min, double max, double 
sum, double... additionalSum)

where the final argument could be used to convey additional state.

For the double case, if a NaN is used than max and min will be NaN. 
Therefore, I'd recommend change the correctness constraint for that type to

     <li>{@code min} ≤ {@code max} || (isNaN(min) && isNaN(max)) </li>

with an analogous update to the code.

Thanks,

-Joe

On 10/30/2017 3:49 PM, Paul Sandoz wrote:
> Hi Chris,
>
> After some hiatus here is an updated webrev, i made some tweaks to the 
> JavaDoc:
>
> http://cr.openjdk.java.net/~psandoz/jdk10/JDK-8178117-summary-constructors/webrev/ 
> <http://cr.openjdk.java.net/%7Epsandoz/jdk10/JDK-8178117-summary-constructors/webrev/>
>
> And the CSR:
>
> https://bugs.openjdk.java.net/browse/JDK-8190381
>
> The support for a double sum of consisting of an array of double is 
> going beyond my complexity budget for this feature. If that is deemed 
> important later on we can add another constructor.
>
> Paul.
>
>> On 11 Apr 2017, at 17:44, Chris Dennis <chris.w.dennis at gmail.com 
>> <mailto:chris.w.dennis at gmail.com>> wrote:
>>
>> Updated patch with the changed parameter validation, updated javadoc 
>> and added test coverage.
>>
>> <8178117.2.patch.txt>
>>
>>> On Apr 11, 2017, at 4:48 PM, Chris Dennis <chris.w.dennis at gmail.com 
>>> <mailto:chris.w.dennis at gmail.com>> wrote:
>>>
>>> Color me confused… what would the javadoc on the parameter say? It 
>>> could I guess have an @implNote documenting the meanings of the 
>>> parameters… but then what use is it? The proposed API simply limits 
>>> the precision with which a DoubleSummaryStatistic can be copied to 
>>> be the same as the precision with which it can be “accessed”.  That 
>>> doesn’t seem an enormous problem since I suspect that bulk of usages 
>>> would be to marshall a “finished” instance and therefore there is no 
>>> real loss occuring. If we wanted to support arbitrary precision 
>>> wouldn’t it be better to have a constructor variant that took a 
>>> BigDecimal, and a matching getPreciseSum() that returned a BigDecimal?
>>>
>>> Chris
>>>
>>>> On Apr 11, 2017, at 4:16 PM, joe darcy <joe.darcy at oracle.com 
>>>> <mailto:joe.darcy at oracle.com>> wrote:
>>>>
>>>> On an API design note, I would prefer to DoubleSummaryStatistics 
>>>> took a double... argument to pass in the state of the summation. 
>>>> This flexibility is necessary to more fully preserve the computed 
>>>> sum. Also, the we want flexibility to change the amount of internal 
>>>> state DoubleSummaryStats keeps so we don't want to hard-code that 
>>>> into as aspect of the API.
>>>>
>>>> Thanks,
>>>>
>>>> -Joe
>>>>
>>>>
>>>> On 4/11/2017 12:53 PM, Paul Sandoz wrote:
>>>>> Hi Chris,
>>>>>
>>>>> Thanks for looking at this.
>>>>>
>>>>> There is some rudimentary testing using streams in 
>>>>> CollectAndSummaryStatisticsTest.java.
>>>>>
>>>>> I think we should enforce constraints where we reliably can:
>>>>>
>>>>> 1) count >= 0
>>>>>
>>>>> 2) count = 0, then min/max/sum are ignored and it’s as if the 
>>>>> default constructor was called. (I thought it might be appropriate 
>>>>> to reject since a caller might be passing in incorrect information 
>>>>> in error, but the defaults for min/max are important and would be 
>>>>> a burden for the caller to pass those values.) In this respect 
>>>>> having count as the first parameter of the constructor would be 
>>>>> useful.
>>>>>
>>>>> 3)  min <= max
>>>>>
>>>>> Since for count > 0 the constraints, count * max >= sum, count * 
>>>>> min <= sum, cannot be reliably enforced due to overflow i am 
>>>>> inclined to not bother and just document.
>>>>>
>>>>>
>>>>> Note this is gonna be blocked from pushing until the new 
>>>>> Compatibility and Specification Review (CSR) process is opened up, 
>>>>> which i understand is “soon"ish :-) but that should not block 
>>>>> adding some further tests in the interim and tidying up the javadoc.
>>>>>
>>>>> Paul.
>>>>>
>>>>>
>>>>>> On 6 Apr 2017, at 07:08, Chris Dennis <chris.w.dennis at gmail.com 
>>>>>> <mailto:chris.w.dennis at gmail.com>> wrote:
>>>>>>
>>>>>> Hi Paul (et al)
>>>>>>
>>>>>> Like all things API there are wrinkles here when it comes to 
>>>>>> implementing.
>>>>>>
>>>>>> This patch isn’t final, there appears to be no existing test 
>>>>>> coverage for these classes beyond testing the compensating 
>>>>>> summation used in the double implementation, and I left off 
>>>>>> adding any until it was decided how much parameter validation we 
>>>>>> want (since that’s the only testing that can really occur here).
>>>>>>
>>>>>> The wrinkles relate to the issues around instances that have 
>>>>>> suffered overflow in count and/or sum which the existing 
>>>>>> implementation doesn’t defend against:
>>>>>>
>>>>>> * I chose to ignore all parameters if 'count == 0’ and just leave 
>>>>>> the instance empty. I held off from validating min, max and count 
>>>>>> however. This obviously 'breaks things’ (beyond how broken they 
>>>>>> would already be) if count == 0 only due to overflow.
>>>>>> * I chose to fail if count is negative.
>>>>>> * I chose to enforce that max and min are logically consistent 
>>>>>> with count and sum, this can break the moment either one of the 
>>>>>> overflows as well (I’m also pretty sure that the FPU logic is 
>>>>>> going to suffer here too - there might be some magic I can do 
>>>>>> with a pessimistic bit of rounding on the FPU multiplication result).
>>>>>>
>>>>>> I intentionally went with the most aggressive parameter 
>>>>>> validation here to establish one end of what could be 
>>>>>> implemented.  There are arguments for this and also arguments for 
>>>>>> the other extreme (no validation at all).  Personally I’m in 
>>>>>> favor of the current version where the creation will fail if the 
>>>>>> inputs are only possible through overflow (modulo fixing the FPU 
>>>>>> precision issues above) even though it’s at odds with approach of 
>>>>>> the existing implementation.
>>>>>>
>>>>>> Would appreciate thoughts/feedback.  Thanks.
>>>>>>
>>>>>> Chris
>>>>>>
>>>>>>
>>>>>> P.S. I presume tests would be required for the parameter checking 
>>>>>> (once it is finalized)?
>>>>>>
>>>>>> <8178117.patch>
>>>>
>>>
>>
>